I have a 99 grand prix gtp that we just recently purchased that was not running when we got it back to the shop I charged the battery and started it for the first time it was random misfiring and running poorly. I swapped the ecm changed the coil packs plugs wires changed fuel filter and checked voltage output and fuel pressure and it started to idle but ruff but as soon as I put it in gear it all came back or if I start the ac any kind of load then it goes all to crap with no dtc's.
Country: United StatesMake: Pontiac
ecm,plugs,coil packs,wires,battery,fuel filter,checked fuel pressure and voltage and checked for trouble codes. HELP :(
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