engine knocking when under load..? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 08-28-2000, 09:37 AM Thread Starter
 
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engine knocking when under load..?

When my engine is completely warmed up, like after driving for a while, I noticed that I get knocking when it is under a load...example, when I am going uphill in high gear and floor it. Sounds horrible, so I tend to baby it. Any ideas on why it does this? remember, it doesn't do it before it is completely warmed up. I thought maybe timimg, but the timing is right...

78 CJ5 w/360
"measure it with a micrometer, mark it with chalk, and cut it with an axe"
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post #2 of (permalink) Old 08-28-2000, 10:30 AM
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Re: engine knocking when under load..?

Jeepsternaut,
Here are few things you might wanna try;
1. Use premium fuel. [img]/wwwthreads_images/icons/smile.gif[/img]
2. Check your EGR valve. [img]/wwwthreads_images/icons/frown.gif[/img]
3. Hope is not a "rod knock" [img]/wwwthreads_images/icons/mad.gif[/img]

Good luck,

Nycjeep88 [img]/wwwthreads_images/icons/smile.gif[/img][img]/wwwthreads_images/icons/wink.gif[/img][img]/wwwthreads_images/icons/cool.gif[/img]
AIM: nycjeep88


post #3 of (permalink) Old 08-28-2000, 10:46 AM
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Re: engine knocking when under load..?

There was a post in the last three or so weeks about a similar condition caused by a weak fuel pump or clogged fuel filter, I can't remember which, causing a lean condition. Just a thought.

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post #4 of (permalink) Old 08-28-2000, 12:10 PM
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Re: engine knocking when under load..?

is it a "knocking" or a "pinging".. like a diesel? if it sounds like a diesel engine.. then your timing is a tad off..

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post #5 of (permalink) Old 08-28-2000, 01:55 PM Thread Starter
 
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Re: engine knocking when under load..?

nycjeep88...if it were a rod, dont you think I would hear it all the time?

jeepgod...it is that diesel type sound...timing is the first thing I suspected also. I advanced the timing quite a bit when I noticed it the first time...I initially set it at 8 degrees, now its around 12...how far can/should I go with it?

78 CJ5 w/360
"measure it with a micrometer, mark it with chalk, and cut it with an axe"
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post #6 of (permalink) Old 08-28-2000, 02:19 PM
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Re: engine knocking when under load..?

Wouldnt a lean condition cause detonation? You generally dont hear detonation. This isnt valve tick is it? My valves used to tick a little, that was fixed by switching to fully synthetic oil. Just a thought.

MattYJ
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post #7 of (permalink) Old 08-28-2000, 02:52 PM
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Re: engine knocking when under load..?

It might be a rod knock. I have the same problem with my 225 V6. I will start the engine. It will knock and then quiet down, then when i drive the knocking will get louder over 2000 rpms. I checked everything. Some of my friends thinks it is a loose wrist pin, but i don't know. I just kind of ignore the sound now. it has been doing it for at least three years now. It runs strong, there are no shavings, pressure is good, and onlt sometimes it will smoke when started, but i think it is carbon burn off. Well one of these days i will pull the motor and fix it, hopefully it is just the wrist pin [img]/wwwthreads_images/icons/smile.gif[/img]

Dan Stewart 1963 CJ5 "Caloosa Jeepers" member

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post #8 of (permalink) Old 08-28-2000, 04:12 PM Thread Starter
 
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Re: engine knocking when under load..?

Its definately not valve ticking...I recognize that noise. The part that confuses me is that it only does it under load(as I described earlier) and when the engine is hot. The engine still runs strong with good pressures.

78 CJ5 w/360
"measure it with a micrometer, mark it with chalk, and cut it with an axe"
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post #9 of (permalink) Old 08-28-2000, 07:52 PM
 
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Re: engine knocking when under load..?

if your runnning an AMC360 at 12 BTDC itll knock unless youve got really good gas and all of your EGR is working properly.

retard it until it doesnt knock under load, youll destroy the ehgine to keep running it that way.

it most likely happens after warmup because the cto vac switches redirect the flow of vac to and from teh egr at different tempetures.

you can try going thru the vac system and making sure the EGR is good, but most likely you will still not be able to run that advanceed on pump gas.



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post #10 of (permalink) Old 08-29-2000, 07:22 AM Thread Starter
 
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Re: engine knocking when under load..?

OK...OJ, I will move it a couple more degrees at a time until it is gone. But how far can I go? and aren't I tradeing off HP every time I move it further out?

78 CJ5 w/360
"measure it with a micrometer, mark it with chalk, and cut it with an axe"
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