I posted earlier but after going back I couldn't find my post...... here's the deal, I have a 00 Cherokee 4.0. I took it down the road and after a few miles it started cutting out, bucking and backfiring through the intake. Y'all originally said it was probably a voltage issue, and after inspecting the battery connections I thought so too. I replaced the connectors and drove it for around 20 minutes ( way longer than before). After 20 minutes it started the symptoms all over again. Once you hit around 40mph it really begins to cut out. I've tested the fuel pressure and it's consistently around 49psi. I tested the tps ( with key on, motor off) by measuring volts on the sending and reference wire. I have a solid 5 volts going to the sensor,and with butterfly closed around.88 volts. What I'm unsure about is when I test with butterfly wide open I'm getting 3.88 volts. The thing can sit and idle all day long without failure, but shortly after hitting the road it starts acting up. I really need some help guys and gals.

 

I forgot to mention that the check engine light is not on and no codes were found after using a scan tool.

 

Check your spark plugs? Air filter? Intake tube for cracks? Throttle body gasket? Vacuum lines?

 

What kind of maintenance has been done to this, if any?
How many miles, is it a beater, how did all this start?
Have you done a compression test and what are the results?
Does the CEL illuminate at all?

 

Was gonna suggest the same thing. I would start here. Start simple.

 

it has 120xxx miles. Not a beater. as for prior maintenance I have no idea. I bought it about a month ago and just now got around to driving it. Air filter is new, there were a few broken vac lines which are now fixed. I haven't checked the plugs, but I will. CEL illuminates at initial startup then goes away upon starting. Sprayed carb cleaner around everything and found no vac leaks. The PO put a new gasket on the intake/ exhaust side. He was definitely not afraid to off-road it because there was a ton of dried mud under it. Mechanically it seemed pretty solid and actually drove out fine initially. The only maintenance I did was solder some wires together that had apparently been chewed on by a rat. Doing this got my taillights and brake lights working. I also put new wheels/ tires and a 3" lift ( front springs, rear add a leaf), but that's irrelevant......

 

I would check that intake/exhaust gasket. Could be the culprit

 

Finally got it to stall out while I had fuel pressure gauge attached. Once it stayed sputtering and popping I noticed the fuel pressure was around 20psi.