99 Chevy Malibu 2.4 Quad 4 knock

[Oil stain]

This motor has 92k on it and now has a loud knock coming from under the valve cover. I'm going to be opening it up in a couple of days to see what's causing it. It definitly sounds like a valvetrain issue.

Has anyone had this issue and can give me an idea what might be causing it?

Thanks,

Oil Stain

 

[Big Smoke]

Just did a search and wanted to bump this up. I was going to ask the same question about a 1998 Malibu with the same issues. Any Ideas?

 

[rpn453]

Any chance it could be regular engine knock? I'd check the knock sensor first, and maybe try premium just to rule that out. My mother once got a bad tank of gas in the same engine and had some knock.

 

[55Test]

The Quad 4/Twincam use a timing chain, so it could be the chain making the noise.

 

[Chris142]

Those did have trouble with the timing chain runners.

 

[Ben Boyle]

We have a '97 Malibu with the same engine and earlier this year it did the same thing. Turned out we spun a bearing. A trusted mechanic said that he has seen many of these engines do this at around this mileage (ours had about 93k on it). But since the car has always just been a spare car we had a used engine put in and we'll see what happens.

 

[Oil stain]

I found the motor had 2 spun rod and 1 main bearings. You should have seen the sludge inside of that motor!

 

[rpn453]

How long have you had the car, Oil stain? Any previous maintenance records if not bought new?

My mother has about 100K miles on hers now. The oil always looks good.

 

[Oil stain]

quote:

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Originally posted by rpn453:
How long have you had the car, Oil stain? Any previous maintenance records if not bought new?

My mother has about 100K miles on hers now. The oil always looks good.

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It wasn't my car. A friend bought it from a family member. The kid only put about 1500 miles on it before it died.
Once I started taking the motor apart you could see the crud everywhere. Even the inside of the intake was really bad.

Right now I'm putting a reman v8 motor in a firebird for the same reason, a spun rod bearing. In the beginning of the year I put headers, a catback system and 1.6 rockers arms in. When I had the valve covers off and doing the work, the heads looked real clean like the owner really took care of the motor.
When she came to me about the rod bearing I thought she just over revved the motor. But to my surprise, once I took the intake off, there was the crud. It was caked everywhere. It reminded me of the stuff that sits in the bottom of the BBQ.

So, the point is that even after looking in the oil filler hole or taking off the valve covers to check what you would think would be a clean running engine, can lie to you because someone had a valve job. Which as you know the heads get cleaned up.

To sum up, you never really know what your buying.

I happen to have taken a picture of the motor. The crud was real flakey and about 3/8" deep.
You can even see the gaskets didn't seal well. It's no wonder the bearing went. It clogged an oil passage somewhere.

[ September 05, 2006, 09:19 PM: Message edited by: Oil stain ]

 

[55Test]

quote:

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Originally posted by Oil stain:
I found the motor had 2 spun rod and 1 main bearings.

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And it still ran??

 

[Big Smoke]

Thanks for the answers so far. Here is a little more detail. Bought the car from a friend who has owned it since new. I know it has been well cared for. Oil changed regularly with what ever dino the GM dealer had. The car now has 78,000 miles on it. He had a timing chain put on about 5 months ago after the water pump needed replacing. The car is quiet and smooth when its cold and after a 70 MPH 20 mile run to work is sounds terrible. When first started in the morning sounds like a bunch of lifter rattle for 1-2 seconds, then quiet until its warm. He said the car never sounded like that until after the timing chain was replaced.

I have only had the car for a month and so far I have only replaced the plugs hoping to eliminate the rough idle (did not work). I have also done some brake work and of course on oil change with Pennzoil 5W-30 and a bottle of SLOB (after reading about it on here).

I just filled the car up yesterday. I will try a tank of 93 at the next fill to see if its the knock sensor. I know the car has only had BP regular in it for most of its life.

If its the timing runners is that an easy fix? Is it worth fixing? This is a second car for me and I bought it just for back and forth to work which is 200 miles a week. If its a bearing, what should I do? Run it into the ground? Maybe its time to start using the stash of free Maxlife and hope for the best.

Thanks so far for all of your help.
Bill

 

[Oil stain]

It's possible that the timing chain has not mated well with the timing gears.

Try fuel injection cleaner from Chevron. It's in a black bottle.

 

[Big Smoke]

I already used I bottle of injector cleaner Valvoline Synpower. I will try the Chevron stuff. Is the chain something to worry about or will it correct itself after wearing in somemore?

 

[Oil stain]

That noise might be there for a long time. I know it says in the manual, that before removing the old chain for doing head removal work, that you should mark the chain and gears so that they mate up correctly upon installation when using the original chain.

So, I would think that a new chain will be noisy because of its fitment with the slightly worn gear.

Now, should they have replaced the gears? You would think so. Because of what I said before.

What puzzles me is on these cars is why do you have to change a timing CHAIN unless it is worn and they do have a tensioner. Chains are pretty much a life time thing verses lets say, a timing belt.

 

[Big Smoke]

I know the timimg chain work was done by Goodyear. On the bill it says "Timing Chain Kit" I would think that means everything should be new. I still don't know why the timing chain would need to be replaced for a water pump job? By the looks of it everything needed to come off but why would they not re-use the old chain / gears? Maybe it has something to do with the $625 they got for the timing chain kit alone.