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Ughhhhh!!! Now i'm pulling my hair out.....

moparjim1987

NAXJA Forum User
Location
pennsylvania
Ok...now i've posted a couple of times before about my cherokee's crappy running situation. I'll give you a rundown on what i have done so far: when i got it, i cleaned the throttle plate and ran seafoam through the intake system. then i replaced the tps, cts, cps, and the evap purge solenoid. then today, i checked the fuel pressure and it held steady as a rock, @ 45-50 lbs. So basically what my problem is, is i will take the truck for a drive, then shut it off, wait for about 10-20 mins, then when i go to start it, after about 1 minute of running it starts stumbling and idiling really low, like 350-400 rpms. then i can goose the throttle and it clears up and runs fine. then when you go to drive, it runs out first gear fine then when it hits second, it acts like you cut the fuel pressure in half and it stumbles again but if you let off the gas, it runs fine and then it never does it until you shut the truck off. i appriciate any and all help on this matter. :bawl:
 
Shorty said:
any more info? like what year, engine, trans, mods.. etc

X2:wave1:
 
And how many miles on your engine??

Looks like you've replaced a lot of sensors but how about tuneup basics?
Plugs, wires, distributor cap and rotor (unless yours is an 00/01), air filter.
You don't have the classic symptoms, but can't rule out fuel injectors either......
 
Oh yea i thought about that after i posted that last nite...it is a 1997 cherokee sport with a 4.0, aw4, dana 30 and 8 1/4, and a homemade air intake and not much else. and there looked to have been a tune done on it not too long before i bought it, but i'm seriously concidering doing it myself to install some performance goodies on it for more power and torque.
 
Interesting, my 98 was doing something similar but not as bad. I'd been living with it since the jasper engine went in last year. Seemed like a dead spot in the TPS to me but it never died, just lost it's nads every once in a while. Fast forward to two weeks ago, alternator went out, replaced the alternator and reconnected the battery, that was after it sat overnite waiting for the alternator. Fired it back up later the next day, went thru the 'ran like crap' for the first half hour and then it relearned. Since then it has not done it. I don't know whether it relearned wrong the first time when the new engine went in and ran like crap or if it was the alternator going bad for the past 11 months. Between the jasper engine going in and the alternator going bad the battery had never been disconnected. Disconnect the battery and let it sit for a couple of hours and then reconnect it, see what happens.
 
moparjim1987 said:
Oh yea i thought about that after i posted that last nite...it is a 1997 cherokee sport with a 4.0, aw4, dana 30 and 8 1/4, and a homemade air intake and not much else. and there looked to have been a tune done on it not too long before i bought it, but i'm seriously concidering doing it myself to install some performance goodies on it for more power and torque.

I recomend fixing your problem first before you "install some performance goodies on it for more power and torque".

Relearning the computer is a good idea.
So is checking cap/rotor/plugs.
Check ground staps from engine to frame/firewall.
How are the battery connections?

Is it flashing the Check engine light.
Have you checked to see if it is throwing any diagnostic codes?
Sometimes the PCM will throw a code, but not light the check engine light. It would be interesting to know what the PCM thinks is going on. Get a cheap reader.

Something which happened to me:
I had a bad O2#2 sensor (smashed it against the floor) and it popped the O2 heater fuse. The rig would run a bit rich at first (burp it and it would be fine again), until the engine temp reached the switchover spot from Open Loop to Closed Loop, then it would want to die until the O2 sensor got warm enough to get the mixture right. It wouldn't always light the CEL, but would always throw a code because the heater is supervised. So checking the codes is something you may want to start with instead of throwing parts at it.

Good Luck!
 
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