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up4speed

2001 996 TT idles rough for a few seconds when started cold.

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I searched all over the Internet for my problem, but the solutions seem to be all over the place. I also didn't find the exact symptoms as my car. Hopefully someone knows what the problem is, or someone can help me with step by step troubleshooting.

I noticed that when my car is started cold for the first time of the day, it idles rough. It won't stall, it just feels lumpy. This will last for a few seconds, or until I rev the engine a few times. Once it smoothens out, it stays smooth and runs strong. The check engine light did not come on and the car will start right up without hesitation also.

The spark plugs and coils were changed within a few thousand miles and I recently changed the air filter and fuel filter. I also cleaned the MAF/MAP sensors.

I have an obd2 reader....where do I start?

I was thinking of starting with hooking up the obd2 on a cold engine to see if the readings on all the temp sensors make sense.

Please help!

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Is the car stock? What coil packs did you use (upgraded 997's)?  Were the plugs gapped correctly?  TB should be cleaned.

Edited by wross996TT

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Have you cleaned the throttle body?

If you have not use only throttle body cleaner and do not spray the MAF.

 

I haven't cleaned the throttle body, I will try it as soon as I get a chance.

Is the car stock? What coil packs did you use (upgraded 997's)?  Were the plugs gapped correctly?  TB should be cleaned.

I purchased the car almost a year ago.  It is pretty much stock.  The only thing that I know it has is a tune.  The coil packs and spark plugs were replaced shortly before I bought it, so I'm not sure if they were done correctly, or what part #'s they used.

I will try the throttle body cleaning.  On another forum, they recommended that I change the MAF also.  Is there a way that I can check it so I don't randomly throw parts at the car?

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A little additional info.  I just hooked up my OBD2 reader with key on, engine off on a cold engine (approx. 50 deg).  I attached the photos of the reader showing all the pages of readings for the live data (there were no pending codes). 

I then started the car and it was rough again (it's 100% consistent when cold). It idled at 1200 rpm, and it varied by about 100 RPM.  I also was able to smell a rich mixture from the exhaust.

I hope this info helps a little.

post-17066-0-83213500-1427340428_thumb.j

post-17066-0-00415100-1427340439_thumb.j

post-17066-0-50871000-1427340450_thumb.j

post-17066-0-26878300-1427340459_thumb.j

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Another possibility is the tune...anyway to flash back to stock?  Any idea who's tune it is? TMK, that reader is not capable of reading the Porsche codes as precisely as needed.  Try Durametric (unless you can get a hold of a PST2 or PIWIS)

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Another possibility is the tune...anyway to flash back to stock?  Any idea who's tune it is? TMK, that reader is not capable of reading the Porsche codes as precisely as needed.  Try Durametric (unless you can get a hold of a PST2 or PIWIS)

The tune is from Ultimate Motorwerks according to the paperwork with the car.

I don't think it's the tune because I had the car for less than a year, and it just starting doing this right before the winter.  Then again, maybe it only occurs as the weather gets colder.

 

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 had just cleaned it, but I won't know if it improved unless I start it cold tomorrow morning.

I'll report back tomorrow.

Edited by up4speed

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I would contact Kevin.  He is very helpful and stands behind his work.  It might just be you need him to adjust the idle rpm...

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I would contact Kevin.  He is very helpful and stands behind his work.  It might just be you need him to adjust the idle rpm...

Kevin saw my post on the other forum where I asked the same question (he responded).  He didn't know that my car had a tune at that point. 

I don't think that it's an idle rpm issue because the car is idling at about 1,200 rpm's when it is cold, it just runs rough, it doesn't threaten to stall or even dip low in the rpm's.  The idle varies 100 rpm at most while it's running rough. The car smoothens out after a short while, and once it's warmed up, the idle comes down to about 800 rpm.

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https://www.youtube.com/watch?v=TvuVzOdvNNE&feature=youtu.be

 

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

 

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https://www.youtube.com/watch?v=TvuVzOdvNNE&feature=youtu.be

 

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

 

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I heard nothing unusual...of course I could not feel it...mine does not idle at that RPM.  I don't think anything is wrong.

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https://www.youtube.com/watch?v=TvuVzOdvNNE&feature=youtu.be

 

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

 

All of the turbo cars have a bit of a lumpy idle when compared to the normally aspirated cars, but many times idle vagaries can be traced to failing motor mounts.

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Very high idle rpm in fact!!! I wonder if , having such a high idle rpm, if you are not at the edge of the cam advance…. But I am also wondering if all this is not cause by a leak of a sense line…Difficult to troubleshoot….

post-29683-0-09581200-1427472509_thumb.p

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I heard nothing unusual...of course I could not feel it...mine does not idle at that RPM.  I don't think anything is wrong.

There is no problem with the way it runs, or the sound. Everything I'm complaining about has to do with the feel.  It just feels like a rough or unrefined engine for a little while after a cold start.  The RPM's start that high (~1,200) but after warming a little, they settle down to 800 rpm.  There are no drivability issues.

 

 

https://www.youtube.com/watch?v=TvuVzOdvNNE&feature=youtu.be

 

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

 

All of the turbo cars have a bit of a lumpy idle when compared to the normally aspirated cars, but many times idle vagaries can be traced to failing motor mounts.

 

If it was a failing motor mount, wouldn't it vibrate all the time?  I guess it does feel the same as a bad mount, but it only does it for a short time and only on a cold start.

 

Very high idle rpm in fact!!! I wonder if , having such a high idle rpm, if you are not at the edge of the cam advance…. But I am also wondering if all this is not cause by a leak of a sense line…Difficult to troubleshoot….

The idle doesn't stay there.  That is only when it is initially started cold.  It settles in at 800 rpm, which I believe is perfectly normal.

I agree, it seems to be a very difficult troubleshoot, I'm usually very good at troubleshooting, but this has me stumped!

My best bet is probably to go to a mechanic that knows these cars very well so they can check it out.  For all I know, it may even be a normal characteristic of these engines.

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I heard nothing unusual...of course I could not feel it...mine does not idle at that RPM.  I don't think anything is wrong.

There is no problem with the way it runs, or the sound. Everything I'm complaining about has to do with the feel.  It just feels like a rough or unrefined engine for a little while after a cold start.  The RPM's start that high (~1,200) but after warming a little, they settle down to 800 rpm.  There are no drivability issues.

 

 

https://www.youtube.com/watch?v=TvuVzOdvNNE&feature=youtu.be

 

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

 

All of the turbo cars have a bit of a lumpy idle when compared to the normally aspirated cars, but many times idle vagaries can be traced to failing motor mounts.

 

If it was a failing motor mount, wouldn't it vibrate all the time?  I guess it does feel the same as a bad mount, but it only does it for a short time and only on a cold start.

 

Very high idle rpm in fact!!! I wonder if , having such a high idle rpm, if you are not at the edge of the cam advance…. But I am also wondering if all this is not cause by a leak of a sense line…Difficult to troubleshoot….

The idle doesn't stay there.  That is only when it is initially started cold.  It settles in at 800 rpm, which I believe is perfectly normal.

I agree, it seems to be a very difficult troubleshoot, I'm usually very good at troubleshooting, but this has me stumped!

My best bet is probably to go to a mechanic that knows these cars very well so they can check it out.  For all I know, it may even be a normal characteristic of these engines.

 

 

Bad engine or transmission mounts usually show up only under certain circumstances, which is why they often get overlooked.  When the engine is "loping" at idle, it is really trying to move around quite a bit, so a weak mount would make if feel even worse than it really is.

 

I also would expect the car to normally run at higher RPM's than the regular idle speeds on a cold start.

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I heard nothing unusual...of course I could not feel it...mine does not idle at that RPM.  I don't think anything is wrong.

There is no problem with the way it runs, or the sound. Everything I'm complaining about has to do with the feel.  It just feels like a rough or unrefined engine for a little while after a cold start.  The RPM's start that high (~1,200) but after warming a little, they settle down to 800 rpm.  There are no drivability issues.

 

 

https://www.youtube.com/watch?v=TvuVzOdvNNE&feature=youtu.be

 

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

 

All of the turbo cars have a bit of a lumpy idle when compared to the normally aspirated cars, but many times idle vagaries can be traced to failing motor mounts.

 

If it was a failing motor mount, wouldn't it vibrate all the time?  I guess it does feel the same as a bad mount, but it only does it for a short time and only on a cold start.

 

Very high idle rpm in fact!!! I wonder if , having such a high idle rpm, if you are not at the edge of the cam advance…. But I am also wondering if all this is not cause by a leak of a sense line…Difficult to troubleshoot….

The idle doesn't stay there.  That is only when it is initially started cold.  It settles in at 800 rpm, which I believe is perfectly normal.

I agree, it seems to be a very difficult troubleshoot, I'm usually very good at troubleshooting, but this has me stumped!

My best bet is probably to go to a mechanic that knows these cars very well so they can check it out.  For all I know, it may even be a normal characteristic of these engines.

 

 

Bad engine or transmission mounts usually show up only under certain circumstances, which is why they often get overlooked.  When the engine is "loping" at idle, it is really trying to move around quite a bit, so a weak mount would make if feel even worse than it really is.

 

I also would expect the car to normally run at higher RPM's than the regular idle speeds on a cold start.

 

I agree, I don't think the high idle is abnormal.   Is there an easy way to check the engine mounts on these cars?

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Usually the rubber in the mount is either torn or has sections totally missing.  This happens to be a transmission mount insert, but it will give you the basic idea:

 

bushing3.jpg

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Usually the rubber in the mount is either torn or has sections totally missing.  This happens to be a transmission mount insert, but it will give you the basic idea:

 

bushing3.jpg

I've seen failed mounts, but I was wondering if there is an easy way to see, or test them on this actual car.  I didn't look at them carefully.  Maybe I can just grab the engine and shake it to see if it moves?

If I am correct, they should be very easy to change on this car, right?  I have a lift in my garage, so that should make it even easier.  I'm not near the car now, so I can't look now.

It's very possible that the mounts are bad because I always felt that the car idled a little rougher than I thought it should.  I was just under the impression that it was normal because everyone says that they are a little rougher than the Boxsters and that's what I compared it to.  I had a 2001 Boxster S

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Usually the rubber in the mount is either torn or has sections totally missing.  This happens to be a transmission mount insert, but it will give you the basic idea:

 

bushing3.jpg

I've seen failed mounts, but I was wondering if there is an easy way to see, or test them on this actual car.  I didn't look at them carefully.  Maybe I can just grab the engine and shake it to see if it moves?

If I am correct, they should be very easy to change on this car, right?  I have a lift in my garage, so that should make it even easier.  I'm not near the car now, so I can't look now.

It's very possible that the mounts are bad because I always felt that the car idled a little rougher than I thought it should.  I was just under the impression that it was normal because everyone says that they are a little rougher than the Boxsters and that's what I compared it to.  I had a 2001 Boxster S

 

 

You will need to support the engine while swapping them out, and may find that access from above may be restricted by some stuff that is removable, but they are not overly hard to change out:

 

109-00_996_1997-04.gif

 

There are also multiple aftermarket vendors of "improved" mounts that use replacement materials like urethane to improve their strength, but also tend to impart higher vibration in the process.

 

Because the turbo engine is a race derived unit, it shakes a bit more than the more pedestrian M96/97 street engines.  If the mounts are really bad, you can usually see the engine move when someone revs it.

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Thanks for all info!

That write up is great! It seems like a very easy job with a lift. Now I just have to look more carefully at it to determine if the mounts are actually bad. I'm having trouble believing that they are bad since the car has only 19,000 miles on it. But I gues the rubber could have deteriorated due to age for sure.

I will definitely keep you guys posted on what I decide to do. It's not too bad of a vibration so I want to make sure it's not a normal characteristic of a 2001 996tt before I start spending money on it.

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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. It's enough where the tiptronic buttons on the wheel make a vibrating noise! 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'm starting to wonder if I have more than one problem? It's amazing how I'm starting to remember stuff that I ignored along the way. Part of it is that I only put about 1,500 miles on it since I bought it, so I don't have a lot of experience with it.

Edited by up4speed

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I just freaked out!
Based on my above post and more research that I've done, I decided to replace the engine and transmission mounts. I figured that since the idle is rough and there is a spot at 1,800rpm that oscillates and vibrates excessively, that I would replace both mounts with hopes to fix the problem. I figured that even if I was wrong and they are fine, I bought myself another 14 years before it needs them again. Then I decided that since I went this far, I might as well order a new MAF sensor too! Hopefully it fixes the surging, but if it doesn't, once again I buy myself some time with a consumable item, and possibly even improve my gas mileage a little.
Even if these items don't fix anything, it will help the mechanic a little with troubleshooting.
I know I'm a little nuts, but perfection is a minimum standard when it comes to my cars!

I ordered everything just now, I will definitely give updates after the work is done so I can hopefully help others if they have similar issues in the future.

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