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96 Cherokee powerless, bogs when trying to accelerate

J

Jesusfreak0190

NAXJA Forum User
Location
Crane, Missouri
I just went and bought a 96 xj with 6.5 inches of lidt and 35" tires, the guy I bought it from said he swapped out the engine with a 93 ZJ its still a 4.0 though. the only problem I am having is when I lay into the petal the jeep bogs down and backfires sometimes but its just all around powerless, when I put my foot into the gas petal, its firing on all cylinders. I replaced the map sensor cause it was throwing a code, that helped a little but not much. It was also throwing a code for the o2 sensor before the cat. Could that cause it to run so crappy? I am beginning to think its the fuel pump. any help is appreciated!
 
Take a look into why you are getting the o2 sensor code. A bad o2 would cause the driveability issue you have described.

Check for loose/frayed wires. Check the fuse in the PDC. I've had the best luck with OEM o2 sensor's, the cheap ones never seem to work right.

If you still think it's the fuel pump, put a pressure gauge on the fuel rail.
 
ques:
How is the gas mileage?
umm restated "Are you getting 10 mpg? or normal 16mpg?"

I like the cheap approach. may not be fastest way


guessing you know this. too much fuel. maybe fuel regulator?
check fuel filter.
check fuel injectors. clogged?
check spark (dirty plugs will confirm too much fuel, clean/replace retest)
check air intake/ throttle body. look for carbon deposits. clean...

I probably try to reflash the pcm.
no expert: i might try to unplug the sensors and see how she runs. gotta buddy you can swap sensors with? or just head to the adult playground.. aka the junkyard !
 
Check all your major connections, grounds, pos +, And I agree with RadioShack just check your FP at the rail. to high or low and youll be able to narrow it down. I had a 5.0 AWD explorer with the same symptoms, random loss of power, rough idle, bad mileage 5-6 mpg etc. etc. Fuel pump died, replaced it with an oem and fired right up.
 
Also, check to see if your fuel pump is leaking gas from one of the metal tubes. Mine recently did this.

Turned out to be a brazing that had rusted out causing it to suck up air and throw it through the injectors. My jeep did not like this. Took out the pump and got it brazed for $20, threw it back in and it ran better than ever.
 
Check your O2 sensor as already mentioned, especially make sure the PO routed the cable to it properly. It's supposed to go around the intake manifold right behind the power steering pump and be secured to the side of the motor with a clip just above the oil pan, if the previous owner routed it around the front of the intake manifold between the PS pump and the motor (i.e. right near the serp belt) it can easily land on the #1 exhaust manifold tube and melt through, which will short it out and cause issues or blow your ECU.

Other stuff - check fuel pressure for sure as already said, and check if your VSS (vehicle speed sensor) is connected properly. If your speedo/odo work, it is working.
 
i pulled out some plugs and they looked clean enough to spark pretty good. the guy I bought the jeep from said it didnt start messing up till he drove it though some water. last night when I got off work it was a little cold and damp, the jeep ran like it was off the line at the factory, but only for about six miles once it warmed up it started running like crap again
 
another thing is when i took it to autozone they ran the code reader on it and the only codes it pulled up was something about the engine running to lean and another one said the engine was running rich, kind of strange to get both codes
 
Still sounds like that up-stream o2 is bad, missing, or not working as it should.

Someone correct me if I wrong but I believe the Coolant Temp Sensor can mess up the A/F ratio as well.
 
Jesusfreak0190 said:
the guy I bought the jeep from said it didnt start messing up till he drove it though some water.
Click to expand...

If he took it through water, it's possible that the TPS got soaked and is causing the symptoms you're describing. I've killed a couple doing exactly that and both times it felt almost like transmission failure, but with bucking/surging/hesitation under different loads from the accelerator. Not saying that is the issue, but is worth keeping in mind.

last night when I got off work it was a little cold and damp, the jeep ran like it was off the line at the factory, but only for about six miles once it warmed up it started running like crap again
Click to expand...

One other possibility is a dead catalytic converter; I've also seen the same thing happen when they're shot.
 
I can't believe no one's said it yet. Get the exact OBD codes. There's no sense guessing what might be wrong, when the PCM is telling you where to look first.
 
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