High revs when idling

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High revs when idling

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Andy

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I posted a while back re the above. The car went into the garage today for checks.

They found that the idle control valve was caked in dirt and so they cleaned that. They also said checks on the ECU found that the Lambda sensor was reporting a fault, and that it would need replacing soon. They couldn't reproduce the error when they had reset the ECU and cleaned and refitted the idle valve.

However, within 2-3 minutes of getting in the car, I managed to reproduce the revs issue by putting the car in neutral and putting my foot on the accelerator to 3500rpm. On taking my foot off, the rev count reduced to 2500, but stayed there for a good 3-4 seconds before returning to 800rpm.

What else could be causing this?

Andy
 
The ECU has to relearn the idle valve plus the behaviour you describe is sorta what it should do normally but not quite at 2500rpm.
 
Thanks Tom

I'll give it a while then. I wonder if a trip from Manchester to London tonight will help it learn...
 
Re: Re: High revs when idling

The idle valve does not move during normal running, only when the engine is cold.
 
Now I'm confused.

I take it that the problems I had when the engine was at running temperature could have been caused by the grime in the valve?

If I experience the same problem now that it has been cleaned, what could be the cause of that?
 
Re: Re: High revs when idling

When you lift the throttle it opens the idle valve wide and then closes it as the revs drop, this stops lots of nasties in the exhaust.

When its cold its adjusting the valve all the time.
 

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