Head scratcher with a 1998 Grand Cherokee - JeepForum.com
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post #1 of 15 Old 09-12-2021, 09:49 AM Thread Starter
IndyGunsmith
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Head scratcher with a 1998 Grand Cherokee

Good morning all!


I'm new to the forum, and I don't want to be that guy that joins just to ask a question....but here we are :-D


I have a head scratcher that I cannot figure out. I have a 1998 Jeep Grand Cherokee that was my great uncles. It has 337k miles (yes that's correct!) but it has been babied! When he passed away, I got it to drive. It had sat for a while, but a new battery, and it fired right up!



I drove it around for a while, but then it started randomly dying. I was told to replace the Idle Control Valve, which I did. Didn't work...so then I was told several other things...here's what I have done:


Idle Control Valve
Throttle Position Sensor
MAP Sensor
Injectors
Coil

PCM
Crank Position Sensor




It is still idling irregularly, and it will occasionally stall out.



Prior to me getting it, it received new plugs, cap, rotor and wires.



Any suggestions?



It is not throwing any codes.

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post #2 of 15 Old 09-12-2021, 10:40 AM
yjsaabman
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I'd start by checking all the ground connections and wiring for cleanliness and condition. Bad grounds can wreak havoc on electrical systems with no faults or patterns.

I'd also be looking at the fuel system. Test the fuel pressure, especially when it's giving you issues. 337k miles is more than a lot for a fuel pump. Not sure if the 98 still has an external fuel filter, but if it does it would be worth changing, too.

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post #3 of 15 Old 09-12-2021, 11:58 AM Thread Starter
IndyGunsmith
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Quote:
Originally Posted by yjsaabman View Post
I'd start by checking all the ground connections and wiring for cleanliness and condition. Bad grounds can wreak havoc on electrical systems with no faults or patterns.

I'd also be looking at the fuel system. Test the fuel pressure, especially when it's giving you issues. 337k miles is more than a lot for a fuel pump. Not sure if the 98 still has an external fuel filter, but if it does it would be worth changing, too.

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I should mention that I did check ALL connections, cleaning them, and reinstalled ALL of them. That took some time! I've checked ground, and even used a multimeter to test ohms. No luck!

I'll go the fuel route. Pressure seemed good when checked, but I am at a loss. I'll try anything!

Pumps and regulators aren't terribly expensive. Just time consuming replacing.
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post #4 of 15 Old 09-12-2021, 12:14 PM
jm8881
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I had what seems like your same problem and it turned out to be a wiring issue before the coil. There was a "repair" done to the wires about 8 inches before the coil plug. It was a unique issue for sure but it would be worth looking into.
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post #5 of 15 Old 09-12-2021, 12:37 PM Thread Starter
IndyGunsmith
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Quote:
Originally Posted by jm8881 View Post
I had what seems like your same problem and it turned out to be a wiring issue before the coil. There was a "repair" done to the wires about 8 inches before the coil plug. It was a unique issue for sure but it would be worth looking into.

It's worth a second look!!! Thanks!!!
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post #6 of 15 Old 09-12-2021, 01:05 PM
RedRiverT
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Here's the ol' standard process that has worked for many over the years:
https://www.jeepforum.com/forum/f13/...talls-1407423/

There is another thread where the guy claims that another problem is that the electrical contact tans in the PCM connector plugs lose their springiness and lead to failing connections (or something like that):
https://www.jeepforum.com/forum/f13/.../#post15071349

There are a couple of other little quirks and I don't remember if they're mentioned in the "12 steps" thread. They probably are.
-I don't know if it's a "common problem" but several people have reported a failure of the wires just outside the distributor.

-Also, inside the little black plastic box behind the battery, the Power Distribution Center (PDC), those electrical connections can become corroded, both the power wires and the blades on the fuses and relays.

-The battery cables can corrode back up inside the insulation and the wires rot away, causing power fluctuations and shutting off the PCM.

-Here's a common one: the wires to one of the oxygen sensors in the exhaust pipe burn through against the pipe, maybe sometimes being blown up against the pipe randomly, and cause it to die.

-There can be a worn-through spot on a wire somewhere in the engine bay and it might move enough to hit metal and short, causing the PCM to shut off. I thought I had a YouTube link saved of a mechanic diagnosing one of those, but apparently not.

Your fuel pump, filter and regulator are all combined in the pump "module". The regulator and filter are in the little silver metal canister on top. That canister can be changed by itself, but it's nearly just as easy and not a whole more expensive to change the entire pump module. I was in a mode of "I'm not spending a dime more than I have to on this cheap transportation zj", and was having a bogging down problem that led to noticing fluctuating fuel pressure, so I tried buying $30-something filter/regulator cans off of eBay or somewhere and the first failed quickly, then they sent me a replacement and it was apparently bad out of the box, then they said they would send another if I sent it back, but they never did, and they didn't reimburse the return shipping for either one. I bought a name brand one from Autozone for nearly $90 and it has worked fine. An entire pump module was <$150 then, and I wouldn't have had to drop the tank 3 or 4 times.
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post #7 of 15 Old 09-12-2021, 01:50 PM
jtec
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thoughts-
you are checking for codes don't assume no light no code.
Check fuel pressure with a gauge, post PSI.
Does it stall driving - accelerating, idling, braking?
Dash lights when acting up - on or staying off till eng quits?
Any added - alarm, remote starter, kill switch?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #8 of 15 Old 09-13-2021, 07:07 PM
Titnado1
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Garage
You replaced the IAC valve but did you clean the throttle body that it seats on? it may be really crapped up and sticking. and it was mentioned but yeah scan the codes mine cel never came on and had 2 codes. would have never known if I didnt scan it

If you can drive it, fly it, or bang it.... rent it.
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post #9 of 15 Old 09-15-2021, 09:44 AM Thread Starter
IndyGunsmith
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Originally Posted by Titnado1 View Post
You replaced the IAC valve but did you clean the throttle body that it seats on? it may be really crapped up and sticking. and it was mentioned but yeah scan the codes mine cel never came on and had 2 codes. would have never known if I didnt scan it

Throttle body was cleaned! Took it off and put it in my ultrasonic parts washer.



Computer is not throwing any codes. I hooked it up to my scanner and no codes were present.
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post #10 of 15 Old 09-15-2021, 03:08 PM
riiz
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Did you use Mopar Sensors/Solenoids?
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post #11 of 15 Old 09-18-2021, 08:17 AM
LittleFootZJ
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Head scratcher with a 1998 Grand Cherokee

Not sure if anyone has mentioned it yet but I had this issue and it ended up being the routing of the wires off of the distributor. Make sure they are routed the way it says in the service bulletin for the 5.2 magnum motor. I think I found a link to it in this forum somewhere but the wires need to be over and under each other a certain way or it can cause stumbling and misfires and in my case it actually caused it to stall out randomly at idle or start and immediately die.


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post #12 of 15 Old 09-18-2021, 02:36 PM
yjsaabman
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Quote:
Originally Posted by LittleFootZJ View Post
Not sure if anyone has mentioned it yet but I had this issue and it ended up being the routing of the wires off of the distributor. Make sure they are routed the way it says in the service bulletin for the 5.2 magnum motor. I think I found a link to it in this forum somewhere but the wires need to be over and under each other a certain way or it can cause stumbling and misfires and in my case it actually caused it to stall out randomly at idle or start and immediately die.


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The spark plug wires, yes. Some GM cars are the same way, they don't like the wires to be crossed over. Says to me lousy insulation in the wires themselves, but brand of wires doesn't seem to matter.

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post #13 of 15 Old 09-19-2021, 06:16 AM
V8GCZJ
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What motor? If it's 5.2/5.9 the plenum gasket is an issue. With that many miles you may have a lot of blow by. Have you checked compression? When you say "die" does it shut off while driving at rpm or die when off the throttle?
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post #14 of 15 Old 09-20-2021, 07:16 AM Thread Starter
IndyGunsmith
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Good morning!


After lots of checking and rechecking, I have found the fuel pump is going out. It's doing the long crank problem. I cycle the key on and off several times, and then it starts up. It runs a little rough in the beginning, then it evens out. I haven't had any issues with it dying for a while, since the PCM was replaced. I think once the fuel pump assembly is replaced, I should have the problem fixed...I think.


However, I am going to try and do what everyone else has recommended. It doesn't hurt!


It's a 4.0L inline 6...I don't know how many more miles I'll get out of it, but I've been lucky thus far!
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post #15 of 15 Old 10-17-2021, 10:57 AM Thread Starter
IndyGunsmith
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Wanted to follow up with this:

I replaced the fuel pump recently. The old fuel pump was BAAAAD....Honestly I don't know how the thing was running. Since replacing, I have not had a single issue. It starts, runs, drives great! I even get 20 mpg now...which is a huge difference from the 16-16.5 mpg I was getting. And with gas around these parts at 3.40 and up a gallon, I'll take every MPG I can get!

Thanks everyone for your help and suggestions! Hopefully, I can return the favor one day!
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