00 V70R idling problem when hot

Post by **sanfelice** » 13 Aug 2015, 15:02

The problem ONLY happens while car is hot, and runs fine (great, even) when it is cold.

The car seems to run very rich at idle, as I can see smoke at times from the exhaust while idling and hard acceleration.

The major vacuum leaks have been plugged, checked out with a smoke machine by a volvo mechanic, so I don't suspect that is too much of an issue, although it may still be possible. The MAF was changed with two other used MAFs, still the same issue. The Temp Sensor in the bock was changed, better throttle response but no change to the idle problem. The plugs are newer, the coils were all replaced with Bosch 5k miles ago. The O2 sensors have some issues with the signal and are triggering a CEL but the mechanic seems to think that is not the problem.

Mind you, the temps are in the 90F range lately, so it's very hot ambient temp, too.

I am stumped. Help.

Post by **abscate** » 13 Aug 2015, 15:18

Go over your induction hoses by removing them, inspecting for splits, then replacing. A visual inspection usually misses problems on these.

This is a MM ETB car - has the throttle body been replaced?

The O2 sensors have to work on these cars - especially the front one.

PCV blockage is another possibility but thats rare on the late P80s and P2 due to better design.

Post by **sanfelice** » 13 Aug 2015, 15:30

PCV is partially blocked but my other car was worse and still ran.

I will check the smaller vacuum lines.

The O2 sensor is the front causing problems, I believe. Bank 1, IIRC.

The ETM is a yellow label '02 year model. This was done before I bought the car, although I am dubious it's any cause, as the car does run well cold.

Post by **abscate** » 13 Aug 2015, 18:58

I believe the default map runs the car rich if the O2 files not close loop, so as not to burn valves. That could be the hole rich running problem.

Post by **sanfelice** » 13 Aug 2015, 20:59

OK, thanks

The car does have an aftermarket downpipe and Catalytic and the O2 sensor location has never been ideal. In fact, I had a muffler shop fix it a while back to improve things and it did seem to improve for a short time.

Thanks again for the hint at a look toward closing that loop