Off-Road Forums & Discussion Groups

Off-Road Forums & Discussion Groups (
-   Jeep-Short Wheelbase (
-   -   Knock Knock (

unhumen 09-10-2001 12:34 AM

Knock Knock
If it is a joke it is on me,cause I pulled my tranny for nothing.The knocking noise that I assumed was coming from my transmission input or countershaft was in reality coming from my engine and as near as I can figure it is an Ignition knock.
So today I pulled out the Tac. the timing light and the vacume gauge and started testing ,I have already eliminated the EGR.and the vacume advance is working,tested with a hand vacume pump.So the symptoms are,
it does not knock when the engine is first started and does not start until the temperature is about 145* ,that is when the CTO switches from manifold to ported vacume ,and appx. 1000 RPM .I have detected a slight leak in the accelerator shaft of the Infamous Carter BBD,with the spray carb cleaner method,and it does not drop completely back to 750 RPM unless forced by hand.that is how I know it starts at 1000RPM cause when I force it back the knock stops.also when it does drop back to 750 RPM on its own as I accelerate and let the clutch out it starts and then stops when fully accelerated.this is why I thought it was in the trans.the trans was the last big thing I did thus I figured I screwed something up when I reassembled it.Also my charcoal cannister signal is on ported vacume so I am wondering if it is shot and between the leaking accelerator shaft and possible leaking charcoal cannister it may be causing a lean mixture at 1000 rpm causing the knock
anyone care to postulate a further hypothisis on this matter ?

Learn to let go of what does not serve you ,but forces you to serve it
why does everyone ask if I am gonna paint it ?

Jaffer 09-10-2001 07:23 AM

Re: Knock Knock
Hummm ...
Sounds like a connecting rod knock.
That could spell bad news. [img]/wwwthreads_images/icons/frown.gif[/img]
First of all check your ignition timing...
Can you hear a continuous knock with the engine warmed up and in neutral buy reving the engine at a sustained 2000 RPM? .... sympton of a bad rod.
Or does it knock only under load? ... sympton of detonation (ping]
Next check you spark plugs. If they are pretty white colored it could spell ping (lean mixture)
Also, a stethescope or long screwdriver to your ear with the end placed on the block under the spark plugs will allow you to hear the problem better.
If you rev to 1000/1500 RPM and hear a contiuuous knocking it will probably mean you have a rod bearing or wrist pin going out.


unhumen 09-10-2001 08:24 AM

Re: Knock Knock
That was my first thought ,bearing or wristpin ,however the only place I hear it is either in the oilpan or at the very bottom of (flat part ) of my bellhousing,with a stethascope.I will try the block under the plugs ,but before I tear anything apart again I am making sure of what it is.that is why I am testing everything that can cause a knock first.The plugs when I checked them last were on the dark side but what I am going to do is run it at about 1000 RPM for a while turn it off and check them to see if they are looking lean.
I am planning on dumping the BBD anyhow possibly in favor or a rochester or MC2100,as soon as I figure this out.

Learn to let go of what does not serve you ,but forces you to serve it
why does everyone ask if I am gonna paint it ?

All times are GMT -5. The time now is 04:52 AM.

Powered by vBulletin® Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.

User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright 1994-2009, VerticalScope Inc. // Off Road forums & discussion groups sitemap
side by side | atv | dirtbike | snowmobile | sandsport | competition | land use | Jeep | Toyota | Ford | GM

For the best viewing experience please update your browser to Google Chrome