What's rough about it? Vibrations or does it seem to be missing?

If it's vibs, check the belt for tightness.

If the belt's tight and/or its missing instead, may be the o2 sensor. No codes I assume?

 

A little bit of both but more of a missing and yeah, no codes at all and the rpm's dont change.

 

checking the belt is free and quick and simple.

 

Ok, I'll give it a look tomorrow and forgot to mention that when i turn the AC on, the roughness is cut in half, Idk how that could make any difference, but it does...

 

Mine has always had a rough idle. I seafomed it twice, replaced spark plugs, cleaned throttle body and IAC, checked TPS, new exhaust (nothing to do with idle), and none of that made any difference at all. I replaced my rear o2 due to a CEL and it got a little better but still does it. But it's not all the time now.

I cannot figure it out and no longer care. It's just a part of my jeep apparently.

 

Well I checked the belt and it is in good shape and is tight. I know that some engines just run a little rough, but I would think that there would have to be something wrong that I could fix to make it not so rough. I wouldn't think its good for the engine.

 

While I was home from the Sandbox and drove our Jeep first thing I noticed was the rough, non-consistent Idle. Just on whim I bought a can of Sea foam, put most of it in a tank with an 1/8 of gas left. I then pulled the intake tube off the TB and dumped Sea foam in the IAC slot a bit at a time till the engine started to choke and smoke a bit. After about five minutes of the smoke and choke dying out I took it for a run and it was instantly better. Even Nikki who didn't notice the idle before says it runs at lower RPM and she sees the Mileage is better. I am going to make this part of my maintenance ritual on the Jeep.

 

Yeah, I've seafoamed my truck before and it worked pretty well, it's just that I replaced my plugs about a month ago and I heard that they can mess up the plugs.

 

I dunno about others but in this case I am using the same plugs and never even pulled them. Runs great

 

Throttle Position Sensor?

 

Maybe??? Do you have experience with that?

 

I had a mechanic tell me it is caused by the 2 rear injectors getting hot because there is no insulation between them and the block. I beleive it affects the 04 thru 06 Wranglers.The warmer the engine the worse the problem. I think there is an after market kit to remedy the problem. Good luck

 

Mine runs rough as well, Replaced the plugs with double-platinum and new wires last weekend, runs a bit better but still rough. Next is getting the fuel system/injectors cleaned and tuned up. I don't think it's ever been cleaned, at least according to the notes the PO kept in the manual.

 

My 04 4L auto was running rough. So bad I was freaking out every time I was pulled up at a red light. Turns out the air filter was 4 years old (I had just bought it) and had a strange felt cover on top of the paper filter. Looked very restrictive. So I swapped it out for a K&N filter and legitimately instantly my jeep was running totally smooth.

I had also put a bottle of some injector cleaner in the night before but don't think I'd driven enough for that to be what fixed it.

 

Get a paper filter that actually removes the grit as a K&N grit passer is a piss poor filter that passes enough grit to wear engine out much sooner then if you used paper

Just run it a few weeks then see how much grit is on air tube inside wall past filter

Paper filters were one of the biggest reasons engines started lasting longer


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Exactly what brand & model # plugs were in it before and exactly what brand & model spark plugs did you recently install in it? Newer distributorless 4.0L engines like you & I have are very fussy about what spark plug technologies they'll run well on. There are some spark plug guides that will say certain spark plugs are compatible but they're not.

For example, spark plugs like the Autolite AP-985 and Champion 3034 are platinum but their platinum coating is on just one side of the gap. That causes problems for "waste spark" design ignition systems like our Jeeps have... misfires, bad idles, etc.

Other designs like the Autolite APP-985 and Champion 7412 have their platinum coating on both sides of the gap which works well for the newer 4.0L engines with the waste-spark ignition system. Those will perform well for 100k miles. Autolite's iridium-tipped XP-985 is another great choice and is what I run, it will perform well for over 200k miles.

 

What about the Champion 7034 Double Platinum Power Spark Plug? Anyone have experience with those and rough idle?
p, li { white-space: pre-wrap; }

 

I don't think Champion still makes the 7034 which I used to recommend a lot, I'm pretty sure it was replaced by the 7412. No doubt the 7034 is still being sold by some but the 7412 is what is now recommended for the newer TJ 4.0 engines with the coil rail (waste spark) ignition system.

 

Those 7034's will be fine, no worries. ��

 

Recently had a rough idle on my '06 out of the blue. No other issues. Found an old thread about exhaust valve deposits on prior yr 4.0s. It stated the valves rotate above 3200 RPM. Ran some fuel system cleaner through it and did some higher RPM shifting and no more rough idle. I had been idling in line to get on base for approx 15 - 20 mins ea morning with no hwy driving when this happened.

http://www.wjjeeps.com/tsb/tsb_wj_0900303.pdf

 

I have an O2. Since it has 19 year old sensors on it, I replaced the air intake pressure sensor, the air intake temperature sensor, the throttle position sensor, cleaned the intake air controller, swamped the injectors with 4 hole injectors. Have it smoke tested for vacuum leaks. Mine runs like a champion now.

 

I'm on this path now and making sure I have just enough essential parts along the way. I will do my best to check back in at this thread when I get it sorted.

 

Ok. I have a 2004 Rubicon. 4.0, 5 spd, 148000 mi., bone stock. I too have a rough idle. Replaced TPS, IAC, Spark plugs changed to Autolite APP985, checked for vacuum leaks, switched to premium fuel, cleaned throttle body, replaced motor mounts. Still have rough idle. What next?

 

Do you have the same rough idle when the engine is cold?

Also, don't run premium fuel. It won't help in the least, not to mention it can leave deposits behind in an engine not designed for higher than an 87 octane.

 

I think the one thing I'm not sure of is if the 4.0 is capable of non-ethanol which tends to trend in the 89 octane range. I'd imagine the engine is specifically engineered for 87 and garbage but I often doubt my own self. Is anyone familiar? (yep, wrong thread)

 

Welcome to the Forum billlscott,

Good Luck, L.M.

 

Throttle position: Standard TH189
Air intake temp. Standard AX489
MAP sensor. Spectra MP106
All from Rock Auto.
After a 300 mile trip yesterday, my mileage is up to 17.7 from 15.
Droning is gone. Acceleration is good. Happy Happy.

 

I did the same so far with Standard for the TPS and Air Intake Temp. So far, the idle has smoothed out a bit but I still have a tremor/falter/shimmy or shake in there somewhere. I'm planning on coil pack down the road, MAP, O2 sensors (Mopar) and any thing else that skins my knuckles or just looks funny.