[BirdWatcher]

I really need some help, when my JK runs bad I'm not happy. Just started to backfire out of exhaust it sounds like. Each time I lug the motor a little when first accelerating from a stand still. Sounds like a small pop in the exhaust system right near the engine and not down very far from the exhaust manifold. I could be mistaken and this pop could be in the intake even. Other wise runs fine and normal. This doesn't always happen. This is stock 3.6 2008 JK Unlimited. 25,000 miles well maintained.

Any one else have anything that might sound like this or similar experience? I really don't like to go to the dealer if I can help it. Thanks for your experiences, Dennis

 

[havasu]

Go to a business which will provide a free OBD-2 read out and let the jeep computer tell you what the problem is. I know Mayco and Pep Boys usually will scan it for free.

 

[BirdWatcher]

I haven't visited lake Havasu for a while. It's cold,where I am in the mountains of Colorado. Thanks for the tip. I recently made two trips of about two hundred miles each, and it never acted up one time during or since! Lately all of my Jeeps trips had been real short. Possible some build up in the throttle body? Problems usually never just disappear. Have a great day and Happy New Year!

 

[havasu]

I know the ethanol based fuel many of us are using really sucks for engines, and the fuel breaks down real fast. I'm wondering if you just had some rotten fuel like I get often?

 

[BirdWatcher]

Even if bad fuel didn't happen to be the problem I have to admit I buy from a off-brand discount gas station because in our small town it is just convenient. Fuel quality likely has some effect in this situation and I had just mentioned that to my wife. We will use name brand fuel in the future. I think there is an air gap in the throttle plate that only passes air that can be looked at and possibly cleaned. This doesn't come into the fuel quality question because only air passes this point. BUT, and I need to find out about this, I think that contaminated air does pass because of the exhaust gas recirculation system. I believe that cleaning the throttle body at one time was a maintenance item but haven't heard much about that operation lately. Anyone else have something to add to this direction?

 

[eumel789]

How many miles do you have on it? Remove the air cleaner hose and look down the throttle body with a flashlight. That may give you a clue how to proceed. Also, put some name brand fuel additive in the tank every other tank full. That also fights water in the tank and keeps everything clean.

 

[RikRotorhead]

Pour some Motor Max if you can find it into the tank and run the tank out. It sounds like bad gas and you are getting pre-ignition.
Motor Max is great stuff. It's a little more expensive than the other brands but I've used it and it works fantastic.

 

[BirdWatcher]

Thanks everyone! I think that a trip to the dealer service department has been avoided. The problem was surrounded by lots of information until it got fixed. In hind sight the trouble was so simple that I have to admit I ignored the obvious. Is, "Motor Max" anything like "Marvel Mystery Oil"? This has been around for a long time also and I do use it specially in small motors and generators or snow Blowers which sometimes don't get run too often. It works great in keeping old carburetors, floats and main inlet needles clean and from sticking. Thanks again- Dennis

 

[RikRotorhead]

It's similar but faster action and works on more levels.
So what was the problem?

 

[BirdWatcher]

Well... What was the problem? It kind of went away over a period of a few hundred miles of harder driving, on the interstate with good gasoline and chemical cleaners. I'm guessing that the problem is gone. It could come ,back and it is entirely possible that it is something more serious. My Jeep had been driven short trips and very low speeds around town. More time will tell and I will keep you posted. I know that real problems don't just disappear magically. Dennis

 

[07wranger]

i just had similar symtoms and they dropped my tank to find half of it was water!