fokker

Posted: Thu Aug 19, 2004 6:43 pm Post subject: coldstart issue on 951!

--------------------------------------------------------------------------------

My 944 turbo -89 has started to behave strange during coldstart.
The rpm first drops down low and it hesitates and then it compensates up to 1300-1400rpm. Then it slowly goes down to normal 8-900rpm. The hole progress is just within 10sec. So after that it works fine again, and only at cold start.

Could it be the TPS Throttle position switch?

I had boost boost problems some weeks ago and it was solved with disconnecting the battery. The idle thing started to go bad at the same time that the boost problem came. But only the boost problem was fixed with the disconnecting the battery. (the boost problem was that i just had 1,1 boost instead of 1,8-1,9)

Please any comments!!

Thanks
´Dave

fokker

anyone?

daniel951

my guess would be the idle stabilzer? My car did that when i had a 87 944 NA but never fixed it because i sold it before i start researching the problem

hosrom_951

During cold start ups, the ISV (Idle Stability Valve) switches on. It USUALLY goes bad when you get idle surges from high-low-high-low etc.

The TPS MAY be the problem; However, you say that this happens ONLY when it is cold? thus the TPS is 90% ruled out, unless the problem continues even when the engine is warmed up.

Check ALL vacuum lines (small and big ones, especially the ones going to the ISV, also check for tightness).

Here is a picture of the vacuum diagram for the 944 turbo that has been circulated a number of times:



If the vacuum lines are fine, try bypassing the ISV by jumping a wire between ports B and C as show in the diagram on the diagnostics plug (however, this should be done when the engine is warm)



Here is a link on how to check and adjust the TPS (which i doubt would be the problem)

http://www.clarks-garage.com/shop-manual/fuel-06.htm

daniel951

i think u can run the car without the idle stablizer and see if that is the problem

hosrom_951

Yes you can, but the ISV was intended for cold startups and when the a/c is turned on.

Might not get smooth running, but yes, that is another way of checking.

daniel951

just curious do u still have your Cycling valve? I don't know if this can play a role in such thing but it could also cause problem with boost

hosrom_951

Daniel: Even if the CV is not there, no problem AS LONG HAS HE HAS A RELIABOOST,ACCUBOOST or something similar going from the IC banjo DIRECTLY to the wastegate.....

daniel951

that is what i thought so the CV is a stock boost controller another words. i am trying to think what the problem can be with it doing that on cold starts. I remember mine used to do that only one its first start of the day or if i leave it alone for a 4+hours and start it again.