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1996 XJ Misfire Problems

M

my1996xj

NAXJA Forum User
Location
Cleveland Ohio
First Off Hello to all, I am a old Jeep owner who has finally decided to purchase another one!!

I have a 1996 XJ 4.0, The head gasket blew about 2 weeks ago, I finally got everything replaced(new gaskets, plugs, wires, temp and oil sensor, therm). After all of this now the cat throws a code for multiple misfire and a cyl 4 misfire.

It is idleing rough, then runs fine up until about 45 mph, then goes rough again. It does seem to be blowing some gas out of the tailpipe as well.

Any ideas?? I am driving myself nuts and I really want to start driving this thing!!
 
Pull each plug wire individually to see if you can find a single cylinder that doesn't change the idle more. Do you have the old plug wires to try? Also, did you check the gap on the plugs? And what plugs did you install?
 
Last edited:
I used NGK Plugs, set the gap at .035. I do not have the old plug wires(of course I threw them out), but I will try pulling the plug wires. What should I look for when I pull the wire?
 
Well I don't have a problem with spark, so I checked fuel. Here's what i found:

When I pull the injector wires to cyl 4 and 6 it make no change in the way the car runs(still shitty)

Spark plug to 6 is blackend at the end! (2 days old)

When i pull the wires to any other injector is makes a BIG Difference!!

Should i assume I have a Valve problem in cyl 4 and 6??
 
It certainly sounds like you have injector problems on those two cylinders... what does the #4 plug look like?
Are you able to check compression or leak down test? Its odd that the injectors would suddenly fail after a head gasket replacement
 
The #4 plug looks normal, the one tool i don't have is a compression tester. It does seem really odd, the car ran perfect before the head gasket problem.
 
Switch the #6 injector to another cylinder and see if the problem moves.

It doesn't move, the injector is good.
 
Check compression to make sure the head gasket fixed your problem. Did you check the head for flatness and the valves for sealing while you had the head off? But you're possbly wasting time without validating physical sealing of cylinders with test of compression.
 
Well i swapped out the injectors and the problem doesn't move! It has give me 2 codes 0300 and 0304 for the misfires. It looks like I need to by a compression tester unless anyone else has any ideas??
 
Well, since you have spark and fuel the options aren't good. Its odd that it presents with a 0300 and a 0304 though. Could be a sensor though. Did you test the fuel pressure? I would suggest you do that as well, perhaps you have a mechanic that you use regularly that you could borrow the gauges from?
 
Many of the auto store chains rent or sell/rebuy tools like this. It is not expensive, but is kind of mandatory before you ever buy a vehicle that is not running perfectly. You can chase your tail on problems, but if you have a compression problem, all the electrical and fuel crap in the world won't help.
 
I don't know of any auto parts stores that rent gauges... they rent other tools such as pullers, ball joint presses, ect.. but nothing that has the potential to break or fall out of calibration like a gauge. It wouldn't hurt to check though.
 
Well, the compression is good on all cylinders??? Still running rough and throwing misfire codes!!

When i pull the connections to fuel injector 4 and 6 there is still no change in anything???

I tried swapping out the injectors and they are good

What now??

Shotgun to the Jeep??
 
my1996xj said:
If I pull any of the other connections the car idle drops and it wants to start stalling.
Click to expand...

So you have 1, 2, 3, and 5 but no 4, 6. You swapped the injectors around, no difference, so the injectors are not the problem.

That leaves the electrical to the injectors, or the cap/wire/spark plugs.
 
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