Jeep Misfire problem

[SMLEshooter]

Thanks for all the advice guys, I'm working through them.

Here's where I'm at now:

Replaced both upstream O2 sensors. Didn't fix the problem, so I replaced the coil pack. That didn't fix the problem either.

So to recap, I've also checked compression, it's good on all cylinders, I've replaced the crank position sensor, replaced the plugs with Champion plugs, replaced the plug wires, replaced the fuel pump.

I'm going to replace the TPS next and then the cylinder one fuel injector.

 

[harrycalahan]

Cap and rotor?

 

[potenza]

Cap and rotor?

Coil pak!! No cap


You probably have a bad dead cylinder

 

[harrycalahan]

Coil pak!! No cap


You probably have a bad dead cylinder

Simmer down. Just covering the basics and I missed the crank position sensor part. Ive only serviced one jeep in my life anyways so im coming at this from a general perspective. He said the compression checked out too.

 

[potenza]

Simmer down. Just covering the basics and I missed the crank position sensor part. Ive only serviced one jeep in my life anyways so im coming at this from a general perspective. He said the compression checked out too.

Yeah I know, but I do it for a living. 200 k. Jeep motor , tired, bad cylinder. I hope I'm wrong and his fuel inj fixes it, we have a term for folks like him, bring it to us after you've run out of parts and money and let a pro diagnose it

 

[harrycalahan]

Used to make a living at it too, if you could call it that. Are jeep motors not noted for going much past 200k?

 

[potenza]

Used to make a living at it too, if you could call it that. Are jeep motors not noted for going much past 200k?

Most of it relies on the maint by the owner! They ner jeep motors have a major failure on valve trains at about 40 k

 

[harrycalahan]

Most of it relies on the maint by the owner! They ner jeep motors have a major failure on valve trains at about 40 k

If thats the case then he broke some kind of record for jeeps at 197k right? I wonder if his knock sensor is just picking up a valve rattle on decel from worn guides.

 

[galvatron]

If thats the case then he broke some kind of record for jeeps at 197k right? I wonder if his knock sensor is just picking up a valve rattle on decel from worn guides.

Most 4.2 and 4.0 Jeep engines will do 200-250k easy with minimal maintenance and mild abuse. It's a pretty solid little engine.
Knock sensors pick up vibrations from detonation while accelerating and the computer uses the signal to retard timing a few degrees. Backing the timing off while decelerating won't cause detonation or the misfire he's experiencing.
Easy way to test one, grab a timing light run it up to 2k and tap the area around the sensor and watch you timing drop off about 5 degrees. Don't hit the sensor....

 

[potenza]

I meant 2011/2012 and up 3.6 jeep motor failures
Biggest problem with 4.0 head gaskets