1990 300CE Idle erratic when warm

pugboy

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I am scratching my head with this one, the old girl starts and runs great for about ten mins, perfect idle, then once it warms up, I assume when it switches to 'warm' fueling it suddenly starts erratic idling, up to about 1500 for a while, and if the throttle is blipped it'll rev up and down for a while on it's own before stabilising again at 1500ish, or sometimes dropping down to stalling. Smells like it's running rich. could it be a sensor of some sort?

Any comments/suggestions would be appreciated.

Cheers

Chris
 
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pugboy

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..forgot to mention it's the 12 valve M103 engine
 

television

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If it is over fueling you could try grounding the air and water temp sensors, just short the terminal down to the engine, try it with the engine running
 
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pugboy

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Cheers for that Malcolm, there are a few different sensors; some on the side of the engine and then at least one near the rear of the engine nearer to the bulkhead (a larger diameter plug with several terminals). Not sure which sensor is which. I'm guessing one relates to the fan and then at least one to fuelling. I'm a bit of a layman so not sure which to go for first.

SOrry for being a thicko!! :D
 

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Will come back to it later :D:D
 

Seeker_UK

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Do the 12 valves have an idle control valve?

If so, worth hoyking it out and spraying it with carb cleaner.
 

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It will have a rotary idle valve
 
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pugboy

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I've stripped the idle contol valve and run through with carb cleaner and sprayed through with wd40 then rebuilt. Whatever it is only happens when warm so I assume it's to do with something controling fueling. Which is most likely culprit if sensor?

I see malcolm has a link to a good parts site but not sure which sensor to try.

Cheers

Chris
 
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