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Unread 01-13-2014, 05:10 PM   #1
torchd
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1998 ZJ 
 
Join Date: Jan 2010
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Jeep Starting To Randomly Stall, Buck and Hesitate

About 2 weeks ago my Jeep stalled coming to a stop light didn't think much of it. Now since that first time, it is starting to die/stall more and more.

Sometimes when coming taking from a stop sign it'll hesitate or buck. I have now CEL so it's not misfiring...

What could possibly be doing this? Tonight sitting in a parking lot, Jeep just shut off for no reason. I started it back up ran for 3 seconds then died again...


Possible causes:
Bad injector - been running 703s since 7/2012

Tune Up- currently running Kolak's ignition set up (MSD ignition cool, magnecore wires, autolite plugs cap/rotor can't remember the name)

Bad fuel filter/pump- fuel filter is inside the fuel tank. Maybe it's clogged? Fuel pump starting to go out

Dirty IAC- clean at least twice a year


So what else can be causing my random stalking, hesitating and bucking??

Any help would be greatly appreciated!!

__________________
[b]1998 Jeep Grand Cherokee Laredo[/b]
2" BB Pucks | SkyJacker Hydro Shocks | Rubicon Wheels | Cooper 245/75/16 Tires

[b][color=red]2002 Trans Am[/b][/color]
Cam, Full Exhaust, Stock Heads, Stock LS6 Intake and Stock 10 bolt with 3.42s
[b]420 RWHP and 382 RWHTQ[/b]
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Unread 01-13-2014, 05:13 PM   #2
PolkaPower
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Tps
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Unread 01-13-2014, 11:57 PM   #3
rep-tile
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^^ what he said.

Another possibility is you have loose or corroded battery cables. If you see any signs of corrosion, clean them up. Voltage fluctuations can cause the PCM to act up.
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Unread 01-14-2014, 01:25 AM   #4
torchd
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Cables are clean. I clean them regularly.

How can I tell if the TPS is going bad? I guess I can look at replacing it. What is the cost of a new one?
__________________
[b]1998 Jeep Grand Cherokee Laredo[/b]
2" BB Pucks | SkyJacker Hydro Shocks | Rubicon Wheels | Cooper 245/75/16 Tires

[b][color=red]2002 Trans Am[/b][/color]
Cam, Full Exhaust, Stock Heads, Stock LS6 Intake and Stock 10 bolt with 3.42s
[b]420 RWHP and 382 RWHTQ[/b]
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Unread 01-14-2014, 06:22 AM   #5
PolkaPower
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You can test it with a multimeter. When mine went bad it acted like it would stall, bucked, sudden loss of power. Not real fun when you go to pass on the highway.
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Unread 01-18-2014, 08:05 AM   #6
torchd
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Jeep was fine for a couple days. Yesterday sitting, I was waiting for a train, I had the tranny in N and out of nowhere Jeep just shut off...

Started it back up. Upon starting back up, you could hear a pop-back fire from the exhaust.

Now what causes a back fire? Too much fuel? Are my 703s going bad?
__________________
[b]1998 Jeep Grand Cherokee Laredo[/b]
2" BB Pucks | SkyJacker Hydro Shocks | Rubicon Wheels | Cooper 245/75/16 Tires

[b][color=red]2002 Trans Am[/b][/color]
Cam, Full Exhaust, Stock Heads, Stock LS6 Intake and Stock 10 bolt with 3.42s
[b]420 RWHP and 382 RWHTQ[/b]
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Unread 01-18-2014, 08:21 AM   #7
ZeeJay1997
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Quote:
Originally Posted by torchd View Post
out of nowhere Jeep just shut off...
Quote:
Originally Posted by torchd View Post
So what else can be causing my random stalking, hesitating and bucking?
when mine was doing this, i spend about 700 bucks before i figured out it was the PCM.

see link below
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Unread 01-18-2014, 10:25 PM   #8
rep-tile
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Stalling and hesitating because TPS affects air/fuel ratio, bucking because TCM receives input from TPS to make shifting decisions. Not a certainty, but based on your symptoms, it is the most likely culprit, and TPSs have the tendency to go bad. Test it with a voltmeter to confirm. Stay away from part stors sensors, go dealer only.
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Unread 01-18-2014, 10:59 PM   #9
scope513
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My advicebcause I have/had the same problems is the pcm...ive changed idle air control valve, tps, map sensor, crankshaft sensor distributor cap etc. You can do that if you have yhe money cause changing sensors and idle air always helps or tou can just clean up the idle air control valve..but 85 percent of yhe time its the pcm..zip tie it or losen the bolts two complete turns depending on year..no money..see if that works first.
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Unread 01-20-2014, 02:34 PM   #10
torchd
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Just for the hell of it, today I seafoamed the motor and really cleaned the IAC. I am leaning towards that the CPS is going bad....

I really hope it isn't the PCM...
__________________
[b]1998 Jeep Grand Cherokee Laredo[/b]
2" BB Pucks | SkyJacker Hydro Shocks | Rubicon Wheels | Cooper 245/75/16 Tires

[b][color=red]2002 Trans Am[/b][/color]
Cam, Full Exhaust, Stock Heads, Stock LS6 Intake and Stock 10 bolt with 3.42s
[b]420 RWHP and 382 RWHTQ[/b]
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Unread 01-20-2014, 10:39 PM   #11
torchd
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For some reason YouTube will not lids the videos from my phone. I'll have to do it tomorrow.


Well ever since I seafoamed my motor and cleanedmy IAC I've had a couple of issues.


Now the Jeep idles really low
Jeep has a bit of an idle surge now


This is where the Jeep idles now. Used to be right at 500 RPMS. Now it is lower



Jeep Low Idle On Start Up



Jeep Idle Surge
__________________
[b]1998 Jeep Grand Cherokee Laredo[/b]
2" BB Pucks | SkyJacker Hydro Shocks | Rubicon Wheels | Cooper 245/75/16 Tires

[b][color=red]2002 Trans Am[/b][/color]
Cam, Full Exhaust, Stock Heads, Stock LS6 Intake and Stock 10 bolt with 3.42s
[b]420 RWHP and 382 RWHTQ[/b]
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Unread 01-20-2014, 10:52 PM   #12
scope513
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Thats about normal..
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Unread 01-20-2014, 11:29 PM   #13
Oldfrog
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Quote:
Originally Posted by scope513 View Post
My advicebcause I have/had the same problems is the pcm...ive changed idle air control valve, tps, map sensor, crankshaft sensor distributor cap etc. You can do that if you have yhe money cause changing sensors and idle air always helps or tou can just clean up the idle air control valve..but 85 percent of yhe time its the pcm..zip tie it or losen the bolts two complete turns depending on year..no money..see if that works first.
The zip tie thing is a band aid, and wont cure it for long and the screws thing is a hoax. Those two screws dont touch anything on the back side.

Before you run out and buy sensors, go through Zeejay's list:
http://www.jeepforum.com/forum/f13/1.../#post14045654

That said, try unplugging the upstream o2 sensor connector ( near the exhaust collector pipe) and run it for a little while. It will throw a CEL, but it could be shorted out, causing your PCM to act stupid. If so, then replace it with an NTK brand ONLY. Bosch o2 sensors dont work well in Jeeps.

If at some point you determine that it's a crank sensor ( CPS), then install ONLY a Mopar sensor.

Here's what's happening when it runs for 3 seconds and dies:
The PCM is looking for a crank sensor signal, as well as signals from the TPS, IAC, Temp sensor and Cam sensor ( in the distributor). If it doesnt get what it wants, it activates the autoshutdown relay after 2-3 seconds. The crank sensor is especially important during this process. But that doesnt mean your CPS is bad. It could be a bad coil, bad sensor ground ( below the coil) , bad alternator, wiring....or even low trans fluid. ( atf+4)

Go thru the list and perform the tests. Many of us have been thru this who ordeal. I've had 5 PCMs...and think a bad o2 sensor fried 2 of them. Good luck !
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On 7th PCM. Finally got a good one.

Stalling? Work through Zeejay's list

God Bless the Garland, TX Police Dept.
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Unread 01-21-2014, 03:37 AM   #14
torchd
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Posts: 2,561
Low Idle


Idle Surge
__________________
[b]1998 Jeep Grand Cherokee Laredo[/b]
2" BB Pucks | SkyJacker Hydro Shocks | Rubicon Wheels | Cooper 245/75/16 Tires

[b][color=red]2002 Trans Am[/b][/color]
Cam, Full Exhaust, Stock Heads, Stock LS6 Intake and Stock 10 bolt with 3.42s
[b]420 RWHP and 382 RWHTQ[/b]
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Unread 01-21-2014, 03:40 AM   #15
torchd
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1998 ZJ 
 
Join Date: Jan 2010
Location: Chicago
Posts: 2,561
My Jeep barely wanted to idle this morning the surge was son bad. It was well below 500 RPMs and dipping to 0 RPMs....


So anyone, what can this be. This all happened after I was done cleaning my IAC and seafoamed the motor. Both I've done countless number of times and never had this problem before.

So what is messed up now?
__________________
[b]1998 Jeep Grand Cherokee Laredo[/b]
2" BB Pucks | SkyJacker Hydro Shocks | Rubicon Wheels | Cooper 245/75/16 Tires

[b][color=red]2002 Trans Am[/b][/color]
Cam, Full Exhaust, Stock Heads, Stock LS6 Intake and Stock 10 bolt with 3.42s
[b]420 RWHP and 382 RWHTQ[/b]
torchd is offline   Reply With Quote Quick reply to this message
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