Warren Dwight Page

Trying to figure out what this issue is.
I replaced the plugs, new coil pack. Yes I have the foil heat shield for injectors.

I guess replace the injectors?? Or what else could it be?

XJwonders

Inspect the wiring harness that feed the injectors for any rubbing or chafing

thebyus

I had the same problem when I first picked mine up. After searching the threads, the overwhelming consensus was that it was probably the spark plugs. I pulled the old ones - turns out the PO had installed Bosch platinum. For some reason, the cylinder 3 misfires on these. I replaced them with NGK copper plugs and haven't had the issue since -

Check out this thread

It might NOT be the plugs, but it is worth $10 to find out, before you start replacing injectors!

Warren Dwight Page

Yeah, my buddy suggested different plugs. I pulled them out and they looked fine. I forget now what kind they are.
Your right, for 10 bucks it doesn't hurt.

XJwonders

BlvdKreeper

I have something similar except its a p0302 code.

Warren Dwight Page

What is p0302 code???

Heap'99

Cylinder 2 misfire.

winston427

The 00-01 4.0s have a problem with the very back bolt on the intake/exhaust manifold backing out. It doesn't come out far, just enough to cause a leak in the gasket. When letting off of the accelerator it sucks air in and causes a misfire code. The tell tale symptom is a whistle when letting off of the gas.

My 01 was throwing random misfire codes constantly. I changed the plugs, wires, and coil pack twice. All with top quality parts and keep getting codes. Changed the injectors with no change. Finally after months of research I heard about the bolt issue. Tightened the bolt to the proper torque and it stopped for a while but the gasket had warped and would eventually repeat the issue. Finally got around to replacing the gasket and never had the problem again.

thebyus

Good information to know. Wonder if my issue was really a bolt problem. Haven't had the problem come back, but if it does, I will have to keep this in mind.

Warren Dwight Page

Well, I'll be dammed!
Yes, that whistle just started a couple days ago!
I thought it had something to do with the intake. So I went through and tightened the clamps.
That just started though. A couple days ago. I have had the misfire code for a while.

winston427

Another issue mine had to go along with the whistle and the misfire codes was a heat soak vapor lock. After driving the Jeep for 30 minutes or more if I parked it for about 10-15 minutes the exhaust heat would migrate up into the injectors and vapor lock them. When I restarted the Jeep it would run fine for just a few minutes and then fall flat on its ****, as if only firing on 3 cylinders and would slow to about 20 mph. It would throw every code on the laundry list. Usually took a few minutes to clear up and then run fine. Replacing the gasket cured that issue as well. If the whistle just started on yours it may progress to this point or it may not.

BlvdKreeper

Mines has been whistling for months now. It only whistles when I drive and when it's cold. If I stop to look for the whistle I stop hearing it. I'll check the bolt tomorrow. Thanks for the tip!

Warren Dwight Page

Ok, I put some champion plugs in, I cleard the code.
Seemed to run fine for a few days.
Now the engine light is back on.