1990 740 non-turbo wagon, 243K. It stalls at idle when begining to accelerate but if left to sit a few minutes will fire up for one second but runs poorly and dies. Left over night it will start and run for a few minutes before stalling. After I did the items listed below it idled and ran excellent for about 20 miles (but it also had sat for a month waiting for me to complete the work).

Things I have done:
Removed and cleaned the throttle body(didn't touch the TPS adj.)
Replaced lousy intake gasket
Cleaned and replaced flame trap and related plumbing
Cleaned idle air valve and checked for operation
Soldered fuel pump relay and also tested with a known good one.
Giggled and wiggled everything else.

The problem begins as a slight stumbling at an idle while trying to accelerate but then ran flawless at cruising speed. After a few times noticing these small stumbles at idle it then stalls and that’s it… won't start.
The crank sensor wire looks ratty with some broken insulation but the car did start and run well after the work I did. I thought the fuel filter or pickup screen might be getting blocked but someone on the board suggested that would be more troublesome under load, which makes sence and not at an idle with lower fuel demand.

Once, before I did the work and after letting it sit for a few hours, I was able to get it started and keep it running by pumping the gas peddle as you would with a carburetor and drove it home 5 miles.

I would appreciate your input before I start replacing more stuff. Thanks a bunch, Butchie

http://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm
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Post Back. That's whats makes this forum work.

Hi Aleekat,
Thanks for link to the obd box FAQ and to mmal231294 for getting me looking for codes. We've had this car about 7 years and I didn't even know it had an obd port. I've been all over the 700 FAQ's over the years but I never was looking for it. Live and learn.
I got only a 3-2-1 code which indicates the radio suppression relay. Interestingly, after a slight stuborn start today the car started and settled down to a smooth idle. I let it run about 10 minutes reving it and letting it idle and took it around the block where a small amount of hesitation was noticed on acceleration but it didn't stall. I cleaned up the coil and its attachment points to to rule out any problems there(thanks to chris herbst recomendation for Regina cars in one thread). After doing that I started it up and when reving it went to 3k rpm and stayed there until I unplugged the IAC valve. Then all back to normal after reconnecting the IAC with still some hesitation on initial acceleration(feels like a bad acc. pump would feel) and maybe more pronounced when taking a corner. Some kind of gremlin in there. Still fussing with it. Thanks all.

If you got a 321 code best deal with it. Contrary to it's name the RSR supplies power to the fuel injection system including the injectors. If it goes flakey engine will run flakey. if it goes bad engine will not run, period.

I would replace or resolder it as your next step.
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David Hunter

The OBD in your(and my) vehicle is primitive compared with later OBD2 but still can point you in the correct direction. If you have never replaced the RSR its a $20 part and takes all of 5 minutes to replace. To me its one of those items like a fuel pump relay where they are so cheap and so easy, it makes sense to replace them to A)Rule them out and B)They are common points of failure so if they havent failed yet...they will. Same with Fuel Pressure regulator although thats like 50&...oh and the Power Stage but thats like 80$...I could go on and on....Good Luck.

Classic symptoms of a possibly bad AMM. Pull the connector off the AMM (with the ignition off). Try to restart. If it can't see the AMM it will go into "limp home" mode where it attempts to run without knowing air flow. If the engine now starts and stays running (albeit a bit rough) then it's almost certainly the AMM.
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Dave -940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,
Thanks for the input. I believe my system to be a Regina and I don't think what apperars to be the AMM is actually an AMM. I could be wrong but mine dosen't have that large 6 pin box that accepts the plug like a bosch system AMM but mine has a simple 2 prong plug. I will try to unplug that tomorrow and see what happens. Thanks

Are any codes produced?

I'm not up on getting codes on the 740. I have an Acton reader I used on newer cars I own but not sure if there is a plug on the 740 or how to retrieve codes.
Can you give me any hints? Thanks.

Mine will only run for a few minutes if the o2 sensor goes bad. Did you check it? When was the last time it was replaced?