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Unread 06-26-2012, 10:08 PM   #1
jamesh23
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1994 ZJ 
 
Join Date: Feb 2012
Location: pueblo, co
Posts: 51
98 4.0 wont stay running help?

alright this thing gives me problems then runs like a dream, followed by more problems lol, so heres my current issue

oh ya its a 1998 grand cherokee 4x4 4.0 202,000 miles
new parts within 1500 miles
plugs, wires, cap, rotor, coil seafoamed
crank position sensor
throttle position sensor
coolant temp sensor on thermostat housing
new battery terminals
all grounds cleaned
downstream o2 sensor
fuel pump relay
couple new fuses

have also sprayed brake clean around carb cleaner and manifold to check for leaks, no leaks were found.

heres my issue it happened earlier today keep in mind with 106 degree temperatures

it started running really rough, I pulled over to get a bite to eat and went to start it and it would fire and immediately sputter out and die, I tried that a couple of times to no avail, waited about 20 minutes and it started up idling really bad again but I was able to drive it to my friends gym, it also died on the road 3 times within about 4 miles,

I worked out and went to leave and it would fire up, than immediately sputter out and die again, I looked around and found that my coolant temp sensor was cracked, so I unplugged it and the jeep started and idled fine for about 20 seconds before I shut it off, and went a bought a new coolant sensor, installed it and hooked everything up and it started up and idled good so I thought problem solved, wrong, it idles good for about 30-45 seconds and than the idle drops and it sputters out and dies...

it continued to do this and somehow I managed to drive it home, it did however die at every traffic light and once on the highway, it runs really rough and drives "jerky" sometimes is the best way I can describe it

I got it home and tried unplugging the maf sensor and it stayed running a little bit longer but still died, I let it run with the MAF unplugged than plugged it back in while it was running and it sputtered some but stayed running and than died a few seconds later... im stumped

I can hear the fuel pump priming as well, so it should be working fine, ill also say that this all started after I almost ran out of gas, made it to the gas station with 2 miles left till empty, I put in $20 of gas and it ran fine, than today its giving me all these problems... idk where to start.

There is also a check engine light, I was going to try and take it to autozone but im afraid it wont make it, I had friend take me to autozone to buy the coolant sensor

also getting really crappy gas mileage, 11 mpg with 31s and no lift with the 4.0


Last edited by jamesh23; 06-26-2012 at 10:41 PM..
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Unread 06-26-2012, 10:31 PM   #2
ozzy_2_me
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Location: Lansing, Michigan
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well for one thing thing you do not want to let your gas tank get below 1/4 tank. this because that gas in the tank acts like a cooling agent for the fuel pump. if you don;t the pump could get hot and die. first thing i would since it hasn't been listed i change out the fuel filter. you have an external fuel filter under neath on the driverside of the frame/support. put more gas in the tank. more then 20 dollars worth. this it what i woudl start with.
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Unread 06-26-2012, 10:42 PM   #3
jamesh23
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I put in another $30 this morning so it has 3/4 of tank now, sorry forgot to mention and all the information on my fuel filter I found was saying that it is inside the gas tank? I believe they made the change for the 98 year? meaning I would have to drop the tank to change the filter?
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Unread 06-26-2012, 10:51 PM   #4
ozzy_2_me
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it should have one inside the tank with the pump and then an inline one on the undercarage. let me get check something really quick and i will et back with you.
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Unread 06-26-2012, 10:59 PM   #5
ozzy_2_me
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well it does look like it is only in the gas tank. i stand corrected. have you cleaned the IAC valve ? these would be next on my list. you alread did the CPS. rules that out.
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Unread 06-26-2012, 11:01 PM   #6
ozzy_2_me
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could possibly need new injectors thats what it took to fix my issue. i had the a similar deal but with the 5.2.
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Unread 06-26-2012, 11:15 PM   #7
phitmein
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What kind of CPS did you put in it ?

Jeeps are very picky about the right ones.
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Unread 06-27-2012, 02:42 AM   #8
jamesh23
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where is the IAC valve located again? and How could I clean it? just brake clean? thanks and sooner or later I believe I will have to drop the tank, but ill be replacing the fuel pump while im in there just to be safe ha

and the CPS Was I believe just a duralast from autozone but I am getting spark and it starts so I thought that would rule out the CPS? I have the stock one still because it turns out it wasnt bad when I replaced it, was just a PITA to put in, I did hear they only like mopar sensors, although I was tight on cash and time as I needed it running asap and at the time the closest dodge dealer was 150 miles away.

thanks for the opinions so far guys keep em coming, this forum has helped me figure out everything thats ever been wrong with it and helped me to do the repairs myself so I have faith in everyone here.
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Unread 06-27-2012, 08:33 AM   #9
Scopez
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IAC is located on right? side of throttle body. Use throttle body cleaner and a toothbrush.
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Unread 06-27-2012, 12:06 PM   #10
jamesh23
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ill clean the IAC today and see if I cant get the jeep to autozone to get the codes pulled, it also backfires a lot through the intake at times when im trying to keep it going by giving it gas? it will still die though
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Unread 06-27-2012, 04:22 PM   #11
xDJxJUSTx
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Wow in that case it seems to me like your timing is off, you might have jumped teeth, time to get out the timing gun
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Unread 06-27-2012, 05:22 PM   #12
flexyxj
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Check your fuelpressure. I think you'll find that the fuelpump is on it's way out. Been there, done that. It is backfiring because it isn't getting enough fuel to run. I had the same exact symptoms with a '93 ZJ. It would idle perfectly and when you put it in gear to take off ,it would spit,sputter and backfire.
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Unread 06-27-2012, 05:23 PM   #13
edpmedic
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Unreal what were they thinking only using a fuel pump filter and not a in line filter. Someone must have been smoking crack at that developers meeting. Or they were so hard up for money due to low sales that they said let's really **** the customer. But from searching in 5 different forums and about 20 thread replies. The same problem your having its related to the fuel pump filter in the tank.
If you let your tank go down and are buying cheap gas this is one of the casualties. I still would clean the IAC . Check the timing also, and put a fuel pump preassure tester on the system. See what's going on, before you drop the tank to replace it.

Is it losing speed once it does run right. Is it back firing when it is running our just when you try and start it due to excessive fuel in the cylinder. Two ways to check for a timing gear slippage. The easiest is to put a compression tester on & see if ALL the cylinders are low and within 5% of each other.

The other way remove plug one get it to TDC on the compression stroke. Make sure the mark on the vibration dampner is at the zero mark at the indicator. See if the distributor rotor is facing the number one wire. Now if you can't judge by just the distributor. You need to remove the valve cover and see if both valves are in the closed position.

That its why I would check fuel pressure. If good clean the IAC if no change compression test and also make sure all your wires are attached, not burnt or arcing before doing the test. If say all cylinders come up at about 75 or 100 psi. I would consider it jumped time. Then I would confirm with the more precise method.

Other things can be the 02 sensor wire is hitting the exhaust and burnt. Or do the ECM connector wire jiggle.

One last thing a vacuum gage its your friend. It may help figure out if it jumped time or restricted exhaust and other things.
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Unread 06-27-2012, 07:47 PM   #14
jamesh23
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went to start it today and it would fire and die the first three times then it started up and as I would give it gas it was backfiring through the exhaust and the intake, I shifted through the gears with my foot on the break and it began idling just fine??? drove it around the block and it drives perfectly normal? its idling as we speak, has been for about 3 minutes but sometimes it stumbles like it wants to die but it wont die? hm im gonna see if I can take it to autozone to get the codes pulled. be right back. I also only use 87 octane in the jeep with half a bottle of injector cleaner when I fill it up.
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Unread 06-27-2012, 08:29 PM   #15
jamesh23
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Location: pueblo, co
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PO108 and PO113

they guy told me it was for intake air temp sensor and mass airflow sensor?

got a can of throttle bottle cleaner and cleaned out the throttle body so far and am working on cleaning the maf sensor and IAC.
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