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Discussion Starter #1
Hi all - I've been having a rough idle problem in my 1997 520i, the car when driving is superb with no problems at all but when it's idling it is very lumpy and occasionally I hear a knocking sound when the rev falls to near stalling (what do you think is actually knocking - its quite loud and hard sounding), I had posted on this before and cn90 give me a great explanation on mass air meters and suggested that I try swapping bits from a mates car which I have done; today we exchanged his known good mass air meter and when I started the engine the car idled great - then we realised we had forgot to connect the hose to the idle control valve, when we did this the car went back to idling rough and if we disconnect it the car again idles great - do you think it's a problem with the idle control valve, I removed it prior to this and cleaned it out although it really didn't seem that dirty. I can also hear it clicking when I shake it.
I note that there is quite a strong suction from the idle control valve pipe.
I have had the codes read and it's all clear just looking an opinion before I go to the hassle of changing the idle control valve as it's a PITA :cry: and I don't think I would go to the effort of swapping the mates over to see if that is indeed the problem, think it would be better just to buy one if I was sure that it was the problem.
Has any one any ideas. :dunno:
Thanks in advance for the help. :thumbup:
 

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Freude am Fahren
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Can you clean the ICV? Have you checked for vacuum leaks?
 

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Discussion Starter #6
Just to update you all I've taken out the ICV to have a look at the part number and have carried out a few tests - I connected the ICV electrical connector only while having the ICV removed (holding it in my hand) and have found that the little valve doesn't seem to move but I can feel a buzzing from the valve body and it sounds as if it's doing something also the knocking noise I have talked about is more frequent - if I disconnect it completely the engine rev drops to a point where it is about to die.
What is the normal behaviour for the ICV?
I have again rechecked for vacuum leaks and have found none.
 

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Normal ICV Function:
- COLD engine, it OPENS so extra air enters engine Intake Manifold
- HOT engine, ICV closes, no extra air.

Swap ICV with your mate's car.
 

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Discussion Starter #8
Hi cn90, can the solenoid become weak and seem to be working but not have enough power to operate and does it close gradually as the engine warms?
Mine doesn't seem to move at all but you can feel a vibration from it and when the connector fell off the engine almost died.
Mate will call back later so will try swapping if he lets me- LOL.
 

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Discussion Starter #10
Hi again took car for a run down the road to see how it idles when warmed up and it's just the same, when reversing it back into the garage the oil light came on and then went out when I give it a rev, I then decided to check the oil level and found it needed about a litre, so I topped it up and now the oil light stays on at idle and goes out when its revved.
Anyone any ideas and do you think it's linked, the oil light didn't come on with the idle problem before until I took it for a run.
 
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