So im currently driving a 99 cherokee XJ 4.0. Ive noticed that recently when I start it I get a shift in rpm and a quick one sput sputter now and then.

I noticed tonite while on the freeway that it would sput/very light jerk, while driving around 60mph.

Anyone else encounter the same problems?

Im gonna start troubleshooting with the fuel filter, then move to spark. We'll see!

Any help would be greatly apprecited!

When was the last time you replaced the fuel filter?? That is one often overlooked preventative maintenance that should be routine...

Also, check your fuel pressure. I have had similar problems with a bad fuel pump. Mine was more evident with engine warm and under load.

Also, are there any trouble codes?? Check engine light??

Typically the spark plugs show up at hiway speeds. How many miles since the gap was checked? Fuel filters usually show up at the highest load on them.. Steady 60mph would be about the greatest load on the plugs themselves.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Drove it again today, same deal. Its like a real quick hesitation every 5-10 seconds at freeway speeds. No, I has not thrown any codes, which is odd.

I had the pump replaced a couple years ago, im assuming they did the filter too because isnt that part of the pump? And isnt the fuel filter in the actual pump itself?

I also replaced plugs/wires/cap/rotor about 18 months ago. Since then I have not toutched them.

Spark seems logical! So does fuel! I guess ill start with the plugs and go from there. Wish me luck, im not working at a shop anymore and am really missing the access to supplies....

Plugs and wires are the thing to look at for a felt miss. 30K is the normal interval on plugs, 60K on wires, cap and rotor. Look for corrosion where the wires connect to the cap terminals, any found and it's time to replace them. Mopar wires are date coded.

On the 99 4.0l, it will take a few misfires in a row, within a certain amount of time for the code to set, but it you were able to watch the misfire monitors with a scan tool, you can see which cylinder is misfiring. It may have set a one trip fault, for which the light won't come on. Also, misfire faults are disabled with less than 15% fuel level in the tank.

Fuel system supply restriction issues (Filter plugged) will usually feel like a sag or lack of power until you cut the throttle, when they first start. The fuel filter is built into the top of the pump module, and it is not a normal scheduled maintanance item. It should be replaced when a pump is changed. The pump module also has a large, fine mesh pickup screen

A intermittant injector can cause a single cylinder miss. Injector Circuit issues will usually throw an immediate code though. A plugged injector usually stays plugged once it happens, causing a consistant miss.

Hope this helps!

Fixed!

Its not too often I have a quick fix on my vehicles, so far the Jeep has been a good buy!

I started with replacing all 6 plugs. While replacing I noticed that the Cyl 6 wire was fried where it clips into the plug. So, I plugged it back in and drove back to the parts store(check engine light came on).

At the parts store I checked the code and it came up as a "Cylander 6 misfire. I then proceeded to replace the #6 wire, cleared the code, and that was it!

Thanks all for the help!