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bucking jeep yee ha

evrydayXJ

NAXJA Forum User
Location
Lincoln, Ne
the jeep is buckig almost like it is misfiring yet i pull the plugs when it is runnign and it runs worse with each plug removed the codes its throwing according to key method only 35 which is cooling system. and it is my fault due to way fans are wired.. jumped from relay in pdc. and than 42 which is asd? i need help i am broke right now and don't want to throw parts at it. its a 94' 4.0 ax-15
thanks in advance
 
i tested the fuel pressure at 31 psi and when disengage the vaccum i get 39 psi. which is what it needs to be i believe correct me if im wrong. i tested the fuel injectors and i get 15-15.6 resistance the highest is in the front? i would assume this is because they get hotter in the front of the motor? i cleaned the throttle body was pretty black but all clean now, i pulled the air temp sensor and it was also gumed up so i replaced (23.00$) lifetime warr. so i don't believe i have a fuel problem. when i pull the plug wires it does not fade anyworse between each wire. the "misfire" is still there. im calling it a misfire because that is how it seems not because i know this. im not sure how to test the tps or the cps. if anyone knows or have any info at all pease pease chime in. this is holding me back from wheeling so please help. it is progressivly getting worse day to day, this has been going on four about 8 days. also i replaced the fuel filter about a month ago, plugs, wires, cap, rotor about 8K ago.
thanks
dan
 
Is there any autozone near you? Id say go there and have them scan it in case you messed up on the flash method or whatever you want to call it. Does it buck all the time? Driving normally, when letting off the clutch pedal?
 
the codes i gave were from a very nice scanner at my friends mechanics shop. and it does it most at about 1500-2500 rpm, seems as if it is cutting out or mis firing something to cause a slight jerk, don't see the rpm drop if they do it is minimal and it ides ok? but you can hear it mis after it goes through the order.
 
i would really like to know how to check for tps and cps to see if they are the culprit i have done lots of searching on here and no one has the "same" problem alot of people have same problem but also no start issues and with automatics with torque converter bolts being loose
 
It sounds like it's only happening under a load? I had an issue simalir to this years ago in my old XJ. Mechanics couldn't reproduce it while it was hooked up to the diognostic scanner.

It ended up being a fuel pump return line inside of the tank. I don't know if that helps but it's worth a look if your tank is low. It caused the drop in pressure only when driving it.
 
thanks i was actually going to drop tank and clean it out just bc jeep has 16?000 on the clock and its time for it and im out of work right now.
thanks for the input how did they finally fix it? what made them check that?
and yes your correct actually the problem is getting worse, it happens most 3 and 4 gear and about 1800-2500 rpm i have done fuel pressure check and it was 31psi and 39 with vac line pulled.
dan
 
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