idle problem

[dc]

hi guys hoping u can help.got an idleing problem.the car is a august 1990 325isport.the idling is lumpy.the idle screw is missing from the airflow meter but i was told by a bmw technician that if it has a cat it doesnt need it(hmm suspect i know).i have checked the idle control valve and the cold start sensor and they seem to work ok.any ideas would be very welcome.

[Templ8e30]

I'd be tempted to take it to a good fuel injection specialist to have a look at it, could be a number of things.

My 2.7 hates starting in cold weather and has a lumpy idle, all down to the AFM being out of adjustment and bad plug leads. The AFM is now set-up correctly and it made a big difference but still need plug leads

Cheers,

Iain T

[Andy_magic]

The screw missing does sound suspect to me, do you mean the adjustment screw that drops in vertically?

This screw regulates the air that bypasses the AFM when on idle, more air = leaner mixture, with this screw removed the maximum amount of air can bypass the AFM with extra unfiltered air also getting in and bypassing the AFM.

I would look into replacing it!

[Dan318-is]

The screw missing is not suspect. If your car has a catalytic converter the AFM will not have a screw on it.

[Andy_magic]

There should be something in there surely?

[JOSEMI]

ine has no cat and does have a allen screw, which by the way goes up and down by pulling from it...