Erratic idling v12 xjs

[Tony49]

Hi, hope someone can help me. Could a faulty cold start valve be the cause of erratic idling in my 1987 v12 xjs?

 

[Keoke]

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Hi, hope someone can help me. Could a faulty cold start valve be the cause of erratic idling in my 1987 v12 xjs?

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Not likely unless the valve leaks after shut off.---Fwiw---Keoke

 

[John S Farrington]

Erratic idling is not caused by the cold start valve if it is what I think you call "erratic idling." If the idle speed is constantly too fast it might be the cold start valve but if the idle is cycling rapidly like a lage diesel truck motor might do when mal-adjusted, you have another problem that is an out of adjustment micro switch on the throttle cable. The rapidly cycling idle speed is the result of the micro switch telling the ECU that the car is coasting and the ECU tells the fuel injection to shut off. When the engine speed drops to a point it thinks it is not coasting it turns on again. Increasing the idle speed or changing the micro switch adjustment will stop the problem. Hope this helps.