Marbles in drivetrain - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 06-07-2000, 04:45 PM Thread Starter
 
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Marbles in drivetrain

What's it mean when you hear marbles rattling around from from drivetrain area when accelerating heavy or starting from a stop in a car with auto tranny? When that happend in my Camaro, it meant I put something less than 93 octane in it. Is that pretty much the problem and solution, or is there more to it?

Thanks

Sean

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post #2 of (permalink) Old 06-07-2000, 05:49 PM
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Re: Marbles in drivetrain

What you are hearing is called detonation. It is the sound of the fuel/air mixture igniting before the spark plug ignites while the piston is still traveling up to the top of the cylinder. Ignore it and you will most likely burn a hole in your piston, break the piston, etc.. It can be caused by a number of factors. Ignition timing too far advanced, too hot of a spark plug, carbon buildup in the combustion chamber, poor fuel, vaccuum leaks, lean fuel mixture, and/or ignition components (cap,rotor,spark plug wires, spark plugs) which are in poor condition. Your best bet to attempt to cure it is to do a complete tune up. Change the distributor cap, rotor, spark plug wires and plugs as well as checking the timing. Also check the condition of your vaccuum lines and replace any questionable ones. A vaccuum leak can cause a lean condition which may cause detonation. Try those first and seek more help from this BBS if it doesn't go away.

post #3 of (permalink) Old 06-09-2000, 12:28 AM
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Re: Marbles in drivetrain

besides detonation, you could be hearing the valves rattling around in a worn engine. My Jeep does this number...93 seems to help some, but too expensive for me. I think this is caused by the valve springs getting weak with age. I recently replaced a worn motor mount, and the rettling went away almost completely. Try checking for worn mounts or any other causes driveline vibration

Chris Allmond...89YJ/33"/2-3"lift: engine\tranny\rearend swap in future
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post #4 of (permalink) Old 06-09-2000, 06:14 AM
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Re: Marbles in drivetrain

It could also be a "carbon knock". Mopar sells a product called "combustion chamber cleaner" which is very good stuff. It is about 70% water, and comes out of the can as a foam. Run the engine until it is hot, remove the air filter, and spray it down the carb when the engine is idleing. When about 3/4 of the can is empty, shut the engine off and let it sit for 10 minutes. Then re-start the engine and run the rest of the can through. Then drive it down the highway until the smoke is gone. This stuff is really great, and for some reason, not very many people use it. Hey for $6. you can't go wrong. To finish the job off, try a can of B.G.'s 44k injector cleaner in the tank. That is about $20 a can, but worth every penny.

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