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89 Not Running

B

brandonmcnulty

NAXJA Forum User
Location
Arkansas City, Kansas
I have an 89 Jeep comanche with the 4.0 auto and it wont hardly idle at all now, i start it and it idels good for about 5 seconds then idles really low. I can give it gas and it will try to rev up, most of the time it dies. But if it does rev up it backfires through the intake and sometimes through the exhaust. I have replaced the fuel injectors, the fuel filter, plugs and wires. I dont know what else to change except the o2 sensor. But i unplugged it and it still did the same thing. I also tried searching the site about the tps but came up short.

Any help is appreciated
Brandon
 
try disconnecting the vaccume line to the egr valve
 
hay dude it sounds like fuel pump proublems. the back fire is a lean pop. try some carb cleaner in the throttle body when starting motor and see if it starts up then continue to spray on an off when throttle up if this works check your gas line for kinks or leaks if none drop gas tank good luck let me know
 
I checked the fuel pressure yesterday and had 32 lbs at idle then i shut it off and started checking other things. I replaced the fuel filter and plugs and wires. But i checked the fuel preesure today. I think i hooked it up the same and its reading about 25 lbs at any rpm and when i unhook the vacuum line from the round thing at the front of the fuel rail it also stays the same. The only time i can get the gages to move is when the truck dies and then it falls to about 10lbs. Are my gages working right and my fuel pump it bad? I figured the pressure would go up when the rpms where higher. But according to my gages it doesnt but the truck will run semi good when i rev it up.
 
Hay dude a good diag. of what your engine is doing is to trust your tools if it said 10lbs then YOU NEED A FUEL PUMP not a new guage Also quit wasting you money on plugs and wires when your proublem is fuel try the carb cleaner. I have 30 years training in this feild and trust something let me know if it works
 
brandonmcnulty said:
I checked the fuel pressure yesterday and had 32 lbs at idle then i shut it off and started checking other things. I replaced the fuel filter and plugs and wires. But i checked the fuel preesure today. I think i hooked it up the same and its reading about 25 lbs at any rpm and when i unhook the vacuum line from the round thing at the front of the fuel rail it also stays the same. The only time i can get the gages to move is when the truck dies and then it falls to about 10lbs. Are my gages working right and my fuel pump it bad? I figured the pressure would go up when the rpms where higher. But according to my gages it doesnt but the truck will run semi good when i rev it up.
Click to expand...
 
See the reason i thought that my gages werent "qualified" for the job is that they are R-12 charging gages.. But they hooked up to the shrader valve and gave me a reading. Im just trying to double check because a new fuel pump is a little pricey for a guy still in high school making min wage. I needed new plugs and wires any way. I have put about 40K on this truck and i never changed them.
Brandon
 
I had the same problem with my 89 4.0 and replaced the fuel pump, o2 sensor and did a full tune. Come to find out it was the air intake sensor causing all the problems. It was pretty much melted, cleaned it up and it ran alright. Ordered a new one from autozone, not a stock part. cost me like $27 with the shipping. Probably didn't need the fuel pump or o2 sensor but they go at like 90,000 anyway. for the record, my jeep is a 89 cherokee laredo with aw4 and 4.0
 
Go back and check your fuel pressure. ALways start basic and then get precise.
BSD
 
rechecked my fuel pressure. I can hook it up and turn on the key and i read 10lbs when i start it up it shoots up to about 26lbs but never get off it unless it dies. when i rev it up, which is hard to do becuase it wants to die the gage wont move. So im guessin its my fuel pump. Called the parts store 81 bucks for the pump and 5 for the strainer. Wew i hope this makes my jeep run. Then after this im gonna replace my 02 sensor to get some better gas mileage(ive been get about 11) so hopefully this will help. But i need to get her runnin before i think about gas mileage.
thanks alot
BRandon
 
The pressure is out of specs. One thing I migth caution, I am unsure what you checked your pressure with. I am no engineer, but I wonder if a gauge meant to measure gas pressure will work teh same as one meant to measure fluid pressure. Others with more knowledge might contribute on this. Also, change your fuel filter while you are at it.
BSD
 
BSD said:
The pressure is out of specs. One thing I migth caution, I am unsure what you checked your pressure with. I am no engineer, but I wonder if a gauge meant to measure gas pressure will work teh same as one meant to measure fluid pressure. Others with more knowledge might contribute on this. Also, change your fuel filter while you are at it.
BSD
Click to expand...
PSI is PSI gas or fluid.
 
langer1 said:
PSI is PSI gas or fluid.
Click to expand...
I thought so but thought I would err on teh side of caution. Thanks for confirming. I guess my hesitancy revolved around wether a fluid and a gas had different dynamics in exerting pressure. Thanks
 
BSD said:
I thought so but thought I would err on teh side of caution. Thanks for confirming. I guess my hesitancy revolved around wether a fluid and a gas had different dynamics in exerting pressure. Thanks
Click to expand...
Don't over think it.
Most of the time the fluid never reaches the gauge anyway.
 
alright replaced fuel pump today. And now she runs. IM glad i got this fixed. BUt now she idles about 2 grand. I think its becuase i was messing with the TPS. But i have adjusted it. and i have came up with this. When i have the TPS pushed all the way down it idles lower but spudders when i step on the gas and backfires. When it is all the way up it idles at about 2 grand when started and if i rev it up it stays there until i shut it off and restart it. The idle isnt a big deal but if im driving it and i give it more than half throttle it bogs down. The same thing it did back when i started having problems. I dont really know what the prob could be except my TPS. I have changed fuel pump and filter. PLugs wires and cleaned the throttle body and IAC and checked my spark. the only thing i think i have left is the TPS. Is there somthing else i have to do to adjust it?
 
brandonmcnulty said:
alright replaced fuel pump today. And now she runs. IM glad i got this fixed. BUt now she idles about 2 grand. I think its becuase i was messing with the TPS. But i have adjusted it. and i have came up with this. When i have the TPS pushed all the way down it idles lower but spudders when i step on the gas and backfires. When it is all the way up it idles at about 2 grand when started and if i rev it up it stays there until i shut it off and restart it. The idle isnt a big deal but if im driving it and i give it more than half throttle it bogs down. The same thing it did back when i started having problems. I dont really know what the prob could be except my TPS. I have changed fuel pump and filter. PLugs wires and cleaned the throttle body and IAC and checked my spark. the only thing i think i have left is the TPS. Is there somthing else i have to do to adjust it?
Click to expand...

check this

http://www.wagoneers.com/XJ/tech/TPS-adjustment.html
 
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