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Red! 1985 4+3 man-trans! Car starts, will run for a while, then quits for no obvious reason! Whether sitting still, or going down the road! 2:00 min's-10min's. Sometimes it starts right up, other times it's gotta sit! No codes! Fuel pressure stable! Something interfering with injectors? Wires checked, everything that should work, seems to! The guy looking at it now, builds engines, his neighbor taught at G.M school, and they're both lost! It's a widget, thing-a ma-bob, whatcha-ma-call-it, WTF, something, that I know is going to be a simple fix...but what? Anybody had same experience! This makes my 84, with THAT issue filled Crossfire, look like it was made by RR!
If it quits while sitting still and throws no codes, you can fairly safely rule out sensors or any other circuit with feedback into the ECM. So that leaves the mechanical components of combustion--spark, fuel, compression. The last one can't be it since you didn't say it runs like crap, just that it spontaneously dies randomly. So fuel or ignition.
You say fuel pressure is good, but have you left the gauge on while it's running and watched it until the engine dies? You say it can die while sitting, so this should be easy to do if you haven't done it yet.
If fuel flow really is good, spark is next. Since it dies completely rather than dropping a cylinder, I'd ignore the wires and spark plugs and look at the ignition coil and ignition module as they supply all the cylinders.
Measure the resistance of each fuel injector. When I first got mine running it would run for about 20 minutes and then shut down. It turns out I had one injector that measured a much lower resistance than the other seven. This caused the ECM to go into safe mode. Replacing all the injectors solved the problem.
Measure the resistance of each fuel injector. When I first got mine running it would run for about 20 minutes and then shut down. It turns out I had one injector that measured a much lower resistance than the other seven. This caused the ECM to go into safe mode. Replacing all the injectors solved the problem.
I agree, My 89 run like crap until i changed the old multechs, those engines were never designed to handle modern fuels.
Baffled!
