Gudenrath

So I've been searching this forum and everywhere else for a couple months now and I have no idea what my problem could be. I have a 96 jeep Cherokee sport i6 130,000 miles. It starts right up just fine, no leaks, no overheating, idle is fine at first, oil pressure is fine, replaced the water pump, fuel filter, oil pressure sensor, and spark plugs. When I start it up it starts up just fine, but if I drive it for more than 10 miles or if I let it sit and idle for more than 15 minutes then it sounds like it's running out of gas and sputters and it keeps getting worse until it will finally die (all while idling). This will happen if I let it idle for 15 minutes or so, and if I drive more than ten miles, shut it off (run into the store or whatever) then when I turn it back on it sputters like it's about to die. But when I start driving it's totally fine and I can go down the highway and it doesn't make any weird noises or have a loss in power or anything. This problem only occurres after it's been running for a while and it's idling. If any more info is needed please let me know and I am dying to figure this problem out because it seems like no one else on this forum has experienced the same thing!

dzywicki

I had something somewhat similar on my '99. Idled fine when cold, but after it warmed up, idle was terrible and would occasionally die out when going to reverse. At speed, it seemed fine. I replaced several sensors and checked everything and could not find/fix the problem. I eventually went back to the spark plugs. I had used autolite for some reason. I switched back to the Champion coppers and all my idle problems went away. Wouldn't have believed it before this. Might be worth a try if you have eliminated everything else and you have some besides the OEM Champion coppers in there.

Gudenrath

Yea I used the champion spark plugs. Another thing it does when it's "dying" is it has hardly any power. I'll put it in gear and put the pedal to the floor and it hardly goes anywhere. I just pump it a few times and it comes back to life and runs normal. Almost seems like a fuel pump issue but I can hear it come on and it doesn't make any weird noises. This is my first jeep so I don't have a whole lot of experience but every other problem I've had I've been able to find a solution by looking on this forum but for this problem I'm completely stumped.

Gudenrath

I'm taking it into firestone today for a diagnostic and I'll post what they say is wrong with it so anyone on here can tell me if it's legit or not. I want to fix it myself but I don't want to waste money on parts I don't need.

cruiser54

Test the fuel pressure.

moparado

After you check the fuel pressure and 'if' its OK....
This sounds like the infamous 4.0 heat soak problem. There's a TSB for my 2k xj but not sure if it applies for a 96 XJ.
Maybe Cruiser54 knows.

Tank24

I had similar issue on my 96 XJ Country. If everything else checks out, it may or may not be a clogged exhaust. Mine would run fine on start up and eventually once warm, it would lose all power and would shut off; could put the pedal to the metal and would run rough and surge. Long story short, the converter disintegrated clogging the muffler.

Alex V.

FWIW the one vehicle I've seen with a severely clogged catalytic converter (throttle body injected Dodge 360) would idle great but refused to rev above 1,000 RPM, and the more gas was applied the more black smoke it belched, as much as a straight black cloud at its worst. Idled great but wouldn't pull itself over 5 MPH.

Possibly something with the fuel injection system that's not functioning right once it goes out of open loop?

cruiser54

Can be tested.

Cruiser’s Vacuum Test for Exhaust Restriction

Your vacuum gauge should come with an instruction booklet outlining this procedure.

Hook the vacuum gauge up to a source on the intake manifold.
Start the engine and note the vacuum reading.
It’s usually 17 to 21 inches of vacuum.

Throttle the engine up to 2,000 to 2,500 RPM for 20 seconds or so and the vacuum reading should stabilize to the same reading you got at idle.

Let the throttle snap shut. The vacuum reading should shoot up about 5 inches of vacuum higher for a second and then come quickly down to the original reading.

If the vacuum reading stays high and comes down slowly with jerky needle movements, you have an exhaust restriction.

Gudenrath

Firestone said it's as simple as replacing my O2 sensor after the cat. I thought that one didn't affect how much air is put into the fuel, it just made sure the cat was working. I can't get that sensor out for the life of me but would a bad O2 sensor cause my problem?

jordan96xj

Gudenrath,

If when it begins to sputter/die, you give it just a little gas pedal, does it smooth out and run properly? If so, you need to service the throttle body (remove and clean), and most likely replace the Idle Air Controller (IAC). Relatively simple and inexpensive job.

Gudenrath

I've already taken the throttle body out and cleaned it and cleaned the iac. Maybe the iac needs replaced but the rpms never change when idling when the problem occurs and they stay at 500. I have to really slam on the gas for it to regain full power

Gudenrath

One of the spark plug wires wasn't pushed down all the way so it was a little lose but I pushed it in as much as I could and it seemed to fix the problem

rgr4475

Thanks for coming back and letting us know.