Porsche_993

I have a 1995 Porsche 993 Carrera Cabrio with 95k.
During cold starts there is irregular reving.
It revs from 1000-2000 and then back to 1000 for about a minute.
It cycles every 3 seconds.

This stops after about a minute.

Has anyone else experienced this problem?

Appreciate your help.

Porsche_993

Zingari

Have you tried cleaning out the ISV the butterfly valve might be clogged up. On a pre-varioram it's a piece of cake to take it off, soak the valve end in thinners etc, dry off and then replace.

Dplus

My car has the exact same symptom, '95 c2 cab, 34000 mi.

Where is the ISV located?

Thanks,

Darell

PNogC2S

Check out the link at pcarworkshop -- http://www.pcarworkshop.com/index.ph...-_ISV_Cleaning

flatsixforme

It's the metal cylinder at the very top of the engine connected to that "J" aluminum tube in this picture. It is directly in the center of the engine and just under the sound pad

Dplus

Thanks Pnog C2S,

Totally worth my $17.00 membership fee!!!

D.

Stealth 993

Can't believe "Porsche 993" user name wasn't taken.

When the car is stone cold, it will rev up & down, then settle on a fast idle. But 2000 is a little on the high side.

First, clean out the ICV, & make sure all maintenance is up to date.
Then check for any vacuum leaks, the little black vacuum hoses love to pop out, they mostly hide under the intake plenum.

shadow993

If that isn't it....might be the head temp sensor

P-daddy

Oh damn. I just did this DIY several days ago and should have taken some pics for the pre-varioram folks. It's slightly different than the DIY Robin wrote up. The ISV is rotated 180 deg compared to Vram engines.

Stealth 993

Having done both, it's easier on the 95.

It's the big round thing on top of the intake with the corrugated hose going to it.

SkiDan

Good question. I have the same issue.

P-daddy

Thanks Mike for the pic. You are correct. Very easy job on the 95. I loosened the back clamp first, then I removed the ISV with that big giant hose attached....much easier than releasing the big hose from the valve.

Cactus

Is it possible that the ISV can go bad? i have some issues with high revs at startup and then when restarting a warmed engine the revs sometimes go high then come down slowly.