SOLVED! Jeep Wrangler Misfire is over - a hard lesson learned - Can't believe the cause!

Be sure to check out all 4 videos in this series to watch me diagnose this misfire issue:

Finally figured out the jeep tj cylinder 3 misfire issue. A hard lesson learned - here is the final video. Glad she is running smoothly now. How this helps others in the future! We checked everything from fuel injectors, to the wiring, to the compression, a leak down test, vacuum test. Many of the parts and testing supplies we purchased either from amazon or rented from local big box stores. We were even thinking this could be a heat soak issue, but the real issue were the spark plugs. So we replaced the plugs with some high quality iridium and this issue is no longer active. Glad to be done with it!

[falseshepherd]

You saved me a world of pain brother. I have a new rebuild of my 4.0L, and the store sold me the wrong spark plugs. Jeep ran fine at higher revs, but rough at idle. Gave me a miss-fire code. I replaced the already brand new (wrong) spark plugs with a new set of correct plugs, and all good! Thanks again.

[mra]

Nice Video. I am a career mechanic. That said, in diagnosis always remember that hesitation and miss under load is usually due to a weak ignition. Plugs first, then spark plug wires. We had 4.3 V-6 motors in a lot of our fleet at UPS. After a couple years they started throwing various codes. When tracking it down, we had done spark plugs, cap & rotor, and still had codes throwing. Plug wires looked like new. Guess what, put a set of wires on and the motors ran perfect. Lesson learned. Take care of the basics first.

[curtiswhite]

I’ve seen a few of your videos, but this is what made me subscribe. I recently changed my spark plugs to double platinum Bosch plugs on my 4.0L, and it sounded great in the garage. When I took it out, got a cyl 1 misfire. Shortly later, cyl 5 misfire. Not even 100 miles on the new plugs. I thought the spark plugs causes a chain effect of other parts to go wrong. I had my rockauto shopping cart LOADED, but wasn’t 100% confident of it all. I just so happen to still have my old champion plugs, put them back in and it all went away lol. Well, no more Bosch plugs for me. Thanks for the tip, saved me hundreds of dollars and hours of work.

[zodiac]

I start with the same problem!! Very low idle, stalling, shuts down when stop or when engage clutch at first it do when warm, now when jeep is cold too. I will try with the sparks first! Thanks for all your videos! Really appreciated!

[thehatefull]

First time I ever did a tune-up on my 4.0 I went and bought brand new iridium cuz that's what AutoZone said I should use. Ran fine until you get up around four grand and it would start skipping. Took the old spark plug that I just pulled out of them back up there and told him to give me the exact ones which were coppers pulled their Iridiums out put the coppers back in and it ran fine.

[erikherring]

This misfire code are caused by the Jeep Gods!! They know it will keep us all in constant communication combing through forums and YouTube videos. It’s bigger than us. 🤣

[bohuslavhumplik]

Jeep....Making Mechanics out of Drivers since 1942!

[frederickdupont]

I had the same problem, and I also bought, part after part trying to fix the issue. Searching once again for a solution, i came across this very video. Wham-Bam-Bing-Boom-Bada-Bop, and the problem is fixed. I was using Bosch Platinum before I switched to the same ones in this video. Oh on a totally different note. I am selling six slightly use (2 weeks) Bosch Platinum spark plugs and still in the unoriginal box

[MadDogXJ]

Yay!! Wow what a trip.. Im happy you found the issue. And shared your triumphs🎉🎈🎊🎆

[MattBrownbill]

I have just put a set of those iridium plugs in my ZJ, they were recommended as mine is converted to LPG/CNG. Looks like I made a good choice then!

[jamesrodgers]

I have a 2001 TJ with the 4.0 L six-cylinder. I had a number three misfire code. Replacing the spark plugs cleared the problem. I’m considering putting the MSD Coil pack rail in just for good measure though.

[the-bulb]

I’m glad it worked out for you. But these new Jeep you have to remove the complete top end just to have access the spark plugs it’s a 4-6 hr job. I still do t even know if it will work.

[sharplessguy]

At 3:57 I paused the video and zoomed in on the top ceramics of your plugs... I have seen arcing before where the coil pack arcs across the top of the plug due to contaminate like carbon or oil/water forms a path for current. At least one of your plugs looked like the ceramic between the coil and the lower metal base was fairly dirty/contaminated....

[tomhubbard]

I know this is an old video but... The 4.0 don't like fancy spark plugs IE iridium etc. The forums pretty much all say to just use the good old simple Champion standard plug. They go and go and are cheap. The coil on plug can have connection issues in the connectors. Check ALL connections before firing the parts cannon LOL... I spent "A LOT" of money on my Duramax to FINALLY find a bad connection in the AC system that was crippling the truck. No NOT the same thing but, , , connections connections connections!

[destroytheilluminati]

had a 95 jeep wrangler that i had done plugs wires and cap and rotor, shorty after i did that it developed a misfire, being that everything was new tune up wise i started to suspect injector was failing, while running i could pull the connector off and isolate the miss, replaced injector to no avail. so i pulled the plugs to take a look at them and i discovered the porcelain on the plugs were all red (they were ac equivalents of the champions they didnt have at the time) replaced with correct champions, miss went away. AC plugs are junk

[Jeff-wuwn]

i got the E3 plugs and they are so awsome !!! i noticed a big difference in idle, millage and over all performance well worth the extra few dollars!!

[charleswright]

I think someone may have mentioned it, but if you swap out a plug for another, and you still have same problem, your plug wire may be suspect.

[Nobamaable]

These tractor engines do NOT like iridium plugs... use the recommended OEM plugs and you will be fine.

[libra]

YouTube mechanic here, but I've got limited experience with other relevant theories. Maybe it's possible it's your ignition rail? New plugs might handle the lower voltages better or the dielectric grease is allowing better continuity of the voltage to the plugs. That's my theory on why it initially migrated with cylinder 3 but went away after replacing.

[bkpickell]

My YJ has the opposite problem as yours. It idles and accelerates very smoothly. When I get up to speed and driving at around 2000 RPM it starts missing. Gear doesn't matter. Will not miss in neutral. I've thrown all sorts of parts at it: plugs, wires, coil, cap, roror, distributer, O2 sensors, Throttle body, fuel filter. I'm kind of stuck now.