2001 996 TT Rough Idle When Cold
#16
It's almost everyday now that I mention in an email or phone call.
Replace the wideband O2's sensors at 50K miles or 10 years...
Replace the MAF sensor every 3 to 4 years..
Replace the wideband O2's sensors at 50K miles or 10 years...
Replace the MAF sensor every 3 to 4 years..
#17
Here is a good article... It sheds some light on what is happening on cold start.
http://www.pierburg-service.de/ximag...106_en_web.pdf
http://www.pierburg-service.de/ximag...106_en_web.pdf
#18
Thanks for the info Kevin.
If the throttle body cleaning didn't fix the problem, I will look into the MAF and o2 sensor replacement. Do I also need to do the downstream sensors, or just the upstream sensors?
If the throttle body cleaning didn't fix the problem, I will look into the MAF and o2 sensor replacement. Do I also need to do the downstream sensors, or just the upstream sensors?
Last edited by up4speed; 11-25-2015 at 12:30 AM.
#19
Thanks for the great description. Based on your description, the car may actually be normal because I can also explain it exactly as if the car was an old American car with a high performance cam. It feels lumpy. I also agree fully with your comparison to the Boxster because I had a Boxster S and I never had any idling issues.
I cleaned the throttle body today (what a pain in the butt! I hate working on this car!). It actually looked spotless, so it's probably not the issue. After I started it, it stumbled a little as expected since I cleaned it, but I won't know if it improved unless I start it cold tomorrow morning.
I'll report back tomorrow. If that doesn't fix it, I have to agree that it may be normal, or I may have to seek a professional that has experience with the 911TT.
One more quick question. When I put the turbo pressure hoses back on, do I have to treat the rubber o-ring with anything? A coating of oil, or maybe Molykote o-ring grease?
I tried doing a video, but it didn't really show much. The engine sounds smooth in the video and you can't see how the car has a shake. The only thing is that the RPM's vary 100rpm at most. It doesn't even seem too abnormal. It's just the shake of the car that feels abnormal to me.
I do have the Ultimate Motorwerks tune, but I don't think that it has anything to do with it because I don't remember the car doing this for the first 5 or 6 months that I've owned it (bought June of last year). I wonder if it's related to the cold weather?
I cleaned the throttle body today (what a pain in the butt! I hate working on this car!). It actually looked spotless, so it's probably not the issue. After I started it, it stumbled a little as expected since I cleaned it, but I won't know if it improved unless I start it cold tomorrow morning.
I'll report back tomorrow. If that doesn't fix it, I have to agree that it may be normal, or I may have to seek a professional that has experience with the 911TT.
One more quick question. When I put the turbo pressure hoses back on, do I have to treat the rubber o-ring with anything? A coating of oil, or maybe Molykote o-ring grease?
I tried doing a video, but it didn't really show much. The engine sounds smooth in the video and you can't see how the car has a shake. The only thing is that the RPM's vary 100rpm at most. It doesn't even seem too abnormal. It's just the shake of the car that feels abnormal to me.
I do have the Ultimate Motorwerks tune, but I don't think that it has anything to do with it because I don't remember the car doing this for the first 5 or 6 months that I've owned it (bought June of last year). I wonder if it's related to the cold weather?
Varying RPM is not what I observe with my Turbo upon any start. The idle is a bit rough, a bit raw, but the idle speed is while elevated (~1K) it is steady until after a bit of idling the idle speed slows to just above the normal hot idle speed. The idle is a bit high yet as the engine is still pretty cold.
There could be an intake air leak. If you have been at the intake system that's always a possibility. Last thing touched, first thing suspected.
You mention a tune. Tunes are "hard" on plug and make more demands on coils and even the MAF. The O2 sensors are exposed to hotter temps and while they are designed for this they can and will suffer degradation.
Last Jan. I had to O2 sensors in my stock 2003 Turbo replaced at 132K miles. The engine's behavior was a bit improved. Not oodles but I noticed it. Oh I had the sensors replaced because of a CEL once in awhile. There were as best I could tell no other symptoms. But I wanted to get the car smog checked and I didn't want any risk of the car failing. Besides I figured at 132K miles I got my money's worth. The original sensors in my Boxster didn't even make it to 100K miles.
Could be your Turbo's engine is in need of a tune up. Kevin's advice to replace the sensors (I'd replace all 4 rather than just the wide band ones) and even the MAF -- mine's original but my engine's stock -- could be just the ticket. Along with plugs of course.
And maybe coils.
Regarding coils: My Turbo engine once in a while -- when left out in the rain, or heavy fog, will misfire upon cold start. Misfire with a CEL, too, not just sound/feel like it is misfiring. It does not misfire at any other time. Next time I have the car in for something I'm having the coils replaced.
#20
I started it this morning. Unfortunately, there is no change from cleaning the throttle body (as I suspected).
I'm starting to wonder if it is just a characteristic to this engine?
Take a look at the video and note the tachometer and when I feel the roughness. Now that I really paid attention, it's not so much a "lumpy" idle, or one that is "missing". I think it's more of a high frequency vibration. It also never has a problem running smooth and strong when I give it some throttle.
Is this normal for these cars? I might need a guy who has a lot of experience with 911 TT to look at it before I drive myself nuts chasing something that's "normal"! LOL
https://www.youtube.com/watch?v=TvuV...ature=youtu.be
I'm starting to wonder if it is just a characteristic to this engine?
Take a look at the video and note the tachometer and when I feel the roughness. Now that I really paid attention, it's not so much a "lumpy" idle, or one that is "missing". I think it's more of a high frequency vibration. It also never has a problem running smooth and strong when I give it some throttle.
Is this normal for these cars? I might need a guy who has a lot of experience with 911 TT to look at it before I drive myself nuts chasing something that's "normal"! LOL
https://www.youtube.com/watch?v=TvuV...ature=youtu.be
#22
Maybe you can have someone video tape from the back of the car when you cold start it.
#23
The sound is fine, you will not hear anything wrong with the sound other than that initial dip for a split second when it is first started. It is visible in the video by watching the tach. I just brushed that off as the car finding it's idle while processing info from the sensors. It's not like it misfires or anything like that. It sounds perfectly smooth, it's just that the car physically shakes/vibrates. it feels like an unbalanced, or very unrefined engine while the issue is happening.
#26
#27
#28
A little more info today.
I noticed that under light to moderate throttle, the engine will sometimes surge when it first switches to 4th gear (Tiptronic). It may actually do a little surge in 3rd right before the gear change too. It did it a few times today during a 30 mile ride. I have definitely felt this in the past, but I ignored it since it is usually VERY slight and the car doesn't miss and it runs strong and it goes away if I give it a little less or more throttle. I was also suspect that it may be a tune issue. For instance, I'm wondering if that is the point where the vario cam kicks in or something like that?
Also, I noticed that if I'm in neutral and hold the throttle at about 1,800 rpm's, I get a good amount of vibration that is very noticeable. I assume that if it's not normal for this car. Another important bit that I forgot. If I'm not completely stopped and I try to put transmission in 1st, I get a pronounced bang when it goes into gear. I'm guessing motor mounts as was suggested (or transmission mount)?
I can't imagine any real problem with a car that has only 19,000 miles.
I noticed that under light to moderate throttle, the engine will sometimes surge when it first switches to 4th gear (Tiptronic). It may actually do a little surge in 3rd right before the gear change too. It did it a few times today during a 30 mile ride. I have definitely felt this in the past, but I ignored it since it is usually VERY slight and the car doesn't miss and it runs strong and it goes away if I give it a little less or more throttle. I was also suspect that it may be a tune issue. For instance, I'm wondering if that is the point where the vario cam kicks in or something like that?
Also, I noticed that if I'm in neutral and hold the throttle at about 1,800 rpm's, I get a good amount of vibration that is very noticeable. I assume that if it's not normal for this car. Another important bit that I forgot. If I'm not completely stopped and I try to put transmission in 1st, I get a pronounced bang when it goes into gear. I'm guessing motor mounts as was suggested (or transmission mount)?
I can't imagine any real problem with a car that has only 19,000 miles.
Last edited by up4speed; 11-25-2015 at 12:32 AM.