Boxster basics - 986 Forum - The Community for Porsche Boxster & Cayman Owners

OK, had a question. My car has developed the following symptoms: When driving, especially when first engaging the clutch in first, it seems to stutter or hesitate just a little. I'll also notice it to a lesser extent in higher gears. It is also idling just a little rougher than she used to. These signs are all very subtle---If I’m not paying close attention I sometimes don’t even notice it. On acceleration under anything even close to WOT, it’s totally unnoticeable. Anybody want to give me a list of rule-outs as to likely causes of this could be? Thanks, in advance.

Sounds like it's engine (i.e. fuel/combustion) shutter/stutter than mechanical. If mechanical, I'd start by looking at engine mount and asking when clutch was last replaced and/or bled. For engine though, I'll start by asking if you recently replaced or disconnected the battery? If so, could be simply the DME relearning. If not, I assume you're not getting a CEL light? If you are, go to local parts store and have them read the code. Otherwise, I'd start by cleaning the MAF, throttle body and throttle control valve. Also, check your air fliter. By some chance something big may have gotten sucked in and is restricting the flow. Tell us more symptoms so we can point to better diagnosis

Sounds like it's engine (i.e. fuel/combustion) shutter/stutter than mechanical. If mechanical, I'd start by looking at engine mount and asking when clutch was last replaced and/or bled. No, it doesn’t seem to be ‘mechanical’ in the sense of a shudder or vibration. I’ve read through Pedro’s engine mount DIY, and the symptoms he describes don’t really fit what I’m noticing. It’s just more of a mild hesitation or roughness I hear from the engine itself. At lower RPMs, it seems to have a very subtle power loss. Acceleration at anything approaching WOT and it’s not noticeable at all. I’ve never had the clutch replaced, and I doubt the PO did either---the car had 19k miles when I got it, and it’s got about 49k now. I flushed the brakes and clutch lines a couple months ago. For engine though, I'll start by asking if you recently replaced or disconnected the battery? If so, could be simply the DME relearning. Haven’t had to replace the battery yet. I disconnected it last winter when I was doing some alternator work; it ran fine afterwards. If not, I assume you're not getting a CEL light? If you are, go to local parts store and have them read the code. Nope, no CEL. Otherwise, I'd start by cleaning the MAF, throttle body and throttle control valve. Also, check your air fliter. By some chance something big may have gotten sucked in and is restricting the flow. I took out the air filter a few days ago. There was a little bit of stuff that had been sucked up against the outer, foam portion of the filter, but the inner, pleated paper portion really looked pretty clean. I just used the shop vac on the foam part and popped it back in. Regarding the MAF, I don't really know a whole lot about it, but from what I've read on this forum I was wondering if it might be a MAF issue. Unless anyone’s got any other theories, I guess I’ll pull up Pedro’s DIY page on cleaning up the MAF, etc, and get to work. Thanks.

Also run a large bottle of Techron through it if you have not already done so..........

one more thing to consider/check - the AOS. Have you or was it ever replaced? Pull the j-tube off the side of the throttle body and see if there is any pooling of oil in it. There should be a film but no pooling in it. Also, while the car is running, try and remove the oil filler cap. If it comes off relatively easily, you should be fine. If you have to fight to get it off, the AOS could be going south. If functioning properly, the car will stumble when you remove the oil filler cap. If it runs better when removed, then you have a problem. If pooling oil in j-tube, you'll want to change the AOS PRONTO (~ $120 in parts and 2 hrs DIY). Then clean the throttle body. Let us know what you find and good luck.

X2 on the Techron; also try a bottle of gas drier such as Heet or similar. The ETOH fuels can leave you with H20 in your gas tank.

The plot thickens. Today, when I got in the car to come home from work, started her up and... flashing CEL . BUT ---only lasted maybe 5 seconds tops. Never came back on as I drove home, and we went out to eat (maybe 8 miles round-trip) without it recurring. Ordinarily, with the flashing CEL I wouldn't have driven it at all . But I recently experienced the short-lived flashing CEL (a few hundred miles ago). Talked with one guy (at an indy shop whose opinions I tend to respect) who told me to go ahead and drive her. I later took the car up to a place called Steinel's Autowerks (a place in NE Ohio that Jake and 'Phil' could tell you a lot about). The code was for a misfire, cylinder 1 , and the guy said (based on it having persisted for only a few secs that time as well) that it could have been due to a number of innocuous reasons. He reset it, told me to let him know if it came back, and suggested I run her hard on the trip back, blow things out a bit. I took his advice, and the car has been running well since---no CEL--, until the mild symptoms (running slightly rough, basically) that prompted me to start this thread. And, the brief CEL that occurred today. I'll try the Techron, etc, but for now I had the following questions: 1) Would any of the possible causes discussed so far be likely to trigger a (brief) flashing CEL? 2) If so, would the fairly straight-forward DIYs recommended here (using Techron, cleaning the throttle body, MAF, etc.) be likely to remedy the situation? I'm just trying to figure out if I should start tinkering or if, on the contrary, the problem is involved enough I should just throw in the towel and take her in somewhere to be checked out professionally. 3) Is driving the car that briefly flashed a CEL a really bad idea? (I've gotten the clear impression from folks I've talked with around here that, with it having lasted only a few secs, it's not likely at all to be a problem.) Whadaya think??

You haven't mentioned how many miles are on your car. How's your gas mileage been? Notice any meaningful reduction from what you'd been getting before this problem began? Have you considered the oxygen sensors? One or more may be iffy, but not bad enough to flash a CEL at all or may only do so intermittently. When my brother owned my '02 S it flashed a CEL at 64k miles and the mechanic replaced one faulty O2 sensor; all was good. I bought the car at 68k miles and read on this forum that it's best to change all 4 sensors at once, so I replaced the other 3 myself and the idle, while not bad before, was very noticeably smoother, and mileage improved 1-2mpg, as did overall driveability. Hooking up a code reader of some kind (I picked up a 2nd hand Durametric but haven't had to use it yet) could yield lots of good troubleshooting info. AutoZone will let you borrow a basic one for free. Based on all the things I've read on this forum I'd also look into cleaning the throttle body. My car's probably due for that now too.

Your CEL missfire on cylinder #1 could also mean a faulty plug or a faulty coil pack on cylinder #1. How many miles on either? Perhaps its time to replace plugs & check the coils for cracks and ingress of moisture.....

I tend to agree with Steve. If it is an oxygen sensor you will more often than not experience misfires in an entire bank of cylinders and a further code for the sensor. Check the code again, if it is the same code for cylinder 1 then pull out the coil pack and check it. It is a good place to start at any rate.

You haven't mentioned how many miles are on your car. But I did! It’s got 49k miles. How's your gas mileage been? Notice any meaningful reduction from what you'd been getting before this problem began? Not really sure, haven’t been paying close attention to that. (Work, family, other obligations---DISTRACTIONS! They're everywhere!) The OBC read-out is now at 19.6, but it’s been a l o n g time since I reset that. I do a fair amount of stop and go driving, with some highway time sprinkled in here and there, so I suppose that’s not too bad for a 3.2 (Right?). There hasn’t been a noticeable drop, as far as I can tell. I went ahead and reset the MPG just now. Have you considered the oxygen sensors? One or more may be iffy, but not bad enough to flash a CEL at all or may only do so intermittently. When my brother owned my '02 S it flashed a CEL at 64k miles and the mechanic replaced one faulty O2 sensor; all was good. I bought the car at 68k miles and read on this forum that it's best to change all 4 sensors at once, so I replaced the other 3 myself and the idle, while not bad before, was very noticeably smoother, and mileage improved 1-2mpg, as did overall driveability. Nope, hadn’t considered them…that’s why I have you guys! (I’m relatively new at this DIY car stuff.) Point taken, thanks. Hooking up a code reader of some kind (I picked up a 2nd hand Durametric but haven't had to use it yet) could yield lots of good troubleshooting info. AutoZone will let you borrow a basic one for free. Yeah, I thought about stopping at AZ on the way home but really didn’t have the chance (needed to pick the kid up at school). But the first time this happened (the several hundred miles ago time) the AZ code reader came up “no code”, presumably because the CEL was no longer on (which is the situation right now, as well). My regular mechanic’s equipment, while not the ‘official’ Porsche one, was more sophisticated---it gave me the misfire info. I’ll try to stop by there again and have it rechecked. Based on all the things I've read on this forum I'd also look into cleaning the throttle body. My car's probably due for that now too. That seems to be a recurring theme; I should probably do that. At 49k miles, I suppose it wouldn’t be unusual for that to need to be done, Right? (I have no idea if it was done before, but I got the car at 19k miles, and I know I haven’t done it yet.) Your CEL misfire on cylinder #1 could also mean a faulty plug or a faulty coil pack on cylinder #1. How many miles on either? Perhaps it’s time to replace plugs & check the coils for cracks and ingress of moisture..... As with the TB cleaning, gotta plead ignorance on this one, too. I only know I haven’t done anything with the plugs/coils. (I don’t suppose these are things that they would have done at the 30k maintenance---at a Porsche dealership---are they? ‘Course, that has been 19k miles ago anyway.) I tend to agree with Steve. If it is an oxygen sensor you will more often than not experience misfires in an entire bank of cylinders and a further code for the sensor. Check the code again, if it is the same code for cylinder 1 then pull out the coil pack and check it. It is a good place to start at any rate. All good stuff. Thanks. I’ll get the code read-out first and see where that takes me… BTW, if it does turn out to be cylinder 1, anyone know if that's one of the 'hard' ones or 'easy' ones to get to?

I'd probably start pulling plugs at this point. Not only are they possible culprits, but they can give you a good indication of things that are going wrong in your cylinders. I'd guess it could be one of the electrodes crapped up or it could be something simple like a loose/dirty connection in the ignition system.

49k is kind of low mileage for O2 sensors to go, but you never know. They're pricey enough to verify at least one is bad before replacing the set. Have you considered investing a Durametric? The "enthusiast" version's around $350 and it's good for 3 or 4 cars (the pro version = more $ but gives unlimited use). Software updates are free. If you're committed to P-cars for the long haul, it'll definite pay for itself and it can do and tell you so much more than a plain old code reader. Even if you're not committed or not sure, you can always sell it for at least 50% of what you paid. Got mine used for $175 with two VIN spots left. Plugs are relatively cheap @ ~$9-$10 apiece (I got OEM Berus from Sunset). If you don't know when they were last changed or it's been a while, change 'em. Some plugs are a little tougher to get at than others, but they're all really pretty easy with the wheels off. And for about $60 more you can change all your plug tubes and the inner and outer seals while you're in there doing the plugs. Mine weren't bad, but they're so inexpensive and easy to do, I figured why wait 'til they bite me. There's a good DIY article on this on Pedro's site. On the coil packs have you considered swapping #1 with another one to see if #1 still gives you a misfire code?

49k is kind of low mileage for O2 sensors to go, but you never know. They're pricey enough to verify at least one is bad before replacing the set. I'll keep that in mind. What do you think about the Daniel R comment that, if it's an O2 sensor, more than one cylinder would be involved? (Not trying to start any fights here ---just wondering.) Have you considered investing a Durametric? Yeah, I have, and I'm definitely interested at some point. (Over the last couple of months we've had an number of unusual expenses---repairs and stuff---and I really hate to invest in the Durametric right now. But, getting one is probably on the horizon not too far off. Maybe when the family asks what I want for Christmas...) In the meantime (as soon as I get the chance) I need to have someone give me a readout so I have current info. (I don't even know for sure it's still the same code as it was when I got the CEL a few hundred miles ago.) Question: Do Porsche dealerships typically charge just to plug it in and give someone a readout code?? Plugs are relatively cheap @ ~$9-$10 apiece (I got OEM Berus from Sunset). If you don't know when they were last changed or it's been a while, change 'em. Some plugs are a little tougher to get at than others, but they're all really pretty easy with the wheels off. And for about $60 more you can change all your plug tubes and the inner and outer seals while you're in there doing the plugs. Mine weren't bad, but they're so inexpensive and easy to do, I figured why wait 'til they bite me. There's a good DIY article on this on Pedro's site. Also a project I've had on the radar screen. This is the time of year I typically do this kind of project (ie when I tend not to drive the Box all that often), but I need to free up some garage space and work it into the schedule. On the coil packs have you considered swapping #1 with another one to see if #1 still gives you a misfire code? Good idea. Again, it would be nice to have the Durametric on hand when I did that...

Most dealers charge $100-150 to hook up the PIWIS.............Which is why buying your own quality scanner that can be used on any car for $100-200 starts to make sense..............