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04-08-2015, 05:40 PM
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#1 | |
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AF Newbie
Join Date: Apr 2015
Location: Cedar Bluff, Alabama
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Motor knocking
I have a 1988 GMC Sierra, 350 4x4
This just started. It runs and sounds fine just sitting there. Whenever I put pressure on the motor while driving, it starts knocking. I can rev it up in Park and it's fine. Only does it under pressure . HELP!!!!!!!!!! |
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04-08-2015, 07:18 PM
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#2 | |
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A990 racer
 Join Date: Mar 2002
Location: Chestertown, New York
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Re: Motor knocking
You need to have someone listen to this onsite, we can only guess from here.
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04-08-2015, 08:25 PM
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#3 | |
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AF Newbie
Thread starter
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Re: Motor knocking
Sorry, not sure what you mean?
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04-08-2015, 08:34 PM
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#4 | |
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AF Enthusiast
Join Date: Dec 2001
Location: clarksville, Tennessee
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Re: Motor knocking
He means have a mechanic come to listen to it.
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04-08-2015, 08:43 PM
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#5 | |
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AF Newbie
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Re: Motor knocking
Cedar Bluff , Al. Looked everywhere here. No mechanics. Afraid to drive too far. Surely someone has an idea.
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04-08-2015, 08:45 PM
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#6 | |
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AF Newbie
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Re: Motor knocking
Don't get it. Happened all at once. Should be something simple. No signs at all.
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04-08-2015, 10:28 PM
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#7 | |
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AF Regular
Join Date: Dec 2012
Location: Portland, Maine
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Re: Motor knocking
Usually if it were a rod or valvetrain knock, it would happen at idle, while revving the engine in park, and under a load. When it only happens under a load it's usually a spark knock, which is an ignition timing issue. Not as serious, but it does need to be fixed or it can lead to more serious issues.
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"Ok, systems check; the battery is discharging, the oil temperature is very high, the oil pressure is very low, the engine temperature is off the end of the scale, I'm running out of petrol... but the clock is correct!" -James May, in an old, worn out Lamborghini purchased for less than £10,000. 
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| The Following User Says Thank You to MikeCStig For This Useful Post: |
Igenofish (04-09-2015)
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04-09-2015, 01:36 PM
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#8 | |
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AF Newbie
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Re: Motor knocking
Had timing checked today. It's right on. Back to the drawing board.
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04-09-2015, 11:46 PM
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#9 | |
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AF Enthusiast
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Location: clarksville, Tennessee
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Re: Motor knocking
only in drive. then driveshaft, gear box, tranny...etc..
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04-10-2015, 09:37 AM
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#10 | |
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AF Newbie
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Re: Motor knocking
Will lok into that. It's just that it definately sounds like it's coming from the engine. Almost as if it were bad gas. Tried to remedy that also. I'm just lost here.
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04-10-2015, 04:58 PM
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#11 | |
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Your worst nightmare
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Re: Motor knocking
You need to check your ingition system, from your plugs to wires, to cap to rotor. I bet you'll find your issue there,.
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04-10-2015, 05:08 PM
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#12 | |
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AF Newbie
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Re: Motor knocking
I have replaced plugs rotor button and Cap already. Wires look good in the dark, but haven't replaced them. Truck runs like a champ until it is put under pressure. Driving only. In park, sounds fantastic.
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