ploblem when running in high speed above 50 mph my check engine will light up. code p0300. 4 cylinder i replace all sparkplug and cable no help, replaced both coil no help. engine running great in backup mode. i'm getting 25 mph in backup mode. need help
Need to change fuel filter and check fuel pressure.
Doc
Did you put GM plug wires on? If not do so... Aftermarkets are not good..
Alan
Sure they are. I prefer Accel wires over Delco for performance reasons.
Doc
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