1991 740, regina car, 120k
Have been suffering from sputtering, coughing, backfires and finally stalling after running for about 15 or 20 minutes. This happens if I drive the car or if it's idling in the driveway. Sometimes this happens on startup when the temperature outside is in the high 80's, after sitting in the parking lot at work. If the car doesn't completely stall, will startup and run fine for another 15 mins or so. There is no throttle response when this starts to happen, and the tach will bounce around from 0 to 500-700, and if the car doesn't stall, it will recover and rev to 2k and then run fine.
I've replaced the crank sensor about 9 months ago, has new plugs and wires. I've swapped out the IAC with a known good part. All vacuum hoses are newer silicone tubing, no cracks in the intake hose.
Working on it tonight, no codes and the CEL isn't on. I disconnected the intake air remp sensor and nothing happened to the idle.
Current theory is the MAP is failing. Before I throw a new intake temp sensor and MAP on it, I'm asking my fellow brickboard hive-mind for help.
Someone else must have had this issue, any help is greatly appreciated.