Idle not dropping when I clutch

[JeTexas]

I checked my tire size. I do have 265/40R18 tires in the rear, and the manual does call for 265/35ZR18.

I turned the traction control off, and the hanging idle is completely gone.

The only thing that puzzles me is that I had those tires on there at least six months before I noticed the issue. I wonder if this is really a tire size problem or some other malfunction in my ABS/Traction control unit.

But yes, turning off traction control made the problem go away.

[jamesgood72]

Wow, well there you go! So the problem is finally solved (other than that it didn't seem to be noticed immediately after the new wheels went on)?

-James.

[JeTexas]

Wow, well there you go! So the problem is finally solved (other than that it didn't seem to be noticed immediately after the new wheels went on)?

-James.

I went back over my records. Last spring not long after I got the new tires I started having high idle issues, which were tracked back to a vacuum leak from a broken oil filler tube. Just a couple weeks later I noticed the hanging idle. It's an intermittent problem, and I think it must have been originally masked by the vacuum leak.

The kicker is that I just bought new rear tires in February. If I'd only known then.

It feels really good to finally have a solution though.

[jose]

I just simply can't believe all you went thru. tire size? wow. I think psm light should got on immediately after those tire size.

Porsche dealer saying... no it's the DME...lol

PIWIS, PTS2 saying no problems

the rest of suggestions were locally acceptable :lol:

[JeTexas]

Just an update. I'd been driving with the traction control off for the past year to remedy the idle issue. I was very paranoid that when I finally bought new tires, the issue would remain and that the problem would be in my electronics somewhere.

I bought new tires last weekend and got the correct 265/35ZR18 rears. The issue is completely gone, and everything is working perfectly.

[hardtailer]

On 4/16/2009 at 2:14 AM, 1999Porsche911 said:

The 99 C2 TC has a cable controlled throttle and the TC does not work in the way you described. I don't see how this would effect the idle.

 

Raising this topic as I had the same symptoms.

The TC actually does work as described when it tries to reduce engine braking torque.

See here for more info

switching off the TC or changing the rear tyres to the right size (285/30R18 or 295/30R18) stopped this behaviour.