Hi

I have an Volvo 765 (1989) an i have a problem with the engine. When I am driving sometimes the Rpm goes automaticly to 2500/3000 rpm.
Does anybody has an idee what this can be

Thanks

Check good for vaccum leaks.If no leaks check the idle motor.

Thank you for your advice, I will look to it but i still have a question when it is an vacuum problem isn't it strange that it not always some day i do not have any problem at all. And my other question what do you mean by the idle motor and where is it. I have a langue problem because i am dutch.

Thanks

It could also be a bad brake booster.When you hit the brakes then diaphram moves and sometimes it will leak and others it won't.


The idle motor is under the throttle body follow a hose from the induction hose to the idle motor.It looks like a cylinder with 2 hoses going to it.