Hello everybody!
My volvo is a 1990 740 GL Regina fuel system. 145,000 miles. I have recently gotten a job where I am now having to drive it around 70 miles a day to work and back. I have recently changed spark plugs, wires, timing belt & tensioner, transmission fluid and filter screen, radio suppression relay, all accessory belts, changed oil, fuel filter, and cleaned the throttle body.

The car has always dropped to about 500 rpms when shifted into reverse when the engine is cold. However, recently I have been giving it gas in reverse to back out of my parking space & when I let off the gas it will stall out. I can work the brake & gas to keep the engine rpm up when shifting to forward, but it will stall out without any extra help. After that, it idles fine. I get in the interstate & it runs normal. After driving 32 miles, when waiting at the traffic light at the off ramp, it idles at about 500rpms & is very rough. When I go to give it gas again, it drops rpms but then surges back to normal driving rpm. If I put the car in neutral or park at this time, the idle surges between 600-900rpms.

When leaving work, everything acts normal.

I had what almost seemed like a miss when idling, so I cleaned the throttle body & put fuel system cleaner in the tank. That fixed the miss, but now it is doing what I described above. After the throttle body cleaning, my idle speed was adjusted correctly.

It also has a low sounding misfire when coasting on the interstate, which I know could be a rich condition. However no codes are on the obd system. I had a code months ago that referenced the O2 sensor, but that hasn't come back. Is this related to the idle problem?

I replaced my transmission fluid & filter because I had a whining sound that would wind down as I slowed down. My shifts smoothed out & the whining went away. I had a slight leak in the hose that goes into the side of the pan that I have since fixed, but I think I slightly overfilled the transmission when topping it off. Now my shifts are harsh again & the whining sound has come back. Could this have anything to do with the idle?

I know I'm getting close to the mileage where I need to change my fuel pump.

Does anyone have any clue what my problem/problems could be?

Thanks,
Ben