There must be a gremlin in this car! It’s a 1990 Pontiac Grand Prix LE 3.1L engine, 170,000 miles, A/T. It was a dark and stormy night…Wait! Wrong story. It died. After considerable efforts at resurrection, it revived to the point where it idles. The details: While driving, it stalled. Would not restart. Timing chain? Replaced worn chain. Still, no start. I used a multimeter and followed the scan charts as much as possible. Changed Throttle PS, MAP, IAT, CTS, IAC valve, and spark plugs (sooty). The coil pack, Crank PS, spark plug wires, air and fuel filter, and fuel pump were changed last year by someone else chasing this gremlin. Current condition: the engine will idle at 1,000 rpm with the fuse pulled which powers the EGR valve and the purge control valve. It is a digital EGR valve (three solenoids). With the ignition key in RUN, engine off, the voltage on ECM terminals A4 is 0.5, on A19 is 0.3, and on C13 is 0.0. Unplugged A,B,C,D terminals and took ohms measurements. They were A4 is 28, A19 is 27, and C13 is 16 (the resistance of the egr solenoid coils). The P/N switch and the Power steering switch checked good. With the egr/purge fuse in, it won’t start. Without the fuse, it will maintain an rpm of 2500, in neutral, smoothly. Go above that, and the engine roughens and the rpm starts to fall off. In Drive, it begins to roughen at 1200 rpm, and won’t go any higher, and will die if pushed further. While running, the fuel pressure gage stayed at 37 psi at 2500 rpm in neutral. In Drive, as the throttle is opened to 1200 rpm, the fuel pressure increases to 45 psi. My bright ideas have all dimmed. Do you have one? Do you have a gremlin blaster?
I don’t know the control mechanism for the fuel injectors on this car, but I would suspect that. Or multiple fuel injector failure…