'92 Lumina 3.1L start fine but sputter after warming up.

[lewispb00]

I have a '92 Lumina 3.1L sedan. I have recently changed the spark plugs and wires. After warming up, the engine will stutter and jerk under slight acceleration and if you get to a constant speed and then give it just enough gas to maintain. Also after this starts it has a tendency to die when idling or coming to a stop. The engine runs fine upon heavy acceleration and has plenty of power.

When I changed the plugs the old ones were gapped at .080 and I gapped the new ones at the proper .045. I thought that maybe it overloaded the coil pack so I changed it. That was not it. I also triple checked that the wires were routed to the correct firing order. The SE light wasn't coming on at all except once. It flashed code 32. I have changed the EGR valve, MAP/BARO sensor, and tested the IAT sensor. The light has not come on since.

I am out of ideas. Please help.

[Blue Bowtie]

Since the '92 is likely a batch-fire system, you can perform a manual power balance test of the injectors. Start and warm the engine to temperature, disable the IAC, connect a diagnostic tachometer or scanner, and disconnect one injector at a time while monitoring RPM drop. If RPM does not decrease or decreases less than for other cylinders, that cylinder is not producing the same power as the others. If a cranking compression or cylinder leakage test of that cylinder does not reveal a mechanical problem, the likely suspect is the injector for that cylinder.

[richtazz]

The 92 is a VIN-T 3.1, with the big flat upper plenum. Only two injectors are accessible with the engine assembled. First, what brand of plugs and wires did you install, and did you run all the wires perfectly parallel to one another all the way from the coil packs to the plugs? If you did, they can develop a magnetic field causing RFI interference with each other. Make sure the wires cross each other to break up this possibility. Cheap/inferior brand plugs and wires can misfire right out of the box.