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272,000 mile 94 cherokee for a $100.

S

sik4wheeler

NAXJA Forum User
Location
Campbell, C.A
Hey guys I just bought my second cherokee. It is a 1994 4dr. and has 4wd 4.0 manual tranny and a np231. I scored this thing for a hundred dollars and almost made it home. It has a rebuilt dealer motor that has about two years on it and unknown mileage. It runs great when you start it up and then about 5-10 minutes later it sputters and dies. When it dies it will not restart for quite some time. I am getting spark, but is it possible that it could be the fuel pump? I havent had time to check it out much, but it will hopefully be an around town driver. Also after I get it going what are some good mods to get better mileage? My other cherokee is my wheeler/beater so this is going to be the new daily driver. Any suggestions or thoughts guys. Thanks for the help ahead of time.
-Nick
 
just check the fuel pump/pressure and filter. also give it a good $50 tune up with plugs, cap, rotor, wires, oil change, filter, and replace the injector o-rings of anything else
 
Change the CPS, had an old YJ do that to me, would run just long enough to get the engine good and hot, then sputter out and die. Had to sit on the side of the hwy for 30 minutes with the hood up, then it would crank right up...
 
yellowta said:
Change the CPS, had an old YJ do that to me, would run just long enough to get the engine good and hot, then sputter out and die. Had to sit on the side of the hwy for 30 minutes with the hood up, then it would crank right up...
Click to expand...

If he has a spark at the time it won't start, though, that pretty much rules out the CPS. ON a 94, a dead CPS should set a code.

I'd check fuel first.
 
Thanks guys. 1st I am going to replace the fuel filter and see how clogged it is. The plugs look good. It definetly needs an oil change as well as cap & rotor. Also, one time when it died the check engine light came on until started it an hour later.
 
selarep said:
just check the fuel pump/pressure and filter. also give it a good $50 tune up with plugs, cap, rotor, wires, oil change, filter, and replace the injector o-rings of anything else
Click to expand...

Change the air filter too, see if it is oil soaked, if yes replace the CCV lines. Also check the coolant temperature and Air intake temperature sensors to see if they are giving bad data when it warms up (ohm meter is all you need to test them). O2 sensor is also possibly kicking in after warm up (moving from open loop to closed loop) but giving bad data to the PCM and killing the engine with an incorect A/F raito (flooding it).
 
Ok I have changed the oil+filter, the air filter(it had oil on it) cap and rotor(had a decent amount of carbon in and on them), and I also changed the fuel filter (was not clogged). I havent hooked up a fuel pressure test, which I will do, but it seems to have decent pressure. I pushed in the release valve and it came shootin out(I did that 4 times). Could the injectors be bad and be the cause, because I was moving #2's injector and wires around and it seemed to help kill the motor/kill it. It also didn't die everytime or bog down everytime I moved it. I am going to check all the plugs and have a mechanic friend come plug his scanner to it which will check the sensors as well, but I will then afterwards go through the sensors and double check them if it doesn't turn up.
 
Ecomike said:
Change the air filter too, see if it is oil soaked, if yes replace the CCV lines. Also check the coolant temperature and Air intake temperature sensors to see if they are giving bad data when it warms up (ohm meter is all you need to test them). O2 sensor is also possibly kicking in after warm up (moving from open loop to closed loop) but giving bad data to the PCM and killing the engine with an incorect A/F raito (flooding it).
Click to expand...
That was my thought as well. Try unplugging the O2 sensor and see if the problem goes away.
 
Yah it's really interesting how a marginal poorly working, but working O2 sensor can cause a wide variety of REAL havock with the engine depending on the bad data it gives out, and yet a dead O2 sensor lets it run fine other than terrible gas mileage.

lawsoncl said:
That was my thought as well. Try unplugging the O2 sensor and see if the problem goes away.
Click to expand...
 
Took it for another drive around the block and the neighbors were looking at me as if I was learning to drive stick because when i tried to accelerate it would cut out so I push the clutch rev it up a bit let it back out and still hopping around. So, we plugged a snap-on scanner to it last night and a few things came up. The fuel injectors are missfiring and the TPS has higher voltage than it should. Also the fuel pump is working fine. I am definetly getting spark and fuel to the rail when it wont start but, I don't think the fuel is getting the the cylinders. We put gas in the manifold and it started then died. Since it wouldnt stay running or start we did a cranking RPM test to the CPS and when cold it was suppose to be hold 200RPMs but, when we did it while it was warm it was at 160RPMs. We are going to do more tests today after work.
 
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With it running fine on first fire up, then bad when warm, my bet is that when the computer tries to go into closed loop mode, a sensor is screwing things up. O2 most likely
 
Will it keep doing the same thing if I disconnect the O2 sensor and it is the problem or will it bypass it and act fine but, not so good mileage. If it is the 02 I will replace it right away.
 
sik4wheeler said:
Will it keep doing the same thing if I disconnect the O2 sensor and it is the problem or will it bypass it and act fine but, not so good mileage. If it is the 02 I will replace it right away.
Click to expand...

If it's a bad O2 sensor, unplugging it will throw a code and the computer will assume some default settings. It should run, but you'll get crappy mileage. You also mentioned a high TPS voltage. Might be worth swapping that between your other Cherokee to make sure that isn't part of the problem. Look at the grounds too - esp engine to firewall and battery. Have a look at the CPS sensor connector and wiring - make sure it's not melted against the header or something.
 
My other Cherokee is an 89 so I don't know if the TPS is interchaneable and also I didn't have time yesterday to look at things I had to change the alternator on my work truck and the water pump out on my gf's zj. Thank you guys for the help and hopefully I will have more about my xj tomorrow.
 
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