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Unread 10-09-2013, 06:00 PM   #1
Alex77cj7
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1977 CJ7 
 
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Need help asap. Misfiring on one cylinder

Okay I need to find a answer for this ASAP. I was driving down a street in town and punched it. I don't remember what rpm I was at but all of a sudden I heard a pop then my jeep started running like dookie. Fixed my exhaust leaks hoping that it would fix the problem since after the pop the exhaust leak was much worse on the passenger side. Just finished checking my headers with a temp gauge and the second cylinder on the passenger side is now misfiring. I checked the wire with my timing light and it shows spark and I swapped spark plugs with another cylinder and it still isn't firing. There's no odd noises coming from the engine and the misfire really isn't that violent. It's almost like its firing sometimes.

Specs:
Amc 304 slightly bored with a summit racing cam. Edelbrock performer intake and Holley 4 barrel carb. All Msd ignition with a mad 6al. Has team rush upgrade too. Long tube headers. Anything else that I missed please feel free to ask.

Thanks,
Alex

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Unread 10-09-2013, 06:01 PM   #2
MoneypitCJ5
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Check compression - sounds like it smoked a valve
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Unread 10-09-2013, 06:11 PM   #3
Alex77cj7
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Quote:
Originally Posted by MoneypitCJ5
Check compression - sounds like it smoked a valve
Ill do that when I get home. If it smoked a valve how hard is it to fix and how long should it take?
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Unread 10-09-2013, 06:21 PM   #4
MoneypitCJ5
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You have to pull the head and remove the valve spring and retainers.
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Unread 10-09-2013, 06:26 PM   #5
MoneypitCJ5
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If the compression test shows low or zero compression, and you have an air compressor there's something else you can do to check valve sealing.

Pull the valve cover and remove both rocker arms on the cylinder in question.

Take the hose from your compression tester and take the check valve out, then screw it in and hook it up to shop air.

Then if you hear air moving, listen at the carb, exhaust pipe, and oil fill.

If air is coming out the carb, it's an intake valve
If it's coming out of the exhaust it's an exhaust valve
If it comes out of the oil fill, you burnt the rings or piston and will need a rebuild.
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1977 CJ5 304, 3MT - under construction
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Unread 10-09-2013, 06:39 PM   #6
Alex77cj7
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Quote:
Originally Posted by MoneypitCJ5
If the compression test shows low or zero compression, and you have an air compressor there's something else you can do to check valve sealing. Pull the valve cover and remove both rocker arms on the cylinder in question. Take the hose from your compression tester and take the check valve out, then screw it in and hook it up to shop air. Then if you hear air moving, listen at the carb, exhaust pipe, and oil fill. If air is coming out the carb, it's an intake valve If it's coming out of the exhaust it's an exhaust valve If it comes out of the oil fill, you burnt the rings or piston and will need a rebuild.
Thank you so much. Would it be worth just changing the valves or better just to order new performance heads and swap them in?
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Unread 10-09-2013, 06:42 PM   #7
Alex77cj7
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Also, i don't know if it would help or not but it used to misfire and smoke a little when the engine was cold for like a minute or so. The problem went away for a few months and just came back about a month ago. And now this. It's still drivable but it gets rough when the jeep
Is under load. Like taking off or accelerating in 4th gear.
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Unread 10-09-2013, 06:59 PM   #8
CJ5_Fan
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Start simple, verify you don't have a bad wire arcing against the block or some other part of the motor like the heat riser tube or the air pump piping. It can be intermittent and will cause a cylinder to drop out when it happens.
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Unread 10-09-2013, 07:05 PM   #9
Alex77cj7
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Quote:
Originally Posted by CJ5_Fan
Start simple, verify you don't have a bad wire arcing against the block or some other part of the motor like the heat riser tube or the air pump piping. It can be intermittent and will cause a cylinder to drop out when it happens.
The wire shouldn't be arcing. They are all performance wires and are routed away from stuff that they could arc on. And I don't have any emissions stuff on my engine. So air pump pipe is out.
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Unread 10-09-2013, 08:25 PM   #10
Alex77cj7
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Also is there anything else Y'all recommend changing out while I have it apart?
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Unread 10-10-2013, 06:32 AM   #11
MoneypitCJ5
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I'm a "don't fix it if it ain't broke" kinda guy. It sounds like you've got a pretty good setup as it is.
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Unread 10-10-2013, 08:12 AM   #12
Alex77cj7
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Quote:
Originally Posted by MoneypitCJ5
I'm a "don't fix it if it ain't broke" kinda guy. It sounds like you've got a pretty good setup as it is.
Thanks. One of my friends has a new crate 304 that he would sell me for $600. I might buy that and put all the same mods I have on this one on it but maybe a bigger cam and drop it in my jeep instead of fixing this one. And then that leaves me an extra engine for parts for my jeep and my dads truck.
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Unread 10-10-2013, 08:21 AM   #13
MoneypitCJ5
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I wish I had a friend like that! Mine runs pretty good, considering it sat for 15 years before I got it. I know its days are numbered though.

I hope to swing a 360 swap at some point
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Unread 10-10-2013, 06:29 PM   #14
yahwhy
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Don't miscount those fancy dancy plug wires you got, say you just fixed exhaust leak? hedder gaskets?
If not oh well, but I have a sbc in mine with the hedman conversion hedders and seem to be frying # 5 alot, and I get that pop you speak of.
And I know its time to fix a wire.
Might not be an issue for you but it don't cost nothin to check.
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Unread 10-10-2013, 07:50 PM   #15
LumpyGrits
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Pull a valve cover and ck for a 'popped'/bent p'rod or rocker.
LG
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