CEL: Engine stumbling stuttering and wanting to shut-off

Well, I�ve just completed my 1,700 mile journey in my �99 996 over the last few days. With only 10 miles to my destination I felt the engine stumble and stutter which was immediately followed by a flashing CEL and then a steady CEL. When this happened I quickly pulled the car over so I can inspect the engine. Nothing appeared wrong. No smoking. No leaking. Nothing. I realize this was probably very unwise but since I was stuck on a two-lane canyon road, I decided to re-start the car and very very carefully drive/limp to my destination, which I did. The car feels like it has a misfire and isn�t running on all cylinders. To keep the car from stalling and shutting off, I had to keep it in low gears and maintain roughly 3-4k rpms. Furthermore, the engine doesn�t seem to be responding to throttle inputs reliably. All instrumentation reads good, except for the CEL and engine behavior. Any ideas? Vacuum leak? Thanks in advance. Mike

Perhaps it is worth mentioning...the car was running fantastic 99% of the drive. I was getting over 370 miles per tank (with a couple gallons left to spare) and 26+MPG. Mike

Get the code read and that will send you in the proper direction.

^^^^ I have scanners but, unfortunately, I don't have those tools...or any of my tools, with me. Quite frustrating! Mike

go to o'reilly's ...they loan out a scanner for free. Good luck!

Good idea. I'll have to research which auto parts stores are in the area since I'm not too familiar with this part of Washington state. Mike

Don't drive it until you get the codes read. You don't want to cause any unnecessary damage.

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No, agreed! I wasn't planning to and I'm not driving the car back to CA. It will be staying here in Washington. I'll be moving here next month (at least I'll have tools here soon, lol). Mike

As mentioned, get the CEL code and share with us so you can at least have an idea what is going on.

I hope it's something simple like a coil or coil wire. And for the future, pick up a cheap Bluetooth or WiFi code reader and keep it in the car.

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Will do. I'll report back as soon as I can read the codes. If I can't get access to a code reader here, I'll be back in WA in a couple weeks. Me too!!! I have two code readers. One, is in my Mercedes. The other, in my tool box. And both, are in CA. I'll be putting the reader that's in the Merc, in the Porsche for now on. Mike

Was it raining?

^^^^ No rain. Slightly cloudy. Surprisingly, I only hit rain in Utah. Mike

Any update on this Rdrcr?

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Soon. I'll have an update on the codes this Friday/Saturday. The car is in Washington and I'm on my way there tomorrow...with TOOLS!!! Mike

Update: P0300 P0301 P0302 P1316 Mike

I should have time tomorrow to pull the coils and plugs. Anything else I should be looking at? Mike

I installed the new spark plugs and ignition coils, unfortunately, that didn't solve the rough running and idle issues. Three of the spark plugs smelled of fuel. #1 spark plug was pretty black and wet. Three of the coils had minor cracks. Upon restart I can smell fuel. What are we thinking? Vacuum leak? Mike

So where in WA are you headed,, ?? Just curious...

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Olympia. Mike

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Just a wild guess. Injectors? I would replace them. Bad ones will cause bad things... I'd also wait for someone smarter than me to chime in.

^^^^ I'm sure it wouldn't be a bad idea to replace them. However, I don't think the injectors are causing the problem. I'm gonna dig around under the hood here in a couple hours to see if I can visually identify any potential vacuum leaks. I'm just not sure what else would cause what I believe to be excess fueling in the cylinders. Just before this incident happened, the car was running flawlessly. I was even getting close to 28mpg on the highway. Crazy! Mike

I have a '99' as well. Our cars are probably in need of injectors. Yours sounds as if the injectors may be leaking at rest and or idle if your plugs are wet. Raw gas isn't benefitial to spark plugs. If you have a pressure gauge hook up to test port on fuel rail passenger side and remove vacuum line from regulator. If pressure increases your diaphragm is intact if not your regulator.should be replaced. At idle engine doesn't need as much fuel as it does at higher RPMs.

^^^^ Thanks for the suggestion. And, I don't doubt that I may need injectors. I have a vacuum gauge. However, I can't get the engine to idle. It'll start, stumble and shut off. Any suggestions on being able to perform the test under these conditions? Mike

QUOTE=Rdrcr;15930057]^^^^ Thanks for the suggestion. And, I don't doubt that I may need injectors. I have a vacuum gauge. However, I can't get the engine to idle. It'll start, stumble and shut off. Any suggestions on being able to perform the test under these conditions? Mike[/QUOTE] Your injectors are 20 years old...Don't doubt them possibly needing replacement. JR spoke in depth about them causing issues as they've aged. Air filter clean?

^^^^ Air filter is clean. Trust me, I don't have any issues with replacing 20 year old injectors. However, I don't want to throw parts at the car attempting to diagnose a problem. I want to positively identify the problem, resolve it, and move forward with additional preventative maintenance. Mike

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I totally get that. Good luck!

Unplug the MAF sensor on the airbox and see if the idle changes. Also might consider disconnecting the battery neg terminal for 30 minutes and that will reset the DME/ECU to default base values. When was the last time the TB was cleaned,...and the Idle Control Valve (if you have cable throttle)? Check the clamps on the main air box hose...make sure they are tight.

In one of Jake Raby's videos he stresses making sure your coil pack connectors are firmly seated. Might be worth a double check.

I was going to suggest unplugging the MAFS. That will help you determine if the MAFS is bad or if the air intake tubes have holes in them. Then check the Idle Air Control Valve (just had this issue on my BMW 330i) Then check to see if the alternator might be bad or the belt might have broken. Then check the coil packs and the connectors. I hope your timing chain didn't break.

Does anyone read between the lines anymore?

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Thank you for the suggestions. I'll give this a shot. The TB is pretty clean. However, I can see a film of fuel/oil in the manifold. I'll take a look at the idle control valve. All the hoses and clamps are pretty tight. I saw that. Yes, after I installed the new plugs and ignition coils and restarted the vehicle with the same results, I went back to check the connectors. They are all firmly seated. Alternator is good and belt is good. Coilpacks and connectors are good and firmly seated. I'll follow up regarding the MAF and IAC. Man, I hope the timing chain didn't break either... Mike

I reset the DME/ECU and started the car. It idled poorly for about 30 seconds and disconnecting the MAF made no difference. I could smell un-burned fuel. Could these symptoms be a sign of an AOS going bad? Mike

Not the AOS. Back to a vacuum leak or something else...fuel pressure regulator?

^^^^ Thank you for the pictures! I'm somewhat familiar with the vacuum lines after performing the starter, alternator and the starter/alternator cable replacement a couple years ago. I did have the vacuum lines and rubber replaced about a year ago by a local Porsche repair facility. As suggested I've taken a look at the vacuum lines...not extensively, however, as I haven't removed any parts yet...but they all look attached and in good condition. Mike

Smoke test it.

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I'm leaning that way. I have an appointment with Dundon Motorsports for diagnosis and perhaps, repair. Mike

Then you're in good hands, best of luck!

^^^^ I'm fast approaching my limits of skill and means to further diagnose the issues I'm experiencing. I think this is the best option, albeit, more expensive. Regardless, I'll report back with the diagnosis and results. Mike

With a P0300, P0301, P0302 and a P1316...anyone think that this could be a camshaft solenoid valve causing the issue(s)? Mike

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No, I don't. I know you want a positive diagnosis of the problem before any major steps are taken, but sometimes a failure just doesn't cooperate with the easy normal diagnostic routines. From reading through the posts I think you have an injector spraying/leaking when it is not suppose to..

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Thank you for your response. That's interesting...good to know. Several members have suggested injectors. Yes, I definitely want a positive diagnosis before proceeding to fix the problem. I do have an appointment for diagnosis/repair but, I don't take the car in for another week, so it's going to continue to bother me until the car is in the shop, lol. If it is injectors...do you recommend replacing all six? Mike

Yes, all 6!

With 100% new NOT remans. It has beed talked in depth and even though the remans r tested they may not perform the same under load and these cars need good fuel delivery.

I'm all for replacing with new. Want to find out if there is a supplier that offers new injectors for less than $78.03 each. That price doesn't include O-rings. Appreciate any replies..

Who's offering NEW injectors? Most of the injectors I've researched are reman? Mike

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https://www.ebay.com/itm/362165816870

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Dang. I have a 1999, those injectors are for the newer 996. I haven't been able to find new injectors for my year. Mike

This is what I have come up with for a '99' Carrera. oemexoticaauto.com P/N : 996-606-120-01 Might need to ask the group in a new thread. Otherwise we may not have too many choices. One more......porschepartsnationwide.com

Jake said he uses the new injectors on the 3.4 engines, they just need a retaining ring modification or something of the sort. He said he was going to do a video on it, but he didn't do it. BTW, I bought six used injectors for a 3.4, was going to have them rebuilt and started a thread about it, that is when they said don't rebuild them, go with new. If you wanted them for testing or putting in your car, I would be happy to help out and ship them out to you, just pay shipping, if interested, PM me. Here is the thread: https://rennlist.com/forums/996-foru...-my-motor.html

Paul, Did you ever take the plunge and order new injectors for your 996? If so which ones the 996.1 or .2 and which vendor. Thanks for any reply..... happy 4th.

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No....never did it. I was going to get 996.2 injectors, but was waiting for Jake's video....and like everything, got side tracked.

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I saw Jake's video too. That's main reason why I was looking for new injectors. I didn't know he was modifying newer 996 injectors to fit the 3.4. I'll be looking forward to watching that video. Thanks for the suggestion. If I was sure that the injectors are causing my issue, I'd take you up on your offer but, since I'm unsure at this time. I'm just gonna let Dundon perform the diagnosis. I'm hoping the issue is something reasonable...like injectors, lol Definitely looking forward to this information. Mike

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I'm sure it wouldn't be hard to figure out...Get a set, compare the two and get er done! If anyone has some old injectors send one to me and I'll figure it out.

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Great minds....? I offered the same thing if someone wanted to send me a 996.2 injector, but nobody ever took me up on it. I have a full set of used early injectors (from a '99) and I'll send you one if you want. Private message me.

Okay, when comparing injectors for the '99' 996 it seems that there are two iterations of the 996-606-120-01. The earliest has the blue colored connector body and the second has the light green. Where 2000 996's should only use the green. Earlier '99's can mix and match. Then there is the white injectors #996-606-122-00. All the parts vendors list that one as not fitting a '99'. This one is the least expensive at around $57.00. The others range from $76.71 to $157.00 or more. My local Indy thinks the white one won't fit the '99'. Would be great if you guys can get these to work though. A set of 'O'-rings is a little over $100. Think I'll go for the tune up in a can for now.

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O-rings are a few bucks only. NAPA rebuilt mine for $115.00

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Thanks! I would need one of each. Once I get a new set of .2's Ill be able to compare with a spare.

^^^^ Keep us posted! Mike

Dundon Motorsports has confirmed the issues my car is experiencing. They will be performing a leak-down and compression test. I'm hoping to get news tomorrow. Fingers crossed for something simple/inexpensive... Mike

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Best of luck!

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See below... Mike

Zero compression, cylinder #1. After checking the engine with a borescope, they believe the intake valve spring for cylinder #1 is broken. The engine will need to be removed to fix the issue. I'm awaiting my quote for the repair on Monday. The good news...no bore scoring and everything else seems to be in great condition!!! A broken intake valve spring, or any valve spring in general for these engines seems pretty uncommon. However, I have read of a couple examples... I'm assuming the engine does have to be removed to repair a valve spring, correct? Do the heads need to be removed for this repair? Any thoughts? Suggestions? Mike

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0 compression/broken valve spring, interesting. It's not very common but does happen from time to time. I can hear a 0 compression from listening to the engine spin on the starter before cranking. The starter speed will noticeably increase for an instant as the effected cylinder is suppose to be on compression stroke. I then do the compression test only to verify which cylinder it is, then do a leak down test to determine where the lost compression is going, (ie intake valve or exhaust valve or crankcase/piston.) With the right tools , the heads don't have to be removed or the engine removed. Just the cam cover, cam, lifters, and lifter carrier.. I prefer to do it with the engine still in the car (just lower the effected side), but a lot of techs prefer to drop the whole engine/trans assembly..

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Great info! Thank you for your post! Do you believe that techs like to remove the assembly in case there may be other issues/damage? Planning ahead? If the engine does come out, do you recommend any preventative maintenance? Mike

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No, I think it boils down to personal preference. If I were planning to do 1 valve spring, AOS, water pump, coils/plugs on a 996.1 or 986, I would just do it with the engine still in the car, just lowered a bit. To me enough room, is enough room. With the right tools, I can do these with much less work/time than dropping the whole engine/trans unit and THEN STILL having to perform the necessary replacement routines. Whether the engine is sitting on a lift table or still in the car on a lift , makes little difference to me on those operations. If you add a clutch/flywheel, RMS, IMS, or it's a Tip or a 996.2 AOS, or a 996.2 valve spring, that changes everything !! Then I would prefer to have the engine/trans on the lift table. All maintenance is preventative maintenance, I think there is no such thing as over maintaining your car. Do as much as your heart/wallet will allow..

Sorry, but glad you got it finally figured out and it's fixable.

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As you say, if the engine comes out...and I can afford it, I am considering a new clutch, AOS, RMS and IMS 'solution' installation. But, that'll all depend on the quote. Are 'newer' 996.2 valve springs any better than the 996.1? Me too! Much agreed. Mike

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No, and they wont fit the 996.1 either. They do occasionally break as well. The reason I say that the engine is to be removed on the 996.2 is the different cam set-ups, 996.2 has vario-cam plus. The cam timing tools are much larger and you can't use them with the engine still in the car like you can on the 996.1. The large torque-to-angle bolt and the holding tool cannot be used with the engine still in the car.. Like I said 996.1 is much easier and can be done with the engine still in the car, but a lot of techs just pull the engine/trans same as the 996.2, they don't differentiate.

^^^^ Gotcha! I'm following you now. Thanks for the additional explanation! Mike

A broken valve spring is very uncommon, the valve train on this engine is a quite low tention set up, a more common problem is a loose valve seat , probably not allowing the valve to close . First job would be to just remove the valve cover, you can then check springs but I would bet you might see a valve partially open, this will then require removal of the head to inspect and repair the seat. Hope you get it sorted!

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Thank you for your post! From what I've been told, yes, the valve is partially open. I'm hoping to get it sorted too! Mike

Okay. Engine is coming out! My car is a early '99 with a '98 build date. Should I be considering a LN Engineering IMS retrofit kit bearing for my engine while it's out? I'm also considering a new AOS and clutch while the engine is out. Thoughts? Mike

Yes, you should! Do it once and do it right. The IMS Solution is the only one I'd consider. Should you ever sell the car, you will get your money back. Should you keep the car, you'll never have to go back in and do it again.

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We did discuss installing the solution and I would agree that logically, that's really the only way to go. However, I'm trying to save as much money as possible...I know that doesn't sound wise in this situation but, I hadn't budgeted for this unforeseen engine issue so I have limited funds available. The solution is roughly a $1K more than the retrofit and hours more in labor. I want to do as much as I can while the engine is out, but within reason. I'm figuring that the most important items to address are going to be repairing and replacing the damaged and wearing components of the valvetrain and do as much extra as I can afford while the engine is out. My goal is to keep the vehicle on the road until I can afford a full rebuild and displacement increase. Mike

I would think the LN IMS Retrofit would be a good choice if you're working within a budget. While the LN Solution would be great, the Retrofit has been working well in a lot of engines. It buys you a few years to decide if you want to do another Retrofit or the Solution at the next service interval.

^^^^ That's what I'm hoping. Mike

Do you know the S/N of your engine? May not be the cars original? That might make a difference.

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Yes! M96/0166X06876 I'm pretty sure that's the original. 1 owner car before I purchased with all service history. Mike

Okay,. That number looks correct for a '99'. Sounds as though you have all the records for your car so you would know what has and hasn't been serviced. Don't know your mileage, also not sure if anyone advocates replacing the dual row

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I just turned 100K miles. The factory IMS has never been replaced and that's precisely, why I'm asking 'IF' I should even consider replacing an OEM dual row...LN Engineering suggests that the IMS bearings is a serviceable item and should be replaced every 6 years or 75K miles. If that's correct, then I'm assuming I 'should' replace it. Mike

Personal decision. I'd look at the probability of an adverse event and the impact if it happens to figure out the risk. It may be low likelihood, but the cost to repair/replace is high. For me it is worth the cost of a periodic bearing replacement to mitigate that risk.

^^^ And, that's kinda what I'm thinking. We're gonna take a peak at the 100K mile OEM clutch. I'm thinking if the clutch needs to be replaced...a new IMS bearing will be going in. Just like a new AOS... I just want to make sure I'm not crazy if I replace a factory dual row for an aftermarket bearing... Mike

Just change it, it's not worth the risk and clearly you're not in a financial situation to do a full rebuild should it fail. What's your budget for all this? I know of a 40K mile 3.4 that's still in a car running well if needed.

^^^^ Thanks for the suggestion! I believe we're gonna be right around $7K with all the work going into the engine (all new valve springs, all new lifters). Mike

Update: I stopped by Dundon Motorsports this morning to survey the top-end damage. One intake valve spring is in fact broken. One intake valve is bent. And, the Oil Scavenging Pump is broken (the drive shaft broke off in the camshaft). Jacob told me I'm lucky. He's never seen one of the oil scavenging pump break like this and not destroy the engine! So, next, the head is coming off for further inspection and I do have some timing chain guide wear. So, those will be replaced too. In addition, the clutch, flywheel and slave cylinder require replacing as does the nasty looking AOS. Mike

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I have seen the scavenge pump drive break off quite a few times, but he is right, you are very lucky, more commonly when a piece of valve spring or ect. locks the scavenge pump,the timing chain will break or the IMS gears will slip on the shaft , this causes pistons and valves to collide and catastrophic failure immediately !! Since having the scavenge pump drive break is really the best case scenario, I have often thought it would be best to cut a fault line across the scavenge pump drive to ensure that in the event that the pump locks, the drive will break instead of the timing chains and IMS , sort of a "mechanical fuse" if you will, to protect from catastrophic failure. The scavenge pump is very easily replaced...

^^^^ I was wondering which failure occurred first but, yeah, that makes sense. I know the valve spring keeper(s) are missing, the retainer looks like some material has been removed and who knows how many small pieces came off the valve spring. So, I could definitely see any of that material locking up the scavenging pump. Dang. I'm glad more damage wasn't done. I'll report back once the head comes off and if there are any additional items that need attention. Plus, if I have an opportunity, I'll add pictures of what was found. Mike

We love pictures!

Broken valve spring. Mike

My two-piece valve spring. Mike

Oil Scavenger Pump drive failure... Mike

Intake valve bent, stuck and chilling in the head. Mike

You're in good hands, Dundon seems to really know their stuff. I was really impressed with what they did for Lowpue's conversion. If I had the scratch I'd have them do a custom exhaust for me.

Pull that scavenge pump apart and see what is stuck in there....a piece of valve spring or the "missing" keepers.....

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Agreed. I too was impressed and we talked briefly about that conversion. I already have a custom cat-back that's incredibly loud, has a bit of drone at low RPM but, it made great power. I'm pretty happy with it. However, with that said, I'd love a nice set of headers if I can pick up a bit more power...I hate having to spend all this money only to get it back the same, lol That's just my twisted thinking... Absolutely. I'm curious. Those two pieces are 'somewhere'. Mike

I'm thinking I have an idea of the order of events which lead to my engine issue. I've read that following a oil scavenging pump failure in the 996, in some cases (cases where the engine isn't completely destroyed by piston/valve contact), the engine will still run, but run extremely rough and will not idle. That perfectly describes how my engine ran after the flashing CEL and my engine shutting-off, which, forced me to pull off the highway. What I'm thinking, at some point during my incredibly long drive, the bank 1 cylinder 1 intake valve spring failed and the debris from that failure eventually ended up in the oil scavenging pump causing it to seize and the driveshaft to snap-off in the bank 1 exhaust camshaft leading to the CEL and engine shut-off. Just moments before the CEL and engine shut-off, I could literally feel a stutter, stumble or hiccup from the engine. And if memory serves me correctly, after leaving California, I thought the car felt a little down on power in Nevada. However, it seemed to run strong in Utah. But, getting off the Interstate in Washington I could feel that the engine was definitely down on power. My engine problems occurred 20 miles down the highway. I'm really just wondering...how long could I have driven with a broken intake valve spring and a stuck intake valve? I guess at this point, I definitely need to find out what debris is stuck in the oil scavenging pump. Metal shaving from the intake valve spring? Debris from the valve spring retainer? The two missing valve spring 'keepers'? Who knows? Mike

Heads are off. Here are pictures of the passenger side. Bores look good across all cylinders. No bore scoring on any cylinder. Mike

Wow! Looks like you really lucked out Kudos for not trying to re-start the engine... Since you're going for all that cash, don't you think it's worth an extra grand to do the IMS Solution ? One less thing to worry about down the road...

Here are pictures of the drivers side. You can see the stuck intake valve and the damage to the piston. And, a couple more pics of the cylinders... I'm being told that the piston is in good condition and can be repaired and they'll address any potential 'hot-spot' issues regarding detonation. Cylinder heads are being sent to the Machine Shop tomorrow. Mike

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Agreed. I think I lucked out too! Actually, when the failure occurred, I restarted the car and drove another 5 miles to my destination, restarting it 3 times in the process. I was lucky that when the oil scavenging pump failed (and that's what I think I felt when the engine shut off) it broke off cleanly from the exhaust camshaft and didn't cause a catastrophic failure. And lucky again that by restarting and driving the car didn't cause further damage. I won't be doing that again... Good point on the IMS... We talked about The Solution, however, I'm going with my mechanic's suggestion and installing the standard LN IMS upgrade. I know that might seem unwise while I'm already dishing out tons of cash but, the upgrade bearing will serve me well while I save money for an engine upgrade. Mike

I would not trust a piston repair at all! Think real hard on this...

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I don't think the mechanic is talking about a "repair" in the usual sense. In this case I think the "repair" just involves buffing the piston top with a scotch bright buffing disc "ziz wheel", much like cleaning the carbon off the piston top, but a bit more buffing to remove any sharp edges that could cause detonation..

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You don't think the force of the impact could cause stresses in other areas of the piston or even the rod?

" the upgrade bearing will serve me well while I save money for an engine upgrade." The beauty of The Solution is that you can take it out and use it in your "upgraded engine"... You can always throw a crappy ball bearing (just kidding) back in this engine before you sell it...

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Nope, the valve stem on these engines are very small, and the contact on the outer edge of the valve face will bend the stem very easily.\ \ Looking at the contact, it looks to be very minor. There is a lot of stress on the piston during normal operation and especially during any detonation, a lot more than this contact will produce. I have seen many forged pistons take a bigger contact than this on engines with larger/stronger valves and still not crack or have any damage/deformation. Big time damage will occur if the valve head breaks off from the stem !!!

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I'm trusting the knowledge and experience of the technician and shop regarding this repair. I did speak with a close friend whom is a former Indy Car mechanic and fabricator and is also very familiar with Porsche engines and after seeing the pictures also thought it would be perfectly fine. Like you...it's not something I think would be 'okay' but, apparently it is totally normal and shouldn't be cause for concern. Mike

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True. However, that's assuming I'm gonna stick with the original 3.4 and upgrade from there...I may do a swap...GT engine, perhaps? ...we'll see Mike

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Thanks for you input and wealth of knowledge and information! It's always much appreciated! Mike

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^^ Likely, not a good idea... Doesn't mean it can't be done but I don't think there are many GT engines floating around, and even if there are they'll cost you an arm and a leg. I would be willing to bet that if you're looking to save a grand by installing a ball bearing instead of The Solution, you're not going to drop $30-$40k on a GT (ie: a GT2/GT3/Mezger yes?) engine... ** The best bet (according to Jake Raby) for an upgrade/rebuild/swap is to always start with the original motor/platform.

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Well, the 1999 911 on the lift next to my 996, is getting a GT3 engine transplant. They've done several at Dundon Motorsports. Based on my research (considering the price I was quoted for a pre-owned GT3 engine) the swap would be roughly $5-7K more than a JR rebuild. What's attractive regarding the JR rebuild is the performance boost and having all known issues addressed...and likely the route I will be going in the future. Mike

I opt'd not to have the 'Solution' installed, so, I decided to throw a somewhat equal sum of money at something that I enjoy...Cargraphic Longtube Headers. While I highly doubt there will be any performance improvements, the gear-head in me feels much better about spending so much on simply 'fixing' something. Flawed logic...perhaps. I still have a couple weeks before the heads get back from the machine shop. Mike

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Ooooo... Those look nice! Not sure I agree with your logic, but it's your money

So, in an amazingly crappy coincidence, my 2003 Carrera had what seems like the exact the same issue about a week and half ago. I was headed home through the backwoods of Fort Bragg, NC at 65 mph in 6th gear, and suddenly I had a loss of power and CEL. It felt like the thing was running on two cylinders! I immediately thought IMS, but it was still running and maintaining 65, albeit not taking throttle well. No smoke, and it wanted to stall when out of gear or the when the clutch pedal was in. So I figured it was not the IMS since it would have grenaded itself as far as I know. I nursed it home, again coincidentally, about 10 miles. I coasted it in into my garage and had it towed to my local shop a few days later (this past Friday). Well today, I talked to the shop owner, and he said it wasn't coils (which I was hoping for), but that they took out the coils/plugs and scoped it. In cylinder 3, there are two valves stuck open. He said he saw something in the bore too, but couldn't explain it very well. I don't think he meant bore scoring though. So I'm wondering if I have the same issue? I just got my car a few months ago with 63k, and have put about 5k on it since I bought it. The shop owner said I need a new engine. What do you guys think? He didn't even really want to talk about getting into the engine to diagnose further . . . !?

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Thanks, I know. Doesn't make sense but, my mind is quite twisted. Man, I'm so sorry to hear about this. Sounds very similar to the failure I experienced. If you valve springs broke and the valves dropped, the debris from valves/retainers/springs could have locked your oil scavenging pump...just like in my case. I would suggest getting it diagnosed further to see exactly what happened. Personally, if it was me, I'd like to know what happened and what parts are salvageable and which part need to be replaced/repaired. You can always throw a new engine in there but, the actual solution may be significantly cheaper. There are options... Mike

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Having one valve spring break and a light piston tap to bend the valve is one thing (no biggie), BUT having TWO valves bent/stuck open is a sign of "chain reaction", ie. two valve springs will not break at the same time !! This "chain reaction" or collateral damage can be from minor to major. If it were me I would want to know what happened and how much "chain reaction/collateral damage" has occurred. But that's just me, I love failure analysis. I'm not surprized the shop owner didn't want to talk about repairing the engine. There is a big difference in liability for him as shop owner for installing an engine (someone else has to warranty the engine) vs the shop rebuilding/repairing the engine ( shop has to warrant the engine/repair). If the shop installs a complete engine, they are only responsible for not leaving anything loose..All the talk/publicity of these engines being prone to failure has caused this, plus many owners of these cars having high expectations of reliability also.

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I was hoping you would see my post @Porschetech3 and reply! I really appreciate your explanation for why my shop owner recommended new engine without further diagnosis, makes perfect sense from his perspective. He seems to be a good guy. I don't know that I have the funds for them to dig into the engine (labor time) only to discover that I do need a new engine. I feel like I kind of need to decide on new engine or rebuild now without being able to diagnose further the damage to my original engine. In other words, I could do one or the other, but not both. I would be screwed if I asked them to dig in, and they found it wasn't salvageable and then I didn't have enough left for a new engine. Even without them disassembling the original engine, I might not be able to afford a new engine right now! I did speak with EPS about one of their rebuilt engines. They offered to pick up my car, ship it to Miami, install an already rebuilt M97 with their upgrades (cylinders, IMS roller bearing, slightly revised geometry between the wrist pin, rod and crank, etc.) and ship it back for a what seems like a reasonablish price. What are opinions on how much this should cost?

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This is the route I'd go...if I didn't have the time/cash for a Flat6 engine upgrade and needed an engine quickly. https://lnengineering.com/rnd-store/...arrera-4s.html Sadly, looks like their prices went up $2K in the past couple months... Engine removal and install will likely be around $3K depending on the shop... Mike

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I looked very closely at this option also. If money were no object, it's the way I would go. That said, it would be several thousand dollars more (roughly $6.5k) than the EPS option. In that difference I included shipping to and from, installation and the engine itself. The wife already isn't a fan of the cost of the EPS option ($16k-ish with shipping to and from Miami from NC, installation and engine itself), so I know she wouldn't go for the LNE option. I do think IMSB improvement and the cylinders are better though with LNE. You think the EPS engine is worth that?

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I believe the LNE is the best off-the-shelf option. Is it worth the additional? Hard to say. The EPS solution looks good but, one thing that has me confused...is the steel cylinder sleeves. Originally, after reading all the horror stories on chunking and bore scoring I would have thought that this would be an improvement however, from what I've read regarding previous attempts, it isn't a good idea to use steel sleeves in an aluminum block in M96/M97 applications. Perhaps, we can get more information and clarity on this subject? Trust me, I can understand the wife...I've had those same discussions, lol. Mike

^^^^ JJM1970, here's what I've read regarding the steel/iron sleeves... https://rennlist.com/forums/996-foru...-engine-2.html Mike

Update: Both Cylinder heads are back from the Machine Shop. They look brand new! All new valve springs, retainers, keepers, exhaust valve guides and a couple new valves. They'll be cleaning up the short block this week and hopefully getting the engine assembled before the weekend. There's a possibility they'll be able to have the engine back in the car next week. Fingers crossed... Mike

Finally, my 911 is finished and back running. I decided to close out this thread with a picture when I picked it up. It's running great! I took it easy on the drive home, though. I'm very happy with all the work that was done by the knowledgeable and talented crew at Dundon Motorsports. I can post up the list of replacement components if anyone is curious. Lots and lots of parts!!! Mike

" I can post up the list of replacement components if anyone is curious. Lots and lots of parts!!!" Post it up! Looks good

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What was the price they quoted you?

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As Follows; Valve Spring...x24 Valve Spring Retainer...x24 Valve Spring Keeper...x24 Intake Valve...x1 Exhaust Valve guide...x12 Valve Sleeve Cover...x4 Engine Camshaft Lifter...x24 Camshaft Actuator 1-3...x1 Camshaft Actuator 4-6...x1 Camshaft Solenoid Cover Plate...x1 Oil Scavenging Pump...x1 Oil Pump O-ring...x1 O-ring Guide Pins...x2 Timing Chain...x1 Camshaft Gear...x2 Timing Chain...x2 Camshaft Plug...x1 Cylinder Head Gasket...x1 Cylinder Head Gasket...x1 Intake Manifold Gasket...x1 Exhaust Gasket...x2 O-ring...x6 O-ring...x6 Hex-Head Screw...x8 Water Pipe Screw...x8 Seal Kit...x2 Exhaust Manifold Bolt...x12 Camshaft Tensioner Gasket...x1 Seal Ring Coolant Drain...x1 Drain Plug...x1 Spark Plug Tube...x1 Water Pump...x1 Drive Belt...x1 Clutch Kit...x1 Pressure Plate Bolt...x8 Clutch Slave Cylinder...x1 Flywheel...x1 Flywheel Bolt...x8 LN Engineering IMS Bearing...x1 Crankshaft Seal...x1 AOS...x1 Oil Pressure Sending Unit...x1 Oil Filter...x2 Cylinder Head Machine Work (Clean, Pressure Test, Surface, 3-Angle Valve Grind)...x2 Coolant...x1 Synthetic Engine Oil...x10 Cargraphic Headers...x2 Interstate Battery...x1 & Lots of Labor... I believe that's it!!! Mike