Knock in '88 Chevy Beretta 2.0


Old 01-01-11, 11:06 AM
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Knock in '88 Chevy Beretta 2.0

Okay, it seemed like too good a deal to pass up. I bought a 1988 Beretta with the 2.0 litre pushrod engine and 5-speed transmission for $250 and drove it the 20 miles home.The whole trip it made a knocking noise that followed RPM's. Investigation at home revealed a bent pushrod (#1 exhaust). I straightened and reinstalled it, hoping (of course) that I had cured the knock. Naturally, I'm posting because it hasn't completely gone away. It really only shows up when I add right pedal; seems to go away at steady engine speed.
Not being too deep in the car wallet-wise, and not wanting to get very much deeper, I'm hoping for further valvetrain issues. But I'm not familiar enough with noise-based diagnosis to tell whether I'm looking at possible piston pin(s), rod or main bearing(s) or just more valvetrain slop. Anyone have direction for me? Thanks tons in advance - trying to get this car in shape for 17-year-old stepdaughter to learn to hate it pretty quickly! - Chris
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Old 01-01-11, 11:29 AM
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The only thing I question is how successful were you in straightening the pushrod?? Couldn't you have replaced it as easily? It would have eliminated that area of concern. Next would be run compression checks on the cylinders. Something bent the pushrod....cure the cause.... cure the problem.
Old 01-01-11, 02:01 PM
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Thanks, chandler. Checked the pushrod after straightening against the aluminum block that showed it to be bent and all the others straight. It was a quickie, cheap, try-it-out kind of fix, cool if it worked, no bucks out of pocket if it didn't. Yeah, a new pushrod was only $3.50, but no trip to the parts store made it worth a try!
Old 01-01-11, 08:49 PM
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I woudn't think a push rod would cause a knock. But I would be looking at what might have caused it to bend. Try pulling the plug wires one at a time to see if you can change/eliminate the noise. We used to think in terms of main brngs for a knock under load.
Old 01-11-11, 08:40 PM
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I have come across several of these engines with a bent pushrod or two. Never could find a definite cause other than overrevving, esp. with a standard trans. Never had any come back with any other issues after replacing bent pushrods. Compression was always good with no indication of bent valves.
I would replace the bent one, check all of them, and see what happens.

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