Up and down revs on cold start
Thread Starter
Rennlist Member
Joined: Nov 2006
Posts: 85
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From: nj
Up and down revs on cold start
anyone have any experence with this....'95 993 w/ low miles.
When car is started and engine is cold, revs will fluctuate up and down for maybe 10 seconds or so then go back to normal. Want to nip it in the bud so it doesn't lead to a bigger problem.
Thanks!
When car is started and engine is cold, revs will fluctuate up and down for maybe 10 seconds or so then go back to normal. Want to nip it in the bud so it doesn't lead to a bigger problem.
Thanks!
Rennlist Member
Joined: Aug 2002
Posts: 703
Likes: 1
From: indy- ft.wayne
I had the same problem in a 3.0 car and replaced the cold start valve, but have not experienced it with my 993. have you tried a search of the forum yet.
My Grand National does it pretty regularly which they are known for, but that is the IAC.
My Grand National does it pretty regularly which they are known for, but that is the IAC.
Burning Brakes
Joined: Nov 2004
Posts: 1,121
Likes: 2
From: Watkins Glen, NY
My 95 with 56K miles does it too. The colder the day the longer it does it. Particularly this week after sitting in the lot during the day with a wind chill of -15. But usually no more than 5-10 seconds. I'm not particularly worried about it as the car is running great.
Rennlist Member
Joined: Nov 2006
Posts: 2,192
Likes: 111
Originally Posted by briefescape
My 95 993 with high miles does exactly the same . I am not worried about it though it is the beast just waking up 
Same here. 95 993 with 64k and she does the same thing....
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Burning Brakes
Joined: Nov 2004
Posts: 1,121
Likes: 2
From: Watkins Glen, NY
Looks like a good project for this weekend. No sense in leaving it alone now that I know how easy it is to fix. Thanks guys. Here is a good thread on the ISV. A few posts down there are a couple helpful DIY links to p-car.com.
https://rennlist.com/forums/showthre...abalizer+valve
https://rennlist.com/forums/showthre...abalizer+valve
Three Wheelin'
Joined: Dec 2004
Posts: 1,779
Likes: 1
From: Halifax, Nova Scotia , Canada
Lets see if cleaning the ISV does anything.
The DME has a fuel enrichment map that is head temperature driven . A combination of top tolerance fuel pressure and lowest tolerance head temperature sensor will lead to a slightly overrich mixture and then slight hunting. All motors hunt with too much fuel.
Soon as the head warms up a little, its all over .
I seem to remember that Porsche say to fire up and drive away . First set of lights everything will be fine .
Geoff
The DME has a fuel enrichment map that is head temperature driven . A combination of top tolerance fuel pressure and lowest tolerance head temperature sensor will lead to a slightly overrich mixture and then slight hunting. All motors hunt with too much fuel.
Soon as the head warms up a little, its all over .
I seem to remember that Porsche say to fire up and drive away . First set of lights everything will be fine .
Geoff