Hello everyone!

My 944s2 89 has a problem with idle: warm engine is allways working unstable. It fluctuated about 500-1000rpm.
Does anybody have the same problem?

Thanks in advance.

 

Bad idle = vacuum leaks, bad isv and hoses

Have you replaced your vacuum lines since owning the car? That would be the first place I would go to. Make sure your all of your clamps on the ISV are tight, and the hoses are good on all vacuum lines.

 

Agree, hunt for vaccuum leaks.
Two of my idle instability experiences that may also help:
1) If the car sometimes nearly stalls when you let up on the throttle, that would be another sign of a sticky ISV. Sticky ISV leads to lag in the feedback in the idle control loop, leading to oscillation, and also system can't respond fast enough to make a smooth transition into idle.
2)Idle will also bounce repeatedly if the TPS is not working, though in my case it bounced much higher and fell much lower.

 

Yes - I was going to suggest TPS may be acting up. But you should check all of the vacuum lines first. Good luck. Glad you got the car to run. The rest should be a lot easier to diagnose.

 

I had this issue so over the winter I replaced all the vacuum lines, the inlet manifold gasket and cleaned the ISV. Idle is now steady so it seems to have worked - unfortunately I couldn't tell you which of the above fixed the issue.

 

Thank you! Car is good now!

 

Thanks everybody for answers!
In my case the reason of unstability idle is wrong position of TPS - I have turn it for 5mm, and the engine started to work stable!

 

Awesome!