Recently changed all plugs and coils; I expected it to get rid of the small amount of variation in idle RPMs I'm seeing, but it stayed about the same. As you can see in the video, it will stay quite steady for a while, then dance around a little bit.


I'm also seeing some knock (knock sums topping out in the 8-11 range normally) across all cylinders when I log a 2nd or 3rd gear pull with my Cobb AP, so wondering if it might be related. Car is on the stock tune with OEM exhaust.

 

Ill look at mine this weekend if I get the car out. I don't think its a big deal, the fluctuation is so small.

 

Yeah, I wouldn't be surprised at all if it were normal. I'm actually hoping it isn't, so I might have more of a lead on why I'm getting this knock in my logs.

 

Nothing to worry about....But if you take the Y-Pipe off and clean the throttle body and plate with MAF cleaner really well, you will find it smooths out the idle. I think over time the build up keeps it from closing well, and makes it search a bit at idle. I do it periodically and it does smooth it out immediately. Good luck.

DC

 

Factory manual for my 2003 Turbo calls out an idle speed of 740 +/- 40 RPMs.

The dash tach ain't the most precise instrument but based on what I observed in the clip and based on what the idle speed call out is for the 996 Turbo I'd hazard a guess the idle variation you are seeing is normal/acceptable.

As for the knock counts...

For my 2003 Turbo I replaced all 4 O2 sensors (this at 132K miles) and the engine ran noticeably better. I had no knowledge of any knock counts but the improvement in how the engine ran was quite impressive.

The O2 sensor replacement was prompted by one sensor tripping the CEL -- it was a heater circuit. Even so the engine ran fine.

The improvement in the engine's performance after the O2 sensor change was kind of a surprise.

Then at around 140K or 145K miles I had the coils and plugs replaced. The coils because they were original and the plugs because the tech was "there". The plugs had around 10K miles to go before they were due to be changed anyway.

Kind of a surprise to me but the engine ran better after the plugs/coils were replaced. Previously I had had the plugs changed -- on miles -- several times and never noticed any change -- good or bad -- in how the engine ran so I attribute the engine's improvement to the new coils. (I think 997 coils were used.)

You might consider if you have not done so replacing all 4 O2 sensors. Even though your engine is stock -- as is mine -- turbo charged engines are harder on O2 sensors than N/A engines.

Also, let me add in an attempt to address a P1128 error code from my 2002 Boxster I replaced the MAF. To my surprise the engine perked up some with the new MAF installed. The old MAF was the original MAF but it had a "break" of around 100K miles when I replaced it thinking it was bad only to find out it wasn't. However, the new MAF was not returnable so I left the new MAF in service until it started acting up and then installed the original MAF which worked just fine. So the original MAF had over 200K miles on it.

I have not yet had any reason to replace the MAF in my Turbo but I'm thinking about it.

My point is you could possibly (maybe) improve the engine's running with a "tune up" replacing some or all of the various items I mentioned above.

However, I doubt you'll steady that tach needle any.

Last but not least if you really want to know if what you are seeing is normal or not normal you need to actually monitor engine RPMs in real time -- I have an OBD2 code reader/data logger which allows me to view RPMs in real time -- then you need to take this info to a Porsche tech and ask him if the idle variation is in or out of spec.

 

Just had a chance to watch mine and it wiggles a bit (now I am new to my car, so who knows if there is anything specific to this one). I did have the car checked by my local (and trusted) shop and they said the car was in great condition, but I am still getting to know her.

But, for what it's worth, my tach looked just like your video.

Ed

 

Does it also wiggle with warmed up engine.?
Switching on/off of Airco compressor can also cause small variations

 

i get that also. no biggie

 

2007 Turbo here and have a very similar fluctuation at idle, under my ownership have always had some slight variation in RPM.

Kevin