Oops, I think I just posted a half message so let me put the other half down. I have a 1993 850 (134000 miles). I think that surging idles and occassional stalling is a common problem with this line. I am simply amazed at how little support Volvo offers through the dealership mechanics on a car that has been in production for over 10 years. I am pretty turned off by that.

1st time I had problems, the car would idle erraticly, would pause and shudder under pressure and it got worse in cold wet weather. The dealer had no idea. I replaced the throttle control unit and fixed the problem.

Last year, the car would stall occassionally at highway speed and would idle erraticlly. I replaced the fuel pump relay and fixed that problem.

Few months latter, bad idle again. I cleaned the battery terminals and the flame trap and fixed that problem.

Here I am again with an erratic idle at start-up. It surges and relaxes and there is a sucking sound coming from the Throttle body area that sounds like it opening and closing. Occassionally, usually while letting off the gas and applying brakes, all dash lights come on and the car comes to a calm quiet stop. I have been monitoring the voltage off the battery because I thought it might be a voltage regulator/alternator problem. The voltage seems within spec. I am not suspecting the idel air control unit is bad and will be looking at it this weekend. I also woner if the Oxygen sensor could be the trick.

Good luck
John