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


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I am in the process of changing the plugs and wideband O2 sensors.  Do I dare say that it's actually FUN?  I may be a little twisted sometimes, LOL

So far everything went smoothly except for the fact that I snapped off the locking clip on one of the coil pack connectors. Be careful of these, they probably get brittle from heat cycling and age.

The worst part is that my production came to a halt until I get a replacement connector.  Thankfully I have a friend that may have an old harness lying around and he may be able to give it to me tomorrow so I don't get delayed a few days waiting for it to come in the mail. 

The interesting part is that EVERY SINGLE plug was loose!  Most were removed with light wrist pressure.  The color of the plugs were all a nice light brown color, but the threads looked like they had a heavy grease on them.  I'm not sure if that was anti-seize used by prior mechanic, or if it was just accumulation from blow by on the loose plugs.  I think that the mistake that the prior mechanic made was to torque the plugs only once.  A lot of people don't realize that the o-ring compresses and the plug will loosen up if it is not re-torqued a few times.   I did them at least 3 times each with a few minutes in between each time. Hopefully that will prevent them from loosening in the future. 

I have a good feeling that the loose plugs may have causes the idle issues that I'm having, and maybe even the sound of a misfire under load.  I'm not having a good feeling about the misfire sound because I'm thinking that it may just be a rattle since there is no code or loss of power or drivability when it does the noise.  In addition, it was very random and I was not always able to duplicate, so I will cross my fingers on this.  I also checked the brackets near the middle plugs just in case they are ready to fail, but they looked brand new (very low miles on the car).

At this point, I'm VERY anxious to road test her to see if there is a difference.

It should be ok to start the car before I install the bumper (after everything else), just to make sure that it is ok, right?  I would hate to have made a simple mistake forgetting something, just to find out after EVERYTHING is all back together!  I'm sure that I did everything correctly, but I'm human so you never know.

Oh, one more question.  Do you guys think that I should disconnect the battery to reset the computer to accept the new plug and O2 sensor parameters, or does it not matter?

Here are some photos of my fun:

 

 

You do not need to reset anything for the car to accept the new plugs and O2 sensors.

 

Nice shop layout, by-the-by. :thumbup:

 

Thanks for the compliments!

Ok great, I didn't feel like having to do all the other initialization stuff, LOL

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I am in the process of changing the plugs and wideband O2 sensors.  Do I dare say that it's actually FUN?  I may be a little twisted sometimes, LOL So far everything went smoothly except for the fact

It's all back together. I have to admit, it is a very easy job. If you are handy and are considering doing the plugs and coils by yourself, don't be afraid. There is nothing hard about it. It definite

I can see you're having fun. I've had fun watching your progress and work. I'm having a similar problem to yours on a stock engine for a 99 996. You are certainly giving me inspiration to do some of t

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I decided to change the coils also. After hearing all the facts and speaking with Kevin at UMW, I decided to replace them since all of the labor is already done. They are the original 996 coils that are bound to eventually fail, so the 997 updated coils sounded like a good idea.
I should have it all together by the end of this week (hopefully). I'm anxious to see the result. I will definitely update with the results.
Keeping fingers crossed thumbup.gif

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On 4/23/2015 at 6:08 AM, alex.j said:

ok. think it was on the swedish porsche forum. a guy had trouble with rough idle. this was helped after the climatcontroll was fixed on pc..

 

Those two systems have no connections to each other - which is why I say that it can not make any difference.

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The only way I could see the climate control affecting the idle is if the compressor is sticking and dragging.  Or when it cycled on, he noticed his idle change slightly, which is normal.

In my case, it was off when having the issues.

I should have it back together later today or tomorrow and I'll report the outcome.

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It's all back together. I have to admit, it is a very easy job. If you are handy and are considering doing the plugs and coils by yourself, don't be afraid. There is nothing hard about it. It definitely takes a long time the first time, but it's not hard.
As far as the results of my work, it's hard to be 100% sure until I get a little more time with it. As of now, I felt like it idles smoother overall, but it still does that whole dip in the RPM's after 3 seconds, then hunts a little for the idle (visible on the tach, not enough to hear anything). Even though it does the same routine that it used to, it feels smoother during that time. I feel like it went from feeling abnormal to something that generally feels normal.
I also haven't heard that rattle sound under engine load that sounded like detonation. I tried giving heavy throttle several times and it just pulls very hard and smooth and doesn't make that noise. I'll have to assume it's fixed unless I hear it again. It also hasn't done that slight surging either.
I'm guessing that the rattling noise was caused by loose spark plugs, and the surging was caused by the leaking v-pipe. Since I did the spark plugs, coils, O2 sensors, MAP sensor, MAF sensor and I still have that dip in RPM's when started cold, I'm going to have to assume that it's a normal characteristic. Especially since it runs great and idles rock solid when warmed up.
If something changes, I will post back, but I will assume that everything is fixed for now.
I want to also thank everyone that chipped in to help me with diagnosing and fixing my car. I appreciate all the time you guys took out to help me!
I also wanted to give a special thanks to Kevin from Ultimate Motorwerks (UMW). He went above and beyond to help me out and his troubleshooting is always spot on, which is truly amazing when the car is thousands of miles away from him!!
Speaking of Kevin at UMW, I have an UMW performance tune on my car and during this whole troubleshooting episode, I went back to stock tune. I can not believe how much slower the car is when stock! The only mod to my car was his tune, and it is a NIGHT and DAY difference in torque and power. I would have never imagined that it would even be possible to make that difference. In all fairness, I don't have experience with turbo cars, and I guess it is probably easier to squeeze power out of a turbo rather than a normally aspirated engine. I'm so impressed with the tune that I'm going to start a new thread letting people know how I feel about it.
 

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On ‎4‎/‎19‎/‎2015 at 0:17 PM, up4speed said:

Thanks for the compliments!

Ok great, I didn't feel like having to do all the other initialization stuff, LOL

I can see you're having fun. I've had fun watching your progress and work. I'm having a similar problem to yours on a stock engine for a 99 996. You are certainly giving me inspiration to do some of the same work! Thanks for the running commentary.

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8 hours ago, monteolsen1 said:

I can see you're having fun. I've had fun watching your progress and work. I'm having a similar problem to yours on a stock engine for a 99 996. You are certainly giving me inspiration to do some of the same work! Thanks for the running commentary.

 

8 hours ago, monteolsen1 said:

 

Thanks again for the kind words.  I just wanted to log in to tell you that I haven't been on the forums lately.  I sold the car recently because I am in the process of selling 2 of my "toys" to buy one better toy, lol.

If you are handy, I wouldn't be afraid to work on these cars.  Some things are very tight in the engine compartment, but other than that, they are easy.  I'm glad I was able to help, that was my whole intent so people can follow my troubleshooting process.

Enjoy your car, and drive it in good health!

Regards,

Chris

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