I have a 1990 740 GL, 180K miles, Regina injection, fairly well maintained and normally trouble free. A couple of weeks ago the car started running rough and stalling. I knew that the ten year old battery was getting weak and I thought I might be getting low voltage that was confusing some of the sensors. New battery later the motor spins up faster and the car starts easier but still has hesitation. I then cleaned the throttle body, checked the plugs and wires (cap and rotor are two years old and should still be good), looked for vacuum leaks, and then called upon the Volvo gods to smile upon me and make the car run right so that I can have my pickup back from my wife - still runs rough.

Here are the symptoms:
Cold starting and idle are good.

There is a stumble when you open the throttle and close the throttle (feels a little like a carbed car with a bad accelerator pump).

When warm, after driving for a couple of miles, the car will die most of the time when you come to a stop while in drive, sometimes it stumbles and the idles up to 1500, bounces a little, and then settles back to around 800.

Accelerating at highway speeds was never very good, now it is much worse.

I did clean the connectors for the AMM, TPS, and injectors, and the TPS connector was full of oil. Also tested the AMM by unplugging it and it ran much worse unplugged.

This one has me scratching my head. I am suspecting the TPS or the very expensive idle control valve, but have sort of hit the head scratching phase.

Also, will one of the OBDII universal code readers work with this car?

Any thoughts would be greatly appreciated, someone here years ago helped walk me through a wiring harness rebuild on an 83 240 and I still appreciate that.

Mike