Why do it make a knockin sound every time step on the gass

Asked by Mar 15, 2016 at 07:20 AM about the 2004 Pontiac Grand Prix GTP

Question type: Maintenance & Repair

Under my hood of my 2004 grand pri it
makes a knocking sound

4 Answers

73,055

Possible low octain fuel, may want to try a tank of premium gas, or if the knock is low in the engine, then a rod bearing starting to go.

1 of 1 people found this helpful.
98,445

Bad rod, broken piston though these tend to make noise all the time, carbon build up on a piston, blown headgasket between two cylinders.

1 of 1 people found this helpful.
355

Possibly valve problems in your cylinder head or maybe loose or worn rod and main bearings, although your water pump on that model can also produce loud noise if failing.

735

Check for low oil. Harmonic balancers will knock as well when they are going bad.This is on the crankshaft pulley on the bottom of the engine.

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