David:
sounds like your voltage regulator is going bad. take car to autozone or somewhere and have them check.

Update on Stalling: Well it stalled with AC off. Decided to change the fuel pump relay per Klaus. Its been in awhile and no stalls yet. "Touch wood".

First I want to thank those of you who responded. You guy's are very helpful.

I decided to take the 850 back to the dealer for a re-inspection of their work given the fuel pump is not the total problem (old pump did have pressure fluctuations below normal range). They had it all day, no charge, checking-fuel delivery system, ignition circuits, speed sensor, cam sensor, electrical, etc and found them OK. Could not duplicate a stall either. They did note the AC was shutting down and blowing hot. Compressor temperature was 280 degrees at shut down. They let it cool down then turned AC back on. RPMs Dropped from 750 to 225 when compressor engaged. They suspect the compressor is failing internally and locking up, which may cause stalling at low RPMs when slowing or stopped. Transmissiom is an automatic.

I will drive it with AC off a few weeks and see if it stalls or not.

Can anyone validate this posibility? I know I need AC work as it is blowing hot during high outside temperatures. The freon is OK, no leaks in system, but the compressor is sounding loud.

Thanks again.

Could be an idle control valve. Not a huge repair, but not a d.i.y. either.

If not that, it might be worth looking at plugs and distributor cap...I know it sounds funny, but this has a way of smoothing out the engine, especially at starts and idles.

Otherwise, it's a fuel issue. To save a buck, just have the filter changed first and see if that helps. No use getting a whole new pump when a 50 dollar fuel filter change might do.

I hate it when dealers do the most expensivve things first!

When was the last time you replaced the fuel pump relay?

Klaus

Maybe replace your ignitiion switch. Your due for a new one.

If it only stalls while you are slowing down (nearly to a stop) you could suspect the lock-up torque converter in the gearbox is sticking. First course of treatment would be to verify trans fluid is fresh and clean.

If it also stalls sometimes after you have already been stopped for some seconds, suspect something else because the lockup would have already disengaged and wouldn't go back in without added pressure. I wonder if there is some dirt in the fuel tank. This happened to me on an older Volvo. Random stalling and severe hesitation, much more frequent on a downgrade. It was so bad I replaced the tank and the fuel pickup line, which resulted in 100% cure.

Another possibility (assuming ignition is ok) is something in the primary wiring - main relay, ignition switch, etc.

Measuring fuel pressure and main voltage would be helpful - one or the other may be fluctuating a lot (they shouldn't much at all) but only occasionally reaching an extreme value at which time the engine dies.