1991 3.1 Runs rough when warm

[Jelly JoJo]

1991 Pontiac Grand Prix 3.1 liter will run great when the car is cold or not warmed up fully. The car runs very rough once it is warm and I have huge issues making it up hills while maintaining a speed above 15 mph. I have to lightly press my foot on the gas pedal for the car to accelerate otherwise it bogs down and runs rough again. When the car is cold I can rev the engine as much as I want and tackle hills with no issues whatsoever. I changed my crankshaft position sensor which solved a problem (car would die while driving), but this problem is a separate issue. Also, changed spark plugs and wires (triple checked wiring) and air filter. Check engine light only comes on when in park and when my foot isn't on the gas. Planning on trying to get a code read tomorrow and possibly get my hands on a vacum line tester. Any feedback would be appreciated. I have heard a lot of possibilities tossed around. ICM, TPS, MAF, Catalytic Converter, fuel filter/pump. I know it would help when I get some codes, but until then I was looking for any other suggestions.

[tblake]

Sounds like an injector is shorting out when warmed up. Its a PITA to test the resistance on the injectors on this car, but that would be what I would do. Any injector with less resistance than the rest is shot. They should all be right around 12-13 ohms. A little more resistance is fine, but any less and the current will all travel through that injector and not fire the rest (since your car is batch fired).