944 Turbo - replacing ‘idle speed adjuster’?

[pse_SC]

I’ve just bought a lovely ’86 944 Turbo and have a question for you all...

When returning to tickover, the idle speed drops right down low, then regains itself to ‘normal’ (850-ish rpm), which is a bit of a pain, particularly in traffic. Drives lovely otherwise, smooth, no jerking etc in traffic and all good as it should on boost etc, on open road. Have checked all vacuum hoses etc and seem to be OK.

On my previous 924S (similar engine, essentially), I replaced the idle speed adjuster (valve) and this cured the same issue I’d had with it.
So I’m going to replace the ISV on this car, hopefully to effect a cure - any thoughts anyone, please?

 

[PSH]

these are very expensive items.. I would try cleaning the valve first, try disconnecting the middle vac hose on the inlet manifold and spraying some carb cleaner down it first. It's easy to tell if the valve is working, get someone to turn the ignition on (not crank) while you listen, if working you'll hear it vibrating.

Pete

 

[pse_SC]

Thanks Pete, so you presumably think this is a possible culprit for the ailment?
I’ll try what you suggest first - worth a go...[]

 

[PhilKent]

I assume when you say ISA (idle speed adjuster) you mean the ICV Idle control valve (which is located under the inlet manifold between cylinders 2&3)? If so then yes it's the likely culprit and is a bit of a pain to remove to clean etc, but can be done or can be tested in-situ.

 

[PSH]

As Phil confirmed, yes I do suspect this to be the culprit, it would be my first port of call..although I forgot to mention it in my recent 'Trial and tribulations' thread, I did have an issue of the revs dropping off on closing the throttle, cutting out altogether if doing fast throttle shutoffs...all cured once I cleaned the valve using the method I said in my last post

cheers

Pete

 

[blade7]

The ICV is prone to leaks too. I think people have sealed them with JB Weld.

 

[PSH]

The ICV is prone to leaks too. I think people have sealed them with JB Weld.

there's a video on youtube of someone who's replaced the rubber 'O' ring which literally fell apart when taken out, just like my throttle rubber seals did when taken apart. As with everything rubber on our cars especially under the inlet manifold where these parts live, it's very hostile, any parts with original rubber components are history by now, same goes for the loom and the vac hoses under there....

 

[blade7]

The ICV is prone to leaks too. I think people have sealed them with JB Weld.

there's a video on youtube of someone who's replaced the rubber 'O' ring which literally fell apart when taken out, just like my throttle rubber seals did when taken apart. As with everything rubber on our cars especially under the inlet manifold where these parts live, it's very hostile, any parts with original rubber components are history by now, same goes for the loom and the vac hoses under there....

Yes I've seen that but there is some metal bending to get at the seal, and then finding the right size/heat resisting seal.

 

[Paul 290T]

Might be worth checking the positioning of the TPS. Mine was marginal, meaning that sometimes it detected closed throttle and some times it did not. i adjusted the TPS position by a tiny amount so that it always correctly detected when the throttle was closed. Cured my erratic idle problem.

 

[944Scott]

When chasing vac leaks I did find the body of my icv to be leaking and more recently a weak idle. after following the clarks link below the car idles so much better.

http://www.clarks-garage.com/shop-manual/fuel-08.htm

 

[pse_SC]

Well, thanks for all your welcome replies and thoughts. All very useful info to help sort...
No wonder the 944 forum is one of the busiest in the Club []

TPS = Throttle Position Sensor?... will look at Clarks Garage []