2004 Wrangler 4.0L Problems

[tobyw]

Chasing a problem on my 2004 LJ that's got the 4.0L/42RLE automatic...

About a year ago, after a long loose/rocky climb in the Naches area on a particularly warm summer day, the engine quit while idling at the top of the hill waiting for my wheeling buddy, and it would not restart for about 15 minutes. Ever since that day, the Jeep has exhibited a slight stumble/shudder at idle, is down on power and fuel economy, and has a notably different exhaust note, almost sounding labored if that makes any sense. One other thing I've noticed is that there is no longer any change in RPM when I shift between Park and Drive/Reverse. Usually idle RPM is slightly higher than when in gear and there is a small lurch, but there is zero change.

There is no CEL, spark plugs look fine, and I replaced the TPS just because I had one on the shelf and it made no difference.

I'd greatly appreciate any thoughts or input on what to check or look for?

 

[1982cj7]

Try cleaning the carbon, I use the Chrysler combustion cleaner per the instructions.

 

[WA-Wheeler]

IAC? Give it a clean. Oh and pictures....been longing for a LG past couple of years.

 

[TreeClimber]

Clogged cat? Would explain the down on power, and poor economy issues, and wouldn't set a Check Engine Light. Could also explain when it happened, as, under hard load is when they tend to break apart and jam up.

 

[KarlVP]

You could try to disconnect the muffler if it is clamped on and see if the cat is plugged.

 

[boardbysled]

Aren't those years Wranglers famous for vapor locking the fuel rail? Maybe vapor locked and damaged one of the injectors? Might be something to research a little further.

 

[tobyw]

Thanks for the input everyone!!

I have thought about a possible issue with the cat, will definitely see if I can tear into the exhaust system and give that a visual inspection. The change in exhaust note and general sluggish performance do seem to add up to something along those lines... :awesomework:

I've never heard of vapor lock issues on the Wranglers, but I'll definitely research that! Thanks for the tip!!

 

[1982cj7]

Remove the exhaust at the manifold and check the upstream cats they are the ones that always go out.

 

[the4x4pig]

Just gut the upstream cats. They are more problems than they are worth. If the computer complains just use the $5 extenders on the downstream o2 sensors. Of course if you have emissions checks that probably won't work.

 

[tobyw]

Tell me more about these $5 extenders?? I've got a buddy with a similar 2004 LJ that has hollowed out the pre-cats, and gets a CEL every few hundred miles that he just clears with a cheap code reader. Do these extenders fool the computer somehow to make it think things are back to normal and eliminate the CEL?

 

[Todd1803]

Tell me more about these $5 extenders?? I've got a buddy with a similar 2004 LJ that has hollowed out the pre-cats, and gets a CEL every few hundred miles that he just clears with a cheap code reader. Do these extenders fool the computer somehow to make it think things are back to normal and eliminate the CEL?

They sometimes fool the computer into thinking the catalyst is working and stop triggering the MIL. They basically move the downstream O2 sensor back out of the exhaust steam some, so it sees a difference between the readings from the upstream sensor.

Do a Google search for "spark plug non-fouler". You can order them, or my local O'Reilly's has them on the wall near the "HELP" parts.

Sent from my Nexus 10 using Tapatalk

 

[the4x4pig]

What ^^^^he said. When I bought my LJ the rear cat was gone. The upper two were clogged. I gutted them and used the extenders on the two downstream o2 sensors. No codes. Only issue was I had to get rid of my new flow master as it got really loud and developed a drone once the cats were gutted. I just put on a stock type muffler and it sounds like the flow master used to.

 

[tobyw]

Huh... so it literally just pulls the O2 sensor up and out of the exhaust pipe a little bit, cool!! I will have Jim try it out, thanks for the info guys!!

Back on my issue, I still haven't had time to get the LJ back on the rack to pull the exhaust system, but I'm hoping to get to it in the next few weeks. Luckily it's not my driver so none of this is mission critical...