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91 GM Engine Miss with Code 33
Greetings,
Have a '91 GM 5.0L engine with 140K Miles...that surges & runs rough when NOT accelerating...does it in 3rd gear...so it is not the auto tranny. Idle & top end power are great.
Got 2 digit code of 33..."EGR valve not opening;insufficient flow detected"
So...I cleaned & checked EGR valve...seemed to work OK on bench with about 4" of vacuum. I then disconnected vacuum on EGR valve(plugged vacuum line), drove car and missing/surging went away...but there was a lack of power and acceleration.
Did electrical check of Throttle Position Sensor(TPS)...it checked out OK on the bench with a smooth change in resistance.
Replaced Electronic Vacuum Regulator(EVR) that controls the amount of vacuum to EGR valve. Engine still surges and runs rough after reaching driving or floating speed. Fuel filter, air filter, plugs, rotor, cap, etc. were all replaced and/or seemed to be OK. I have NOT changed PCV valve or the small air breather screen at the back of the engine.
So...My thanks in advance to anyone who can give me any suggestions to cure an engine miss at cruising speed with code 33.
Art Gladfelter
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