I have a 93 yj with the 2.5l. I've been chasing this hesitation problem for the last 4 months. It runs fine, but when it gets between 2500 and 3000 rpms at a steady cruising speed, it hesitates like it has a misfire. When it happens, sometimes it backfires out the exhaust and sometimes it dies completely. If I push on the gas or let off it completely, it stops. Just does it between those rpms. It does it whether it's warm or cold. It doesn't matter what the weather is like, it still does it. It doesn't throw any codes either. It idles fine. Runs good until those rpms, but sometimes it feels a little underpowered, other times it runs like a raped ape.
So far I have replaced the cap, rotor, distributor, tps, crank sensor, plugs, wires, fpr, and fuel filter. I've checked all ground wires and vacuum lines. Everything was good there. I have a slight exhaust leak where the down pipe bolts to the manifold. Checked wires going to O2 sensor, they're in good shape. O2 sensor is less than 2 years old. Fuel pump is about 2 years old. Haven't been able to check fuel pressure yet because nobody rents them out around here. Please help! I'm starting to lose my mind.
No codes being thrown. The CEL hasn't lit up once while doing it, and I check every so often to make sure I didn't miss one. Nothing has been stored. All it shows is 12-battery has been unhooked, 33-typical ac code and mine doesn't have ac, and 55- end of codes. I wish the CEL would come on so I had a point of reference.
maybe you have low fuel pressure, and your pump cant keep up at high rpms. youre obviously losing something at that rpm range;least likely compression since you have no cat and this engines hardly ever jump time, so you could either be loosing spark, fuel pressure or injectors pulse, could you hook up an oscilloscope to the ckp?
I don't have access to one. A friend of mine is going to bring me a fuel pressure gauge from his work. Hopefully that will help figure out this problem. I drove it around a little today after I cleaned the IAC valve and throttle body, but it didn't help. It actually felt a little worse, and now it does it when I step on the gas. Almost feels like it's running out of gas, but there's at least 5-6 gallons in it.
Checked all of the wiring, cleaned up all of the grounds, new OEM crank sensor, and brand new coil. I'm getting good spark at all plugs and they are all a light tan color. I'm at my wits end. Took it out today, and it starts and idles great. Once you get on the skinny pedal a little, it falls on its face. Like it's almost out of gas. I think I'm just going to drop the tank and change the pump. It's the only thing I haven't done yet.
Was getting 20 psi when it should have been 31 psi, so I changed the pump. Ran great for about 10 miles. When I turned around to go home, it died out on me and wouldn't start back up. Had to have it towed back home. I let it prime a few times to build up pressure, but there's not much pressure in the rail after doing this. Before it died though, there was no more sputtering. I thought my problems were solved.