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MG MGF Technical - Idling speed

Apologies for posting on this subject because I think it was the subject of a recent thread (which, because I didn't have the problem at the time, I didn't really focus on), which I can't locate in the archive.

My problem is that the idling speed is fine (c.1000 rpm) when the car is first started, but during a run it "races" at 2000-2500 rpm whenever I stop at traffic lights, etc. It settles down with a blip of the throttle, but I'd rather it didn't happen in the first place.

Anyone got any whizzy ideas for fixing this?



Engine managment control does allow for a high rpm level to be held for a few seconds, gradually allowing it to settle to natural idle. This doesn't include rpm above 2000 rpm.

In your case you are suffering a sticky throttle, a problem that is well documented here and in the Rover technical bulletins.

Essentially you first have to locate the area of stiction, throttle pedal area, cable, or most likely the throttle body. Then ensure that wear or obstructions are not the cause, followed by cleaning components. If after this with a correctly adjusted throttle cable the problem persists, then your into a replacement throttle body.

The issue of slight distortion on the plastic throttle bodies is one that has seen a modified body arrive. Newer cars have this as standard, and this is a direct change to older cars.

Another common factor that creates this is to use the non standard clip to hold the pipe from the air filter onto the throttle body. Commonly discarded and replaced by a worm type clip (Jubilee clip) this is able to excert considerable pressure and cause distortion. It is also found when a K&N clamp on filter is fitted for exactly the same reasons.

Throttle bodies have been made from plastic for some years, but originally they were alloy castings. (Which at their time also had their own set of potential problems in poor casting tolerances) However their overall resistance to distortion is far better than the plastic ones and as such many of these have been fitted in place of the plastic ones. I believe that a stock of these was mentioned in a thread 'K series engine parts' or something similar on this and the General BBS.

Roger Parker




This thread was discussed between 11/02/2001 and 12/02/2001

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