Tapping/ticking noise

Tac Map Mike · May 24, 2023

Hi there, I have a 1991 gmc Sierra 2wd Reg cab. No engine codes. Rough idle (been there a long time). New plugs, wires, rotor, and cap.

Today it Just started making a tapping noise (sounds like metal on metal) on the driver side. Doesn’t sound like motor knock. Almost sounds like a rocker arm or something? I pulled off the valve cover and some rockers have a bit of play but I didn’t feel like tackling those today or even know if that’s the problem. Doesn’t happen in park - only in drive on acceleration. Doesn’t seem to matter if it’s warm or cold.

Any ideas?

Gramps · May 24, 2023

Pull the inspection cover on the trans. Look at the flexplate look for a crack or cracks. Might need an inspection camera to get up near the bolts. Other option is pull the trans anc converter back but that’s a lot of work.

Tac Map Mike · May 24, 2023

Gramps said:
Pull the inspection cover on the trans. Look at the flexplate look for a crack or cracks. Might need an inspection camera to get up near the bolts. Other option is pull the trans anc converter back but that’s a lot of work.

I never thought of that - thanks!

Schurkey · May 25, 2023

First Guess: Broken flexplate, as already mentioned.

Second Guess: Exhaust leak, worse under load.

Third Guess: Valvetrain noise, including but not limited to broken valve spring. Might also explain rough idle. Does not explain why it's worse under load.

Tac Map Mike · Jun 6, 2023

this turned out to be the exhaust manifolds leaking btw

Tapping/ticking noise

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