Idling problem, info on ICV needed.

[TheKoose]

Hey chaps

Cars running beautifully now, except once in a while it hunts at idle between 500 and 1500 revs. If i disconnect the idle control valve it stops and idles perfectly albeit at 1200rpm. Ive replaced the whole ignition system(just for service reasons) all fluids , the afm to throttle boot, cleaned and reset the throttle position sensor and AFM. Also cleaned out the throttle itself. Can i assume that from this its a funny idle valve?

Mark

[fowler]

sounds like a vacum leak to me

[TheKoose]

All seals etc have been inspected...about 50 times!!

[kam-325i]

Which engine....?

[TheKoose]

Oops how stupid of me. M20 325i 1987

[march109]

spray carb cleaner or similar onto the intake manifold gasket area and look for bubbles.

[TheKoose]

So the fact it idles perfect when you disconnect the ICV has nothing to do with it?

[kam-325i]

So the fact it idles perfect when you disconnect the ICV has nothing to do with it?

Not Yet..........any M20 will idle at 1200rpm with the ICV disconnected, good or not....

With the ICV connected, and idling badly, take of the oil filler cap and see what happends.

[TheKoose]

Tried spraying carb cleaneraround the intake parts, again nothing, no leaks. Took it for a drive and its now all good stranegly. If it does start again ill try the oil cap thing. It has very good compression.

[kam-325i]

The Oil Cap thingy........

When the engine is on idle, take off the oil filler cap. If the revs drop and it starts to hunt a bit, then this is a good sign that there are no air/vacum leaks in the intake system. If nothing happens, then this is a sign that there is an air leak somewhere......

[TheKoose]

cool, thanks alot

[DaveD]

have you had the throttle body off,,did you replace the gasket(37p) and I assume you cleaned the icv out with carb cleaner

[TheKoose]

Hi Dave,

I did clean the icv with brake and clutch cleaner, i didnt replace the throttle gasket though, it looked ok

[DaveD]

i didn't but had too ..as you said it looked ok...but for what it costs and it only takes 10 minutes

[TheKoose]

The Oil Cap thingy........

When the engine is on idle, take off the oil filler cap. If the revs drop and it starts to hunt a bit, then this is a good sign that there are no air/vacum leaks in the intake system. If nothing happens, then this is a sign that there is an air leak somewhere......

Oddly, when it was idling funny last night i removed the cap and it idled perfect, in the same way that when i disconnect the ICV it idles perfect.

[Martinaston]

If you allow more air in by removing the cap and it then behaves it sounds like its running rich, what do the spark plugs look like ?

[TheKoose]

Just in case it helps anyone, it turned out to be the airflow meter.