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E28 520i excessive idle speed

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Hi, having trouble with the idle RPM, here are the symptoms:


Car starts ok, any weather, and will rev at around 800rpm, but within a minute or so the idle will increase up to 1500rpm. Then, whilst driving it's not noticeable, until the clutch is engaged or put into neutral, then the rpm can again increase up to 1500 or so.

This can happen until the temp gauge sits right in the middle, at which point RPM drops to between 800-1000 (think it should be slightly lower, but I can cope with it). Anything less than middle and the RPM is excessive, almost like the auto choke isn't switching off even if the car's been running for a lengthy time.

Trouble is, the temp gauge never reaches right in the middle unless I'm sitting in traffic or similar. Temp gauge generally sits just below middle.


Car is a 1987 520i, any advice is welcome, Cheers.

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Seems to be sorted now.

Took it to an ex-BMW mechanic who's solved it; he said the idle mixture was far too rich, went into the AFM and made adjustments.


Tick over purring beautifully now, so hope this may help anyone having similar issues.





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I’ve had the car for a few months, but apparently two  or three years according to previous owner. I don’t know how the mechanic did it, it’s beyond my capabilities, but it’s worked. 

I’ll have to see how it performs on a cold morning..... but I can wait for that.


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