91 Wagoneer 360 missing on 4cyls - Jeep Garage - Jeep Forum

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Old 12-01-2012, 10:31 PM
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91 Wagoneer 360 missing on 4cyls

Hello to all fellow Jeep fans out there, I'm new here tonight and hope there is someone that can lead me in the right direction on my Wagoneer cause I am stumped now!

I have a beautiful 91 Grand Wagoneer with the 360 and it currently has 132,000 miles on it now. I have had this one for a year now and it has been running fantastic all summer with no issues. Last Saturday we did an oil change, new belts, set timing, changed plugs (Autolite 65's) and just general tune up stuff to have it prepped for the winter months. When we started it back up we noticed what sounded like a small miss in the motor so we started checking everything we could think of and when we pulled the dist cap we found major amount of metallic dust stuck to the magnets and the rotor button had quite a bit of play so we went and got a new distributor, cap & rotor and installed them and when we fstarted it up, it did the same thing.

mileage has dropped from 16-18mpg to about 5mpg. It has a new set of wires on it as well. While it was running we started pulling plug wires from the cap one at a time to try and figure out which cyl wasn't firing and thats when we found 4 of them not firing at all. There is spark popping from the cap to the wire if I hold the wire close enough but when its removed completely it does not make any change in the running of the engine but if I pull the one next to it after I re-installed the first wire then it really starts lugging and wanting to stall unless I get the wire back on quick.

I started with the #1 cyl wire on the cap and it was firing, then the next wire going clockwise is #8 and it is not firing at the cyl, the next one fires, the next one does not, so basically every other wire on the cap is not firing at the cyl. I put my spark plug tester on it today and I'm showing fire at the plug end of the wires so I put an extra brand new autolite plug on the plug end of the wire so I could see if the actual plug is firing and it is which is leading me to think this may be an internal problem or a head problem but its just wierd that ive lost 2 cyls on each bank.

I also installed a new coil and the engine control box (not sure of the correct name) on the top of the drivers side fender in the engine compartment. I think I have pretty much anything in the electrical system related to spark and fire replaced with brand new parts and nothing has made a difference at all. It is still equiped with the motorcraft 2bbl carb and intake also.

Can anybody give me any other ideas of what to check or try? Ive got to get this truck running good again cause the wifes truck just lost the transmission 2 weeks ago and this is our only driver at the moment. I do have another Wagoneer that we have been in process of building for the last 2 years now and we are in process of doing paint and body work on her now but it does have the exact same motor set-up and it runs strong so I'm half tempted of just doing a quick motor swap if it is internal issues but really don't want to go thru that if I don't have too. We also pulled a compression check yesterday and I'm averaging 130lbs of compression on the dead cyls with only a few lbs difference between cyls so the engine seems pretty good from what I can tell unless it's a cam/lifter issue. I just don't know what else to check tho at this point.

I'm also confused on it because even tho i'm only running on 4cyls, she still has good acceleration, runs smooth at highway speeds, makes no knocking noises, but has become hard to start and runs like crap at idle. I truly welcome and appreciate any suggestions on next steps. If you need any other info then please let me know and I will get back pretty quick.

Thank you for input and reading the long post guys, I'm sorry it's so long but wanted to try and give as much info as possible.


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