just picked up a 1987 grand national, very stock , under hard accel and boost car spits and backfires has factory boost gauge and aftermarket gauge they seem to peg when this happens . any help?
I have a pristene 87 in my shop right now doing the same thing you describe, pings and knocks only at full throttle is a 40k mile example, fuel sample for quality checked good, engine mechanical all checks good, its as if timing is too advanced(which is computer controlled by ecm) or turbo is overboosting intake charge. you should always check fuel and ignition systems thoroughly as well as mechanical. not sure how to check for this problem because repeated pulls in the current state could cause engine failure.
had the same problem with my 87 t type found when removed hoses from boost control solenoid they were cracked replaced hoses works great now car only had 3900 original miles