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Unread 08-30-2014, 10:58 PM   #1
Red280
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New guy with a engine misfire question.

Hi everybody! As you can see i'm new around here and wanted to introduce my self. I just got my 1st jeep, although I've been tinkering with cars and bikes just about all my life.

Two weeks ago a '85 CJ7 pretty much just dropped into my life. A good friend of mine has been having some health problems and asked if i wanted his Jeep. He's owned it since new and drove it through college but parked it about '94 in a field in west Texas. About two years ago, he got the urge to get it going again and spent a bunch of money on it. I'd always drive it around and tinker with it when I was at his house, and I guess he got the idea I liked it, and thought it would have a good home here. Got the title in the mail today so it's all legal...Now I just have to make it run right...

Ever since he got it going it's idled rough. Once I got it home and started tuning it up, it became obvious that is was missing on one cylinder all the time. (#4) Did a compression check with good numbers across the board - about 165# average. Checked for spark and #4 is firing as it should.

Finally figured out that the valves aren't operating correctly, pulled the head and confirmed that the exhaust valve for #4 is barely moving up and down. The rocker arm is tight with no slack. It's not making any noticeable ticking noises.
At first I thought the lifter was collapsed, but not i'm thinking that the camshaft lobe may be wiped out.

I've read all the threads I could find on lifters and such... Any ideas?

THANKS!!!

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Unread 08-31-2014, 12:56 PM   #2
RenoF250
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Congrats on the new Jeep, hopefully your buddies health improves.

Sounds like a wiped cam lobe to me. Even if it is a lifter you cannot get it out without pulling the head. I think it is time for a new cam. You should be able to replace it in a day. Make sure you use some good break-in lube and oil so the new cam does not do the same.
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Unread 08-31-2014, 01:35 PM   #3
LumpyGrits
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Did you ck for bent push rod?
LG
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Unread 08-31-2014, 06:36 PM   #4
RenoF250
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Quote:
Originally Posted by LumpyGrits View Post
Did you ck for bent push rod?
LG
The rocker arm would go loose with a bent pushrod.
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Unread 08-31-2014, 06:51 PM   #5
Red280
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Thanks for the response ya'll. I'm pretty sure it's the cam too.

I wonder if these modern oils with little to no zink caused it to eat a cam lobe... I'm going tear into it tomorrow or tuesday and see whats up. Then engine has < 60k on it, so i hope it wouldn't need new cam bearings. If it does, do those have to be pressed in by a machine shop?

Thanks.
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Unread 08-31-2014, 07:19 PM   #6
RenoF250
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Quote:
Originally Posted by Red280 View Post
Thanks for the response ya'll. I'm pretty sure it's the cam too.

I wonder if these modern oils with little to no zink caused it to eat a cam lobe... I'm going tear into it tomorrow or tuesday and see whats up. Then engine has < 60k on it, so i hope it wouldn't need new cam bearings. If it does, do those have to be pressed in by a machine shop?

Thanks.
Many are convinced the lack of ZDDP is bad for the cam. I am not 100% convinced but I did use Lucas break-in oil with ZDDP just in case.

You need a bearing install tool so they go in straight, you might be able to rent one but I suspect your bearings are fine. I think I would change the chain anyway.

I used a Crower cam and it came with JoeGibbs assembly lube so I used that on the lobes and Lucas assembly lube everywhere else.

I used Crower camsaver lifters because they have a flat spot that lets them spray oil on the cam. I think the problem with these cams is poor oiling more than the oil itself. People with flat tappets in chevys do not seem to worry about ZDDPl but in a V8 all of the topside oil drains onto the cam. In the 258 it only gets what is slung off the crank, sprayed out of the cam bearings and squeezed past the lifters.

I was a little concerned the lifters would lower oil pressure but I have 70 psi cold, 60 hot, and 30 psi at idle hot.
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Unread 08-31-2014, 09:23 PM   #7
LumpyGrits
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I have 119+K miles on my almost 30 yr old 258.
Run only Castrol 20W50. Other than reseal the valve cover-Never had any engine issues.
LG
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Unread 09-01-2014, 06:34 AM   #8
Matt1981CJ7
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I had the same exact symptoms...misfiring in one cylinder, spark and fuel were fine.

Below is what I found when I removed the valve cover. Here's hoping your problem is a similar easy fix.

Matt
rockerfailure.jpg

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Unread 09-01-2014, 08:22 AM   #9
Red280
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Wow, I've never seen a pushrod wear through a rocker before. I hope it's something that easy. When I first figured the valve wasn't opening correctly, it was late and the shop was pretty dark. When i get home form work today I'll check it out!
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Unread 09-02-2014, 03:47 PM   #10
Red280
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Checked the rockers out yesterday. Unfortunately the push rod didn't come through the rocker.
I'm goint to start pulling the head and see what I find in a day or two.

Thanks for the info and advice. I'll let y'all know what I find out.
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Unread 09-06-2014, 07:25 PM   #11
Red280
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Well, I've had a few days to tear into it all. The cam lobe for the #4 exhaust valve is worn down to a nub. I mean it's almost round. The lifter is also scooped out pretty good. I've never seen a cam do this. Best I can figure it was probably a metallurgical defect with the cam. If it was a zink problem wouldn't it effect the other lobes as well??? Whatever, at least i know whats wrong and can fix it.

Based on some of what I read on this site, I ordered a a Crower cam, new lifters and a time set. My nylon timing gear was cracked and actually had a few chips in it.
It's kinda strange, some parts inside this engine are in great shape and others look like they have 200k on them. I guess sitting 20 years is rough on stuff...

But as you know these thing have a way of blowing up and the might as wells keep coming. After I pulled the head I saw that the cylinder walls were glazed pretty good so i decided to pull the engine. Then I though, well...if i have it out i should do the clutch - after all is was shuddering a little....

At this point I plan to pull the engine apart, measure the bores and of that checks out good, hone the cylinders and re-ring it. I did a basic valve job on it today and cleaned off a lot of gunk. I'm also going to paint the engine and engine bay while I've got it all out. After all, there won't be an easier time in the near future...

And so it begins!
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Unread 09-07-2014, 08:30 AM   #12
Mike Romain
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Ug. What would worry me is where did all the metal shavings go..... I am thinking all the oil passages now need flushing.
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Unread 09-12-2014, 08:06 PM   #13
RenoF250
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Quote:
Originally Posted by Mike Romain View Post
Ug. What would worry me is where did all the metal shavings go..... I am thinking all the oil passages now need flushing.
The oil filter. Unlikely what came off of the lifter was big enough to get stuck in a passage. Besides what runs off the cam goes into the pan, into the oil pump and then through the filter.

The lobes are surface hardened, apparently #4 was not done properly.
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Unread 10-15-2014, 06:55 PM   #14
Red280
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Pulled the engine down over the last few weeks. Thankfully didn't find any metal shavings. Did find a decent amount of goo in the bottom of the pan, some of which was metallic.

As suspected the #4 exhaust lobs was gone. No galling or chunks missing - just worn smooth down to a nub. In reasearching this issue I read an acticle by Crane Cams that bascially stated that it's unusual for a single lobe on a cam to fail due to a metallurgical issue. A cam is heat treated as a unit, so all the lobes should be the same hardness and therefore wear evenly. It also stated that sometimes a single lobe failure is due to a machining error or perhaps a bad lifter. But it went onto say that the most likely culprit is that the cam was out of position (thrust front to back) which would cause the lifter to ride towards an edge - rather than the center of the lobe. The lobes are cut with a slope that causes the lifter to rotate. Lifter in the wrong place = not rotating = not wearing properly = worn lobe and other lobe damages soon to follow.
Following this logic, #4 exhaust was just the first to fail.

Is this what really happened? Honestly, i'm not knowledgable enough to know. But i did notice that the cam sprocket thurst surface was worn compared to the new timing set I bought.

So, i've decided to just rebuild the engine.
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Unread 10-16-2014, 07:01 AM   #15
Matt1981CJ7
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I think improper thrust position would cause all the lobes and lifters to wear prematurely, not just one.

I'm guessing your #4 exhaust lifter was stuck in its bore.

Matt
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