rough runnin xj

I Have a 2000 jeep cherokee sport with a 4.0 that has began runnin rough at idle and pops thru intake at speads sometimes i have replaced the plugs air filter fuel filter but that hasnt helped anyone have any ideas

The fuel filter is part of the fuel pump "assembly" which is located on top of the gas tank; tank has to come down to replace.

Did you replace only the filter part of this assembly? Need some details.

Verifying fuel pressure WITH A FUEL PRESSURE GAUGE is never a bad idea. It hooks up to the schrader valve on the fuel rail. Looking for 49.2 psi for your 2000 plus or minus 5 psi.

Any check engine light? If so, you must pull codes for guidance.

replaced pump and filter checked the computer for codes showed no past or present codes scanner showed the o2 sensors were fine it just actin realy wierd

reaper1972 said:

I Have a 2000 jeep cherokee sport with a 4.0 that has began runnin rough at idle and pops thru intake at speads sometimes i have replaced the plugs air filter fuel filter but that hasnt helped anyone have any ideas

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Welcome aboard......

Check your compression. You could have a burnt (or hanging) valve.

Does it ALWAYS run rough at idle, or only when cold and after a hot restart?

runs rough either hot or cold but most of the time it runs fine its just a periodic problem thats drivin me crazy

B.RAIDER said:

Welcome aboard......

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:rof:

Ok, try this: get the engine good and hot, like a highway run. Park, shut off the engine. Pop the hood and leave it open for at least 30 minutes.

Start the engine, if the symptoms are less you may have heat soak. Same thing applies before parking overnight.

Heat soak is a known condition for the 99-01 XJs with the 4.0 engine. Essentially the fuel is boiling in the number 3 cylinder's injector.

TSB 1803103 - 4.0L ROUGH ENGINE IDLE AFTER RESTART FOLLOWING A HOT SOAK
Date: 09/05/03 (supercedes 1802702 dated 09/06/02)
Model Year(s): 1999-2004


The "fixes" are a change to NGK spark plugs, an insulating sleeve for injector number 3, and a heat shield at the manifold.


the FIX is lowering the under hood temperatures after shut down of the engine. An electric fan timer set for about 5 minutes of efan operation after the engine is shut down seems to do it: http://www.at-fairfax.com/P1786-ELK-960.htm

finnaly fixed the jeep turned out to be a coil pack problem one of the boots was torn and arcing off the head replaced coil pack and now runs better than a new one.thanks everyone for your ideas

Good job