rough idle 4l

M612 · #1 (**permalink**) 03-13-2005, 10:25 AM

I just bought my first lasyt April Jeep 2004 Unlimited/4.o/Auto Trans/Soft Top. It Idles rough and gets only about 9mpg. Took it to the dealer and they said that is normal for a 4.0. Is it? Or is the dealer avoiding the problem.

SenorCole86 · #2 (**permalink**) 03-13-2005, 10:32 AM

Holy mackerel. I'm no expert on the 4.0, but I seriously doubt 9 mpg is normal. I SERIOUSLY doubt it. I hope somebody else a little bit more informed will help ya out. Might wanna try the tech forums though.

southtj · #3 (**permalink**) 03-14-2005, 09:09 AM

I have an 04 4.0 and that is definately low. I average about 14 city and about 18 hwy and while not great that's better than 9! I'd go back or if you can try another dealer.

anthonyp · #4 (**permalink**) 03-15-2005, 11:13 AM

I have an 04 Wrangler X with a 4.0L I6. We've never got less than 14mpg, even in stop and go traffic commutes. We're usually around 17mpg though. Mine's a 5 speed with a 3.07 axle ratio and 30" tires. If you've had this problem from day one, then I'd definitely follow up with another dealer or even go straight to Chrysler Customer Service with a complaint....especially if you are under warranty. If the problem is somewhat recent, then I'd recommend buying a high quality fuel injector cleaner ($10) or having the fuel system professionally cleaned ($35) just to make sure you have not picked up a bad batch of gas or something. Either way, find a reputable dealer and get it handled under the warranty if you're still covered. 9mpg is way out of line...in my opinion. THAT SAID....one small extra piece of info....for some reason my 4.0L runs rough on 87 octane, even though that's the recommended. We always put in the 89 octane now. I know gas is expensive, but if you're going with the low grade right now...run it down to the "ding" (that "ding" low fuel warning sound scares the CR@P out of my wife ever time it goes off) and then fill up with 89 or higher...just as a test.

laneiac · #5 (**permalink**) 03-16-2005, 05:33 PM

My 4.0 idled rough and I ran 92 octane through it an voila! I am sure I have some ignition problems but it may work for you. 9 MPG is way too low. Both of my jeeps get around 14-15.

M612 · #6 (**permalink**) 03-20-2005, 10:01 AM

well I ran injector cleaner thru with a tank of 89, no change.
I also noticed the idle fluctuates between around 300 and 8oo.
I checked for codes with the trip reset and key on deal, nothing.
I will bring to dealer again tomorrow see what happens.
I think they stall for a year to avoid the lemon law crap, PA is 1 year I think.
Thanks for Ideas

MerkL · #7 (**permalink**) 03-20-2005, 07:01 PM

You will probably not get the same gas mileage as most of these guys b/c you have an Unlimited. It's bigger, longer, than a regular Wrangler, so expect somewhere between 12-14 miles per gallon.

M612 · #8 (**permalink**) 03-23-2005, 06:38 PM

took it to the dealer.
they said the distributer was out of synch and replaced 1 spark plug.
seems to run a whole lot better. Idle is staying around 750 and not so rough. I will run a couple of tanks of 89 thru see if it is really fixed.

ahunt01 · #9 (**permalink**) 05-09-2005, 01:01 PM

Did it fix your problem? Just curious. I have a 2005 Wrangler Unlimited and it idles kinda rough also. I too run 87 octane, and also notice slight pinging/chirping from the engine bay when driving under strain. I'm hoping it's just crappy gas/too low octane.

Bounty__Hunter · #10 (**permalink**) 05-09-2005, 01:16 PM

If one jeep off the assembly line had the distributor gear out of synch, it could happen to others. Has the dealership looked at it? Have to mentioned this possible problem?

ahunt01 · #11 (**permalink**) 05-16-2005, 08:17 PM

Guess it did, he isn't replying...