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2004 Grand Cherokee Laredo

1K views 1 reply 2 participants last post by  Frango100 
#1 · (Edited)
4.0L I6
I just got an Oil Change and Brand new Spark Plugs.

For the last few years I've had it it has always had a slight problem while driving. It would misfire while accelerating around 20-30mph and at around 60-70mph it would misfire again in a series of lurches and the overhead dome would tell me I lost 30-60 miles worth of gas. My mother tried looking at it and getting her friends to look at it but they never came up with any ideas because none of them had any clue when it comes to vehicles. They took a look at the fuel lines and said there was a clog and replaced the tubing about a year ago. I however also don't know much when it comes to vehicles. It hadn't had an oil change in a long while so I got that done as soon as I got it. At first I couldn't drive it a short way down the road without it misfiring and stalling a couple times. Thankfully the shop I got the oil change at was only right around the corner.

I was reading online and trying to take a look at a couple of possibilities but I also don't have the money to just randomly throw parts at it that I really don't need. I Took off the air filter system, and the throttle assembly and Looked at the fuel injectors just to make sure they were working properly and receiving gas, because someone mentioned my Fuel Pump making a noticeable hissing sound. I put the Fuel injectors and the rest back together after cleaning it all off because it was pretty nasty around the area. After that I tried taking out the battery and Pcm because I read that there's a screw or something that causes it to short out on the inside or something. However all my Hex wrenches stripped trying to get the 4 screws out so I gave up an reassembled it. I then Took a look at the spark plugs and noticed they were pretty bad looking, so I replaced them thinking they would solve my misfiring and stalling problem.

I was right.
Or so I thought. Driving it to the auto parts store and back. And then again to the Dollar store and back It didn't act up at all. When previously it would act up as soon as I exited the driveway. Assuming my problem was fixed by resetting the pcm and new Spark Plugs, I decided it was able to drive into town to pick up my younger brother from his new job. It drove fine for about 10miles until randomly sitting at a red light at 11:10pm it stalled as a check engine light came on(other than this instance there is never a check engine light), and then lost all power. I had his girlfriend in the Jeep with me steer while I pushed us into the parking lot and out of the road. After looking at it, I thought maybe it was just the battery, So I loosened the terminals and noticed when I was messing with the negative terminal my hazards would turn on. So thankfully it was just the negative terminal connected to my battery.

We got in, drove the rest of the way to his job and sat in the parking lot with the vehicle running, and after about 2 minutes it stalled once again. I got out and rechecked the terminal and moved and tightened it again. Turned it back over and let it run for a little bit, and it seemed fine. On the way back to the house, it misfires and jerks/lurches while accelerating again, and about 10 miles into our trip, again, it stalls at a red light. I go to turn it back on and it gives me issues until I press the gas with it. It started back up and we continued the journey back to the house.

This morning I took a look at it again and drove it a little bit around the block trying to see if it would do it again but it didn't really give me many issues until I got back in the driveway, where it sputtered and died again. Attempting to restart it it sounded really weak and didn't want to start but without pressing the gas it got around to firing up(on the first key turn) I noticed a weird hissing sound coming from under the hood and noticed that when I put the air filter system back on I didn't tighten a screw all the way, and the whole thing had detached from where the value is that the throttle opens and closes.

Hoping that that was just the issue I experienced last night I reattached it firmly and securely and tried leaving the driveway again to test drive it. Right after my short reverse and braking, prior to putting it into drive to pull forward and out of the driveway it stalls once again. So I put it back in drive and parked it.

As I said I don't have a lot of available funds to waste just throwing parts at it. I would prefer surefire ideas and suggestions as to what I could do to narrow down the true culprit as there are no check engine lights and the only code that gets read with obd is a Hydraulic Pump Circuit Malfunction, which sounds like a dangerous combo with my engine stalling randomly in the middle of the road.

If it's the fuel pump what would I look for to know for sure that it was truly the problem. I read about the Fuel Pump and other relays in the fuse box near the battery and they seemed fine also but I did play musical relays (Swapped them around with the wiper fuses that had the same numerals on them)
O2 Sensor, Egr, The Pcm, Fuel Pump/Fuel Filter, cam/crank shafts? Any other thoughts I should check out to be sure?

Oh, also I read that when it's started and idling it's supposed to sit at around 900rpms but mine sits at around 700rpm, does that make any difference?
 
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#2 ·
Welcome to the garage. I almost fell asleep Reading the whole story:D.
Do you remember what the fault code was which was set? No other codes popped up?
On the 4.0L there is a known issue of a wire bundle which runs at the back of the cylinder head , where it can touch a stud and when the isolation shaves away, cause a short. This typically happens at certain throttle positions, when the torque of the engine moves the engine a bit and can cause the short.
Ofcourse many other possibilities are there, but i would start examinating the wire bundles at the back of the cylinder head very well.
 
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