Constant Misfire on Cylinder 1 in 1997 ZJ 4.0

[Mattman99]

I have a 97 ZJ that is constantly misfiring on cylinder #1. I hqve done plugs, wires, distributor cap and rotor, injectors, and a compression check. I got 135psi of compression in cylinder #1 and 153psi in cylinder #2 just for a comparison. Any thoughts?

[4.3L XJ]

Is it using engine coolant?

[Mattman99]

No, it is not using coolant as far as I have noticed. I make sure to keep all of my fluids where they should be since I am going to school for automechanics.

[Mattman99]

I have been trying to fix the misfire for almost a month now and I even bought valve springs that I have not put in yet.

[4.3L XJ]

I was wondering if you had a small head gasket leak. Doesn't take much for a miss at idle. Does it smooth out under power or at higher revs? Have you thought of replacing that injector?

[Mattman99]

It smooths out a little bit when under load, but anything over 1500 rpms (while in park) and the valve train starts to chatter or 2000 rpms while driving before the valve train starts to chatter. I recently replaced the injector on cylinder 1 and it didn't do much. Both my dad and I are wondering if doing the other 5 injectors would help.

[Mattman99]

I'm curious if I may have a small head gasket leak because my coolant is black and it was fluorescent green a few days ago. So its almost like if my oil is getting into the coolant. I don't have any good way of seeing into the cylinder since I know that cylinders that are nice and shiny while the others are all covered in carbon are ones that had coolant leaking into them.

[4.3L XJ]

A radiator shop will analyze your coolant for exhaust gasses

[Ralph77]

Originally Posted by 4.3L XJ

A radiator shop will analyze your coolant for exhaust gasses

You can rent a block tester at some auto parts stores. But I think you have to buy the fluid. Which will be way more then you need for one test.

I just went and bought one. I wanted to check it out hot. So my idea was to use my Lisle funnel. This would let me keep the radiator cap off and not having coolant going everywhere. When I got her nice and hot I used the stopper to remove the funnel and saved the fluid in a jug. Then I sucked more fluid out of the radiator. Cause you don't want any coolant going up it to the block tester when you use it. All went well. See the first shot. My buddy was hanging out with me and says put it by the tail pipe and see what happens. See the second shot. LOL.

[Mattman99]

I don't have any radiator shops near me that I know of, but the small head gasket leak is the only thing that would make sense on why it has a misfire in cylinder #1 after doing all the ignition components and a new injector on that cylinder.

[Gluckmysock]

Have you pulled the valve cover to look for any broken springs or stuck valves?
Also, how many miles?
The lifters are hydraulic and I have heard of the cam wearing holes in the bottom.

[Mattman99]

I have pulled the valve cover a few times and nothing is broken or stuck and it has just over 178k miles. I am planning on pulling the head this weekend and doing the head gasket, lifters, and valve springs. I had a coworker who does mostly engine repair look at my coolant and he said that there is definitely oil in it. I will let you guys know what I find when I pull the head this weekend if I can get the time.

[4.3L XJ]

That is the direction I was heading with my questions

[Mattman99]

4.3L XJ, I guess I kinda overlooked the whole head gasket thing, but then when I was thinking about the whole coolant thing I thought that it was very peculiar that my coolant just became black like there is motor oil in it and that's when I realized that maybe you were pointing me in the right direction and I was just being ignorant about the whole thing since I have done almost everything.

[4.3L XJ]

Glad you are heading in the right direction now That is what we are here for