87 YJ 4.2L Conundrum - Page 2 - JeepForum.com

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post #16 of 26 Old 01-19-2014, 02:25 PM
blaylock6502
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Although not that likely from your explanation the only thing I can think of is carbon. When carbon deposits become heavy enough they can soak up enough fuel to starve a cylinder. This would also explain possibly why it is worse when cold as much more fuel is required on a cold start.

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post #17 of 26 Old 01-19-2014, 03:00 PM
YJasaurusrex
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did you ever check the plug wires or the distributer cap, spark plugs ? Try using one of those spark checkers, they have an inductive one that you don't have to put in line with the plug wire and see if you can determine which cylinder is the culprit or maybe it's multiple ones. Vac leaks on a YJ... those are crazy to find being as there is enough vac line on them to circle the earth twice.
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post #18 of 26 Old 01-19-2014, 03:22 PM
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Quote:
Originally Posted by YJasaurusrex View Post
Vac leaks on a YJ... those are crazy to find being as there is enough vac line on them to circle the earth twice.
Lol so true.

That would have to be a hell of a lot of carbon... but it's possible.

When all else fails... SEAFOAM! (then new plugs)
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post #19 of 26 Old 01-20-2014, 09:29 PM
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Pull one spark plug at a time and start it up if it gets worst that isn't the cylinder. Do that for each plug. When a pulled plug doesn't make it run worse than it usually does that it the cylinder that is causing the problem. It could be a bad spark plug or wire, or cap. Or, it could be internal.

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post #20 of 26 Old 01-21-2014, 07:26 AM
Old4X
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If you are going the "pull a plug" route, ground the loose wire. You will ruin ignition components if you don't.

418 miles on 19 gallons of gas. Can't beat the BBD !
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post #21 of 26 Old 02-05-2014, 10:18 AM Thread Starter
mefish
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Okay figured it out. Pulled the valve cover (why do they have to make it so hard on these motors?) and rotated the engine to observe the top end functions. Two valves (in my weak cylinders as observed while pulling plug wires idling) the exhaust on 2 and intake on 5 only moved about a half or less of the other rockers. So this prompted a deep dive to find the miss. Pulled the head, lifters and cam. Oh my there was a problem. In the pics below you can see the worn off cams on the camshaft. Needless to say the head is being gone thru and I have ordered the cam and lifters for replacement. Crazy wear but the machine shop swears it is due to lack of zinc in the oils now and he also swears that the additives don't work as the newer oils keep the zinc in suspension. I don't know about that but I guess I should have taken the head dive when I first got this rig but I never noticed the top end not functioning correctly when rotating the motor. Lesson learned since I already did a new timing set and was 3/4s of the way to pulling the cam at that time.
Oh well.
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post #22 of 26 Old 02-05-2014, 10:55 AM
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Wow! Thanks for sharing and good work!
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post #23 of 26 Old 02-05-2014, 12:54 PM
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Rotella still has some zinc

418 miles on 19 gallons of gas. Can't beat the BBD !
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post #24 of 26 Old 02-05-2014, 02:43 PM
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I wonder if this engine which probably has a ton of miles on it had some block oil passages?

How regularly was the oil/filter changed over the decades? Dirty oil causes the most damage to engines. Oil with suspended particulates in it would be more accurately call slurry. Slurry is often used as a cutting tool.

If zinc was the main issue then wouldn't the wear would be fairly even on most if not all of the lobes?

For you it isn't relevant since the cam is toast and needs to be replaced. But oil flow,...or a lack of oil flow, or block oil passageways might be a more accurate cause.

Again it doesn't make much difference to you since the cam is toast no matter what happened.

Do you know what was good about the good old days? I wasn't good, And I wasn't old!

Senators and Congressman should wear uniforms like NASCAR drivers so we could identify their corporate sponsors....
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post #25 of 26 Old 02-06-2014, 07:30 AM
vadslram
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Garage
[quote=fishadventure;19545433]
Quote:
Originally Posted by CB10101 View Post
Instead of using a file on the carb adapters, lay a sheet of 60 grit on the cement floor in the gargage and deck them that way. Easier to make sure you are level across the entire surface.../QUOTE]

I do something like this but a little more precise. I have a used tempered glass display shelf 3/8" thick by 14"x36" I picked up from a store remodel scrap heap. It is PERFECT for things like this.

I use rolls of adhesive-backed sandpaper which I stick on the flat glass plate or I tape 8-1/2"x11" sheets to it depending on what I need to do. When parts are scuffed on this setup in a rotating figure eight pattern you get a machine-quality truly flat surface. I mostly use 180 grit but 120 is a close second. Any plate glass will do but the shelf was perfect. Before I had the easily moved glass I had a piece of broken polished granite countertop which was nearly surface plate flat but weighed like 250#

Just thought I would pass that along...it's been very useful for me.
Sounds like you are prepping a fiber optic connection.

I'm not feeling the gasket leak theory. You sprayed carb cleaner around with no change and the needle fluctuates (bounces?)
To me that reaks of single valve problem. Have you checked the valve clearances when closed? If one valve is hanging open/closing late you will get a bounce on the vacum gauge.
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post #26 of 26 Old 02-06-2014, 08:14 AM
Mark05059
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[quote=vadslram;20102562]
Quote:
Originally Posted by fishadventure View Post

Sounds like you are prepping a fiber optic connection.

I'm not feeling the gasket leak theory. You sprayed carb cleaner around with no change and the needle fluctuates (bounces?)
To me that reaks of single valve problem. Have you checked the valve clearances when closed? If one valve is hanging open/closing late you will get a bounce on the vacum gauge.
your late to the party but totally correct.... The cam lobes are worn off making one cyl not open correctly

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1989 Wrangler Black Bone Stock 2.5l 5spd
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