'94 940 T

I have checked the hoses, found a massive hole and replaced the hose that it was in. Also cleaned the TB. However, I still have trouble idling. 90% of the time it's fine, but every once in a while rpms will drop to 4 - 500 and the engine will obviously shudder a little. After a second, it will return to about 600, where it idles ok. It seems as though the fact that it idels at 600 is a problem in and of itself. Any suggestions? I am fairly confident that there are not any vacuum leaks now that I replaced the one hose. Where do I go next?

Thanks,
John

I have a 940t 2, recently i wa messing about connecting a calibrated guage in place of the turbo guage and left the vacume pipe that comes from the manafold unplugged ..it idled ok for a while (<1 min) then did the sort of thing u descibe..

might be worth checking ALL the vacume pipes inc to the turbo guage...

i presume you have cleaned out flame trap etc etc...

I have a very similar problem on my vectra (dont ask!) andi know that is caused by the equvilant of the flame trap (or rather the brass fitting to the ft on the manafold getting dirty)

just worth a look, oh and my 940 idles at 600 rpm on the money!

Have you done a tuneup recently? Air filter? Fuel filter?
A fuel pressure test may turn up a problem... pretty cheap to do or have done for you.
Good luck.
Rob Bareiss, New London CT

I actually just had the service light come on today. Thought it had had a tune up right before I got it, guess not. So I will have to go through all of that, fuel filter, etc. If that doesn't solve it, I'll be back.


Thanks for the input.

John

Before you go through the all out tune up (fuel filter, etc.) why not clean your fuel system and injectors by running a can of BG-44K through a full tank of gas?

Do an oil/filter change following that, along with the other things you have in mind.

600 RPM is low -- need about 750 base idle. How is the throttle body and its adjustment?

What happens when you sdjust the base idle by pass screw? Typically you'll get almost no change in idle speed when there is a problem somewhere. Or, this screw will be all the way tight and yoou'll still have (usually) too fst an idle.

Check the o-ring on the by pass idle screw and replace it for better performance.
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