grimkeit

I have a 95 993 that runs great when warm. When it is cold the rpms oscillate slightly til it warms up. Do I need to clean the idle speed valve that sits on top of the metal intake manifold?

ReinerFink

My '95 has done this for as long as I have owned it (since 1998). I even swapped in a new idle stabilizer valve and it didn't help. Since no baby harp seals have died I have acceped this and life has moved on...

-reiner

mongrelcat

Same issue here. It went away over the Summer and now it's back (first year of ownership.) My car also surges in idle at startup when cold, quite high actually, which I doubt can be good for the internals.

Wondering if you two have this accompanying behaviour along with the idle bounce until warm.

ISV was cleaned, didn't make a difference.

PS: This would be a good reason to be sure to drive a car "cold" prior to purchase (the condition of the gearbox is another.)

grimkeit

Car drives and runs awesome, just does this slight oscillation thing (curious) when cold. Maybe this is just the way it is?

Steve Weiner-Rennsport Systems

Make sure your oxysensor(s) are working properly and there are no vacuum leaks in the intake system.

manila3

I assume you have given the car a workout (driven with gusto)?

Stealth 993

Mine does that when cold, goes up to about 1800 rpms, then falls to idle, & hunts up & down for about 1min before it smoothes out.

Every 95 I have seen seams to do this, my 97 does not, except for the starting surge. My ICV is clean, no stored codes, & no leaks that I know of.

Robin 993DX

My first response would be the ISV and the O2 sensor. As the O2 sensors age they react slower.

Cactus

My 95 did this as well until I did the 30K tune up and cleaned the ISV. Starts smoothly everytime now with no loping.

brucec59

I've had this issue. Seems cleaning the ISV fixes it for a while, then it gets dirty again and I clean it again and so on, about 1/year.

Stealth 993

I pulled mine out today to take a look, it had a light film on it, but that's about it. I cleaned it out, along with the TB, & intake.

Guess I'll find out if the car has a smoother cold idle.

ZombiePorsche44

Since I live in the best climate in the US I have only experienced this twice, but still replaced the O2 sensor and cleaned the ISV.

I'll have to hope for one of those cold mornings to see if it does it again, but then again, with global warming being such a problem, I may never know if it worked.................LOL

ZP44

Stealth 993

Maybe I need a new O2, but I cleaned out the ICV, then on start up, it still oscillates about 3-5 times before it finds a smooth idle.

Great, there goes another $100. But when I ran it on the dyno last winter, the A/F was very good.

ofd

Hi,


My new to me 1995 also did the same thing. It has a fabspeed cat bypass and I thought that was causing it, but turns out it was the O2 senser in my case. I also had to put the cats back on for smog testing and not sure I'll put them back on once the car has past. With RSR's and cat delete it's a little raw.
I also will not pass sound check at the tracks I go too.

Cheers,

bluejam

My '95 has done the oscillation at startup since I've owned her the past two years. Only when cold. It only lasts for about 20-30 seconds then smooths out. I figured it's one of those 993 unique quirks, such as the smell, girgling oil, etc.
BTW, I just passed a smog with flying colors so the O2 sensor should be fine, eh?
If it ain't broke, I ain't fixin' it.