996 cam timing after IMS install question

2003 996 C4S 60,000 miles It was time for a new clutch. I installed a LN IMS bearing and rear main seal while I was there. Both original bearing and seal looked perfect. I locked the intermediate shaft with the 3 allen stud bolts. No way it moved ! It didn't even shift side to side, new bearing and cover went straight on. I looked at the cams at TDC and marked them when I installed the 3 set screws /allen bolts. After installing the tensioners I rotated the engine 360. One of the cams is off. The lower cam on drivers side. Viewable from rear of the car. I assume its the 1-3 exhaust but haven't taken the time to look that up. At tdc all cams notches are straight up and down except for one. Its rotated about 10 degrees. 1/8" from straight. I will try to get a picture. I can't believe it jumped a tooth. Ideas please ????????

I think you need 720 to get #1 at TDC again. (4 stroke engine) Rotate it 360 again and see where they are.

Absolutely the cams can move when using that locking approach. Why? Because nothing is mechanically locking the cams, only the IMS assembly. On any 3 chain engine chain wrap makes all the difference. This happens on exhaust cams more than intakes.

Thanks for the replies. I went another 360 and it's still off. I would have gladly locked the cams, had I known there was a chance of something moving. The instruction guide I was using only mentions the allen studs. What's the best way to proceed ? Cam timing procedure per manual or can I just pull oil pump and rotate the exhaust cam?

Typically when something like this happens you already had a problem, it just wasn't noted yet. Typically this issue is related to a stretch chain, or an IMS drive that has slipped on the shaft. This is why we urge professionals to do this job, so cam timing deviations can be checked while the engine is being qualified for the retrofit procedure. Its imperative to know if you have issues BEFORE you pull things apart. Can you get pics of how far out that exhaust cam is with the crank locked at TDC? I need to see if its advanced or retarded, because that makes a difference in how you'll bail yourself out of this predicament. This is why I have three IMS Chapters in my book, two of which are dedicated just to IMSR and specifically for 3 and 5 chain cam timing.

Thanks Jake Here's a picture, while locked at TDC . I did check location of cams before removing tensioners. They were all straight up and down.

Wow! To move that much that cam had to be "on lobe" and that's what happens when chain wrap enters the equation. Can you get a pic of the ends of both cams in the same shot?

I'll try for a photo tomorrow. The top cam is straight up and down / parallel with split line in case. I'm not sure if it's possible but the more I rotate the engine the worse off center it gets. It was only an 1/8 off before I rotated 720.

I need to see something else from that photo :-)

Jim, not sure how you missed all the previous posts about locking the cams and NOT using the set screw method. Many of us have done the IMSB as a DIY job. Now the good news is that since your a DIY guy, dropping the engine and trans is really not hard at all and some of us have some DIY's, tips, and shortcuts learned the hard way.

"This is why I have three IMS Chapters in my book, two of which are dedicated just to IMSR and specifically for 3 and 5 chain cam timing." Available for purchase? Where?

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I can't believe I missed it either. I really did spend a week googling everything I could find for trans removal and IMS replacement. I guess I should contact the author of the instructions I used and let him know, not so good. I'm currently researching how to fix my problem. Not having much luck. I gather, so far, that I can remove oil scavenge pump on bank 1-3 and loosen 4 bolts on exhaust cam sprocket. I looked at the pump on car and there's not much room. I'm trying to figure out if the pump can be removed while engine is in the car. I read remove with tensions installed and don't remove with tensors installed. I like to work on my own cars. I really don't trust "other" mechanics. Like you say, live and learn. At least I didn't cause irreversible damage ....... yet.

Jim, no need to panic or get in a hurry. I would not attempt this with the engine in the car. It is so much easier to work on when dropped. Most dont believe how easy it is until they drop it themselves. You can also do the chain guides and chains if needed. Four full size jack stands, ATV/motorcycle jack, trans jack, two regular hyd jacks, few wood blocks, and you got it. Airlift to vacuum refill coolant is helpful. It was the most fun DIY I have done on my car and really gave me a chance to replace many parts and thoroughly go over the engine. 47" from floor to top of rear fender well gave me more than enough room. My engine is now completely leak free and runs fantastic. Please keep us posted.

You might get away with just lowering the engine a bit. I haven't yet done this but will in the spring when I'm replacing the vario cam actuator.

What happened or just for PM? Isnt that the $$$$ part?

I agree that pulling the engine is easier and is required for access to the bank 1 components in a 996. Bank 2, on the other hand is very simple to do in the car as direct access is no issue. I believe I can bail him out by simply keeping the crank locked, loving the intake cam and then pulling the scavenge pump, and loosening the 4 bolts on the exhaust cam drive. Then the offending cam can be rotated back into place, cam lock fitted between both cams and the cam drive bolts re-tightened. Thats why I want to see a pic of both cams in relation to each other on that side of the engine. Some improvising may be necessary and rules may need to be broken, but we should be able to accomplish this with the cam cover in place. While the scavenge pump can be pulled from 1-3 with the engine in the car, you will waste more timing trying to avoid pulling the engine than you will just sucking it up and pulling it. This is precision work and you may have to fight to get things back in place, and you don't want anything in your way.

Update. I locked the exhaust cam, bank 1-3 Removed the four bolts from the oil scavenger pump ( all driver side stuff) The pump almost comes all the way out. I was able to loosen the four bolts that hold the gear onto the exhaust cam shaft. The gear is slotted to allow some fine adjustment. I guess. With gear loose I rotated crank until four gears bolts were against the end of the slot. There wasn't enough available adjustment to get the alignment back to perfect. But it's a lot closer. I guess it skipped a tooth. I removed both tensioners on the flywheel side hoping there would be enough slack in the chain to jump back a tooth but no dice. I guess I would have to remove cam covers to move the exhaust cam back a tooth.

You are fighting yourself with the engine in the car. Trying to reinstall the scavenge pump and realign the drive will make you beat your head against the wall, if you do get that far. I also believe that you skipped a tooth, but you should have heard that occur. Chain wrap will show you who the boss is! Post some pics of what you have now. Remember, you may need to pump the tensioner back up before you can set final cam timing, else it will be out as soon as the engine fires up and gets oil pressure.

Here's a current pic of exhaust. The intake is straight up and down. Sorry for the blur.

And the sprocket is at full advance, correct? You still have the crank locked? How does things look on the opposite side?

Yes full advance. crank locked. Opposite side is fine. lockout tool fits the opposite side. Am I close enough ? lol

You can still save this with the engine in the car, but on that bank it will be tough. You will have to remove the cam cover, remove the sprocket, advance it one set of teeth and reinstall. There is enough room to drop the sprocket off the cam, shake the chain loose, reset it and reinstall within the confines of the chain well. One more question, is the tensioner in or out right now??

Thanks for the info. The tensioner is installed.

Pull the tensioner and see if you can get any more adjustment.. You may be able to unless my eyes and mind are playing tricks on me.

Success ! Well maybe. I loosened the tensioner and rotated the cam with a tool I made. Reinstalled the tensioner, rotated 360 and all the cams look good. I installed the green cam caps, added oil and fired it up. Sounds good, no check engine light, ..... Yet. Road test tomorrow. Thanks Jake and everyone else who replied.

Wonder how I learned that trick? :-)

Well done for the both of you.

I wish you took a photo of the smile on your face when it was all lined up again. I couldn't imagine how relieved you felt

Actually , I did snap a photo. My friend didn't believe I drove back down to the shop so quick to try out the socket. Otis was happy too.

You are so lucky that worked out for you. Im sure the great guidance from Jake helped. Good job!

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Hahaha! Great!!

Happy New Year ! I'm glad my skipped tooth is a 2013 item. I got the engine light after a 30 minute drive. I connected my durametric and it shows misfires on cylinders 1 to 3. The live logging shows constant misfire on 1-3 . 4-6 are 0 misfires. Sooooooo. Here's my next question. Is the skipped tooth between the 2 cams or is it the gear and chain from the ims to exhaust? Probably a dumb question but I really want to get as much info before I dive in.

You need a scan tool that will show cam deviations.. You probably have the timing good enough for the engine to run ok, but it's out far enough to create a code from mode6 data after it ran long enough. A CEL will pop if you are only 7* out. Let me guess this CEL popped just after start up, maybe within 2 min?

It took a while for the light to come on. I idled the car for 20 mins. Drove on the highway for 15 mins. Restated the car for the 3 rd time and it came on. I hooked up my laptop to see the code. It's was misfire. I happen to look at cam deviation and it was 2.0 on both cams ?? I think. I really didn't know what to look for at the time.

Yep. It's barely out.. What codes did you have? You may have pending codes on mode6 for cam timing, but it's out far enough to pop misfires. 2.0 degrees is enough to cause this.

Okay, I fixed it again. Jake was correct , just out far enough to cause misfires. I must mention that I have a four post lift. Makes all this work a little easier. Today I pulled the oil scavenge pump. Drivers side bank one. I loosened the front motor and rear Trans mount. The pump won't come out unless you move engine to rear of car. Create some clearance. I locked at tdc. I took bank one tensioner off. The one right next to bank one exhaust cam. I removed the four bolts off the exhaust cam gear ( though the oil pump opening ). Rotated crank until I could lock the exhaust cam. Rotated crank back to tdc. Now both intake and exhaust were straight up and down. I removed the gear off the exhaust cam and moved it a couple of teeth. The four bolt holes are now centered within the slotted adjustment range. Put lock-tite on the four cam gear bolts and snugged them down. Replaced tensioner and spun 360 to see if slots on all four cams look good. All good. No miss-fires. 1.8 cam deviation runs smooth. Went for 45 road test. I think I'm good.

Great way to start the new year!

Cam timing is a precise setting.. Just a couple of degrees will make an impact on the engine. Its possible that you have it in close enough now to not throw a CEL, but you may still get crappy fuel economy from it. 1.8 degrees is still almost twice as much as we shoot for, but sometimes its all you can get.

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Doesn't look like its working on the passenger side. I don't think it ever did for me since the code was stored when I picked up the car as a non runner. That code came back shortly getting the car back on the road again. Yup its pricey but oh well.

Glad to see this got resolved. Nice work Jim and impressive that you fixed it up without pulling the engine. I've got a very similar situation happening on my car. I replaced the IMS and the car ran like poop upon startup. At first it wasn't throwing codes, which was really bizarre given how much it would sputter, shudder and backfire. I inspected the timing and it seemed spot on to me. Started it up again and saw the codes pretty quickly. Random engine misfire P300 and then specific codes for cylinders 1,2,4 and 5. Given what I saw with the timing, I though perhaps the coil packs were going out so I changed them and am still having the same problem. Very interested to know which values and parameters to log in Durametric to determine how far off the cam timing is. I think I've got a five chain motor (2001 C4) so I didn't expect the engine timing to slip given the precautions during the work performed.

With all the info out there about doing the IMSB I gotta ask again, why are you guys NOT LOCKING THE CAMS? Sorry, hope you get it worked out.

You want to look at the Durametric actual values camshaft deviation .(I think the spec is + or- 6) .Another candidate would be the crankshaft position sensor since both banks are acting up .

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I made the mistake of following the "Pelican Parts " dyi instructions. A nice write up with lots of pictures. Too bad it provides BAD instruction.