yoni_d

Hi All,

I have a 1980 euro model - manual gear, and I have a strange idle problem.
Usually after I start my car and it heats up, the idle drops to around 600-700rpm. However, if I slightly touch the gas pedal and by slightly I mean that I rev until 1000-1100rpm, the idle is then at 900. After some time is drops again to 600rpm and if I dont perform that trick, it will stall (after some time).
Strangely, this problem is less severe after driving a little, turning off the engine and starting it again. The idle then holds at 900rpm but also after some time it gradually goes down too 600rpm and after some time stall.

I am really puzzled here....if there was a vacuum leak I assume that my trick of raving to 1000rpm wouldnt worked - or am I wrong?
Any ideas?
Thanks!

Guy

Hanging idle is usually indicative of a lean condition as you alluded. I would be curious to see what your pressure readings are. My guess is that crud in the fuel system is spiking your fuel pressures and leaning you out a bit

yoni_d

Thanks - I cant check the pressure at the moment but based on what you are saying, if I will slightly close the CO bolt (in order to make the fuel / air ratio richer) the problem should be solved. Am I correct?

Guy

In theory yes but note how much you adjust so you can have a baseline to correct the adjustment once the underlying issue is corrected. Also, keep in mind that A/F is only being adjusted for IDLE conditions. Once the car is accelerating, the mixture is determined largely by the control pressures so you will still be running lean under acceleration.

Petza914

What's your idle when the car is cold and first started - is it elevated at around 1,500 RPM like it should be or does it always start up at 900 or 1,000 RPM. If the latter, I'd say your Auxiliary Air Valve isn't working properly. It's aperture is open when cold and closes as it warms up from the 12v it receives via the plug. If yours is never opening things may be misadjusted to account for that.

You could also just rotate the idle bypass screw a little bit to raise the idle. Think I have my K-Jet car set to idle around 1,000 RPM when warm and it's rock steady there. I would also check your throttle cable linkage and butterfly to make sure it's not hanging and creating that inconsistency.

yoni_d

Thanks - I will do that test and try to mark the original location.

When I start the car it starts at around 800 and then increases to ~1200 but quickly drops to around 600 - 900rpm (depends if I do my trick...). I checked the Auxiliary Air Valve and it does open.
Increasing the idle doesnt work. No matter what I do it will "loose" 200rpm after some time so unless I set it to 1200rpm (which I dont want) I cant really do that.
Maybe the problem is indeed with the throttle cable linkage...never thought of that. Thanks!

Guy

Control pressures will tell the story at this point. I know it's not in your immediate future according to your post but therein lies the answer.

Any time I have had weird idle issues. Always comes back to the WUR

yoni_d

Thank you! Once I will be able to check the fuel pressure, I will do it! I know that the WUR can play tricks on us