Figuring out the knock and adding performance - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 04-26-2006, 12:56 PM   #1
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Default Figuring out the knock and adding performance

The car: 1992 Bonneville SE 3.8 no supercharger.

Car has a loud knock, I haven't even run or driven it yet to see what else is wrong (I can hardly imagine) My brother says it is running on 5 cylinders, thats what his friend told him and he has been driving it short distances the way it is for 8 months or more. What can am I looking at here? Is this major? Suggestions would be good because I am unable to work on this until the weekend. I just want a list of things to check.

P.* Are there speed parts for this? I don't want a race car but with only 160 hp or whatever, it would seem to me not very fast.

Thanks allot in advance,
Chris
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Old 04-26-2006, 01:22 PM   #2
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First thing you need to do is replace the plugs and wires. Let'* get this thing firing on all 6 first.

After that, maybe you can describe the 'knock' in a little more detail. At idle? Does it go away when you accelerate? Which side of the engine do you hear it from more?

You can liven it up a bit, and make it decently quick off the line. These 3800'* are known for their low-end torque. And not just the supercharged motors either.

Take some time to read through Techinfo at the top of the page. Alot of your questions may be covered there.
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Old 04-26-2006, 01:23 PM   #3
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well my friend is having that almost same problem on his 3.1 so i will ask him and see what he says but i doubt it is the same problem but he is also familiar with 3800 he has a 92 ssei(supercharged) dont think it will help but will see
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Old 04-26-2006, 02:01 PM   #4
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The knock is constant. It does not go away no matter what speed the motor is running at. When I take of it sounds pretty bad, a little hesitation but not allot of power. It almost sounds like combination exhaust leak and HOT cam. Someone also suggested that the intake or exhausr vavle lobe on the cam shaft could be worn out and causing it to bake fire thru the intake........
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Old 04-26-2006, 02:10 PM   #5
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To start off...since you don't know what you are dealing with, you may want to pull the plugs one by one and find out which cylinder has the problem.

Not sure if the harmonic balancer can cause this type of noise..but look it over and see if the rubber is pushing out.
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Old 04-26-2006, 02:32 PM   #6
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Oh yeah and it sounds like a knock, but not a metal on metal grinding knock........
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Old 04-26-2006, 02:41 PM   #7
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Skip the balancer thought. It shouldn't be a knock on acceleration. Apparently the stops would push against each other and there would be no noise while accelerating.
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Old 04-27-2006, 03:09 PM   #8
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Any other tips guys???
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Old 04-27-2006, 03:18 PM   #9
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Quote:
Originally Posted by mrbell83
Any other tips guys???
Did you pull the plugs to see what'* going on? Or change the plugs and wires yet?

Other than that..no thoughts yet. If you find out what cylinder and how bad...then there will be more to go on.
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Old 04-27-2006, 03:22 PM   #10
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Well truthfully, you don't really want us to just start shooting from the hip on this do you? That is the quickest way I know to relieve your wallet of it'* green matter. The thing about diagnostics in most instances, is that they start with the simplest, least expensive possibilities and go from there.

IMO, as already said, diagnosing an engine you're not familiar with (meaning - it'* condition) starts with the tune up. This gets you looking at things like the condition of the plugs, wires, coils, vacuum lines, etc. While these items will not likely fix your knock problem, their conditions can give you valuable hints as to what may be wrong.

Keep your computer nearby and let us know what you find. We'll be here to offer what advice we can.
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