The Dreaded Cylinder 2 Misfire

[T3STERS]

Hello all,

Long time reader, first time poster.
I have had a cylinder 2 misfire since I bought my TJ about 6 months ago.
A few details
- 160k miles
- Idles around 800rpm
- About 10.5mpg (4:10s, 33's, Dana 44 rear) Not sure if this helps much but what the heck.
- Replaced Coil
- Replaced spark plugs with some that Jerry recommended on these forums-- Gapped correctly
- Replaced Fuel injector on cylinder 2
- CEL goes away along with misfire while running seafoam in the tank (started with 1oz/gal now at .5oz/gal)
- After 2 cans of seafoam/gas misfire did not return for about 2 months, I tallied it up as something in the fuel system but it has now returned.

I plan to check compression tonight but I am not expecting to find too much since the additive seems to correct the issue.

Any other advice?

 

[T3STERS]

@Jerry Bransford From what I can see, you're the guy with an infinite amount of advice.

Please help. lol

 

[CodaMan]

There's an entire thread in the how-to section on troubleshooting a single cylinder misfire.

 

[CodaMan]

https://wranglertjforum.com/threads...the-dreaded-misfire-and-how-i-solved-it.4212/

 

[T3STERS]

https://wranglertjforum.com/threads...the-dreaded-misfire-and-how-i-solved-it.4212/

Thanks CodaMan!
I’ll do some more checking but what differs for me is that it will run with additive; is there any reasonable excuse for that?

 

[Chris]

Check your compression and do a leak down test. It's possible you have a cracked cylinder head as well.

 

[CodaMan]

Thanks CodaMan!
I’ll do some more checking but what differs for me is that it will run with additive; is there any reasonable excuse for that?

No! and forget about the additives and troubleshoot the misfire.

 

[T3STERS]

Will do a compression test tonight. Thanks again.

 

[T3STERS]

The plot thickens
1-135 psi
2-145 psi
3-160 psi
4-150 psi
5-125 psi
6-125 psi

 

[Claytone]

Time for a leak down test.

 

[T3STERS]

While double checking for intake leaks I noticed a bolt missing on the intake manifold by cylinder 1. I found it miraculously.. I sprayed carb cleaner with it running but didn’t see a difference,
I’m sure this is somehow related though.

looks like manifold is broken as well.

 

[MrMark52]

Welcome fellow Texan!

I agree with @Claytone - you probably need to do a cylinder leak down test. You should be able to borrow one from AutoZone or OReillys. I would also recommended that you borrow a fuel pressure gauge at the same time to test fuel pressure. 160k is a lot of miles for a fuel pump/regulator assembly.

Procedure for doing a leak down test is in the FSM for my ‘03.

How do you know that the misfire is always cylinder 2?

And I’m not certain that the missing manifold bolt on #1 would cause issues with #2 (seems issues would be more prevalent with #1).

Is it possible that the head has been pulled before trying to investigate the same misfire issue, and the bolt was either not replaced or broken off? Look for signs of a sloppy head replacement (broken tie-wraps, hoses not routed and properly clamped, etc.).