Knock In 2002 Chevy Malibu Engine

Why would a 2002 Chevrolet Malibu with a 3100 knock through the intake only when opening the throttle body.

Hello, is the sound like an engine knock or valve train noise? .Or more like a backfire.

Like metal hitting the inside of intake but only when giving it gas. its not a ping or backfire.

OK, that is a valve train issue. You could have had a rocker arm come loose or come off completely. Sometimes the threads pull out of the cylinder head.

It’s a higher pitched, metal hitting metal sound. May be a bent push rod as well.

It’s like if you took a wrench and was tapping the intake.

OK. If you listen very closely, you will probably find it coming from either side of the valve covers.

Yes, that is what it sounds like but i only hear it when the throttle is open to rev the motor. It also could be a bad lifter, and the noise is traveling up the push rod and rocker arm and sounds like it’s right there at the intake.

Giving it gas will make it louder. The sound comes through the air box.

Yes, that’s when this type of problem will make noise. At idle, the engine isn’t turning fast enough to cause the issue. You will need to remove the valve covers and look for the problem.

But Protech, the motor was rebuilt right before i bought it maybe has a thousand miles on it since and have you ever heard of the throttle sticking open on this motor.

Just because it was supposedly ‘rebuilt’, doesn’t mean it was done properly, plus a part can fail at almost any time. The throttle body on your type of vehicle is not known to stick open unless there is debris causing or it’s excessively carbon build up.

OK thank you for your help i’ll look at it in the morning.

You’re welcome! Have a great night.

How much would it charge to fix a knocking engine on a 1998 Chevy Malibu or what could be causing the knocking?

It depends on how bad the knocking is, and whether it is valvetrain related or something deeper like a rod knock. If it’s a rod knock, you’re probably looking at engine replacement which can run into the thousands. If the noise is valvetrain related, it can probably be fixed anywhere from a few hundred dollars up to a thousand.

1995 Chevy Lumina

Can you tell me why my car is starting to run loud and like it won’t slow down and it speeds on me when I press the gas and when I press the gas it gets louder.
You’re going to have to be a bit more descriptive of your problem.

What I’m trying to say is that it sounds real loud when I accelerate then sometimes i’ts like slowing down like it wants to stall. I was told that it might be a catalytic converter. Maybe you can get a idea on what I’m talking about. I’m not good with explaining it sorry about that the person that told me that is not a mechanic so i don’t know.

If the sound is like a loud exhaust, then yes you could either need a catalytic converter, or possibly have a rusted out muffler or exhaust pipe. Without hearing it in person, it will be hard to say exactly.

Yes i know OK thank you.

I have a Chevy Lumina APV and I am not sure as to where the ground wire is located? Also I am having issues trying to figure out what is wrong with my van. Every time I apply the gas it backfires.

I have replace many different part on the van and nothing has helped the vacuum is good on it there are no leaks and also all the pressure is good in it as well.

There are times where when I start my van it will hesitate and then die and then when i restart it and it hesitates then I apply the gas a few times in a pumping motion it will finally smooth out and run fine. HELP please.

Answer: Your car does not have a ground problem. It sounds like you have a leaking fuel pressure regulator. That would cause the starting problem you are having and also a backfire. When they leak, they cause the engine to be very rich, like an old car that is flooded. Hitting the gas a few times clears it out.

You would need to remove the vacuum line on the regulator and loo and smell for gas to confirm it is leaking.

More information here on the 3.4L fuel pressure regulator.

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