erratic revs and stalling

[markbailey]

I have a 1999 V40 T4 which (once warmed up) seems to race and then drop back on the revs. I can be standing in traffic with the hand brake on idling and the revs bang up over two thousand and then back down. Or it can just die. I notice when driving that it can also accelerate without any added pressure on the accelerator peddle and then loose power again with out altering the accelerator peddle. It's not a major increase/decrease but enough to notice.

I've replaced the plugs before to see what staight they were in (black and wet) which does make a difference but to be honest there is something that is causing them to be in this staight over a releatively short time/mileage (year/6000 miles).

I've noticed on another post that I should check the MAF which I have dually done. Doesn't look grubby but cleaned it anyway. No affect so far. Didn't try running the engine without this plugged in though as someone suggest so will try this.

Any other ideas would be greatly appreciated as I have taken this in to the garage ove several years (3!) and all they do is ' nothing shows up on the computer mate'. Of course I must be imagining it - silly me!

PS - also engine light comes on but not always go out after a few trips.

[billofdurham]

Welcome to Matthew's Volvo Site.

This could be a vacuum leak or a faulty Idle Air Control (IAC) valve.

If the check engine light comes on that indicates that a fault code has been set. I suggest you change your garage if they can't find any codes.

Bill.

[markbailey]

Hey thanks for that. I'll give it a go and if I can't find anything I'll punt it up to another garage.