Jeep and Gas

Boomerang · **Joined:** Tue Jul 26, 2011 7:46 pm **Posts:** 184

How come they recommend using regular unleaded which makes my KJ idle rough when the premium fuel immidiately smoothes out rough idleing? Maybe the engines run better on the premium, but because they get such hellacious gas mileage jeep recommends using the cheapest stuff so they can parade the idea that these vehicles are chepaer to own?

Zack A · **Posted:** Mon Sep 19, 2011 5:01 pm

I run mid-grade, seems to work good. Smooth the idle out and slightly better MPG. But it is a jeep and I didn't buy it for the MPG.

Boomerang · **Joined:** Tue Jul 26, 2011 7:46 pm **Posts:** 184

But of course on the mileage, except that I would not buy one of they all got 10MPG.
Mileage wasn't my thought, it was the way it runs. Technically it should be a healthier engine the smoothers it's running. Health = longevity.

liquidxit2 · **Posted:** Mon Sep 19, 2011 6:41 pm

They recommend mid grade for towing, other then that i would look into the issue thats causing your 3.7 to run a bit rough on 87.

Boomerang · **Joined:** Tue Jul 26, 2011 7:46 pm **Posts:** 184

been working on it. changed the plugs, cleaned varieous components,... it is smoother than it was when i started... but when i say rough idle, we're talking smoooooooooobumpoooooothbump..... nothing dramatic, but not correct.

MonsieurGlen · **Posted:** Thu Sep 22, 2011 8:57 pm

Boomerang wrote:

been working on it. changed the plugs, cleaned varieous components,... it is smoother than it was when i started... but when i say rough idle, we're talking smoooooooooobumpoooooothbump..... nothing dramatic, but not correct.

Others on here have spoken about valve problems on the #3 cylinder. It has something to do with the way that it is supposed to auto adjust but doesn't.Have you had that checked out?

mikey1273 · **Posted:** Fri Sep 23, 2011 8:23 am

every gas powered vehicle I have owned has always idled a tiny bit rough on 87 gas. a tune up and a seafoam treatment might be what you need. My Subaru used to smooth out after that, and like mid grade much more also but boxer engines have a different sound and feel when running than anything else. Now I have the CRD and never drove a gas V6 Jeep. All the ones I have been around sound smooth and quiet to me.

Boomerang · **Joined:** Tue Jul 26, 2011 7:46 pm **Posts:** 184

MonsieurGlen wrote:

Boomerang wrote:

been working on it. changed the plugs, cleaned varieous components,... it is smoother than it was when i started... but when i say rough idle, we're talking smoooooooooobumpoooooothbump..... nothing dramatic, but not correct.

Others on here have spoken about valve problems on the #3 cylinder. It has something to do with the way that it is supposed to auto adjust but doesn't.Have you had that checked out?

Have not looked into this and will. Something only a mechanic can do? I'm thinking about having a compression test ran as well..

mikey1237 - i did the full seafoam treatment plus new plugs, synthetic oil and air/oil filters a couple weeks ago. Helped a lot, especially in restoring quite a bit of power. I'm sold on seafoam, but cautious of it as well.

mikey1273 · **Posted:** Sat Sep 24, 2011 12:39 am

cool sounds like you are doing all you can then. Seafoam is good stuff if used correctly. i just used it to clean my fuel injectors by filling my diesel filter with it during a change. ran the engine on it a minute stopped it waited 10 minutes then went for a drive. I can't use it the same as you can with gas

dieselenthusiast · **Posted:** Sun Sep 25, 2011 11:52 am

Have you changed your PCV valve?

Boomerang · **Joined:** Tue Jul 26, 2011 7:46 pm **Posts:** 184

dieselenthusiast wrote:

Have you changed your PCV valve?

yes, with the plugs

Boomerang · **Joined:** Tue Jul 26, 2011 7:46 pm **Posts:** 184

filled up yesterday, averaged 14.5 MPG freeway mostly
Best i've had was 17

dieselenthusiast · **Posted:** Mon Sep 26, 2011 11:03 pm

A sticky EGR valve will also cause it to run rough and result in poor fuel economy.

Jeep and Gas

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