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Unread 02-24-2012, 01:53 PM   #1
xomby
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2001 Jeep Grand Cherokee 4.0L Stalling

My 2001 Jeep Grand Cherokee 4.0L stalls randomly, both at idle and at speed, with or without load (parked vs. driving). It also has a rough idle (moderate to severe, depending on the temp of the engine - more on that later). NO flashing lights, trouble codes, or intermittent door/window issues.

While I think I've got a good handle on the what and why, I'm putting this thread up in case I DO fix it, in the hopes that it helps someone else down the line (There's so many threads like this out there, but I'm just anal enough to take photos and make notes during the diagnostic/repair process).

Backstory and repairs to date:
The issue started with slight bogging that only lasted a split second, as if I had momentarily taken my foot off the gas pedal. Then progressed to "bogging" for multiple seconds - read as, no matter how much you hit the pedal, it was like the engine/throttle would not respond at all.

I cleaned and reseated the battery terminals, which seemed loose (one was corroded inside the ring, and the other see-sawed on the post, and the car ran fine for a couple of days (computer reset, anyone?).

The last straw was driving fine for 60 miles to a client-site, being there for 6 hours, and then finding that the jeep would NOT start at all. It cranked strongly, but would not start, as if it was out of gas.

Quote:
Note#01 - during this extended period of cranking, I never smelled gas, as though it never flooded - is it not getting gas?
I pulled out the owners manual and dug as much info out of my own memory as I could regarding the various fuses and relays (I also own a '96 with the LEGENDARY electrical issues...) and was relieved to find that most of the relays under the hood were identical. So I swapped relays from not-so-important components to the ones that were (anything related to fuel/engine electrical) - fuel pump, TCM, etc. and that did absolutely nothing. (I tried starting between swaps, hoping to find an issue - no such luck).

I then moved on to the few fuses under the driver-side dashboard that had anything to do with ignition/electrical, but found nothing that screamed "I'm the problem" there either... But after checking all of the fuses that seemed to matter, the car actually started.

Quote:
Note#02 - Odd smell coming from the engine here, not quite an electrical burning, sort of "hot" and "sweet" smell - like gasket glue, sort of.
Let the car warm up and idle a bit - as I figured the battery probably could use a bit of charging after all of that cranking - and took off towards home. Car seemed to be running a little rough, but otherwise fine.

Stopped at a red light and it promptly died. Fired right back up, though. Took off at the green and went up a hill with the usual exuberance, but coasting down the other side I felt it bog and almost stall again. Needless to say I "two footed" it the rest of the way home.

Quote:
Note#03 - Seems like it only stalls when idling/foot off accelerator - could be Idle Air Controller Valve
I found that the pintle (the mushroom shaped appendage) on the idle air controller valve would spin easily with just two fingers, and seemed to catch and then release, much like a stripped screw, so $80 later I had a new one of those.

When I put the new unit in, however, the jeep would NOT start at all, again, just like the last time (I vaguely recall something like this happening with my '96 when I put a new IAC in, but I'm not positive). Did the same series of checks on the relays and fuses and still could not get it to start.

Quote:
Note#04 - I can hear the fuel pump running, and cutting out when it's supposed to if you don't start the car, and the tell tale click under the hood that corresponds (I think) with the fuel pump relay turning off.
Exasperated after fighting with the torx screws that holds the IAC on, I put the old IAC (that I'm 100% sure is damaged) back on and the car fired back up after just a couple of tries. Put the new IAC back on immediately and the car started on the first shot.
Quote:
Note#05 - there's that funny smell again - almost reminds me of ether or maybe Gumout burning off after cleaning the engine, but I've never used either of those on this vehicle.
Everything seemed fine and the car ran ok (idle was better after the cleaning) for a couple of days.

Today it stalled 4 times on a highway (almost killed me, actually) - and tried to stall 3 times on the back-roads on the way back home.

Following is the list of items I'm going to check tomorrow, I'll come back and edit this and check off those that panned out and those that didn't. If anyone has any other ideas, please feel free to chime in!

1. Check voltage at PCI bus wire.
Quote:
The PCI Bus wire is either yellow with a violet tracer, or white with a violet tracer, depending on year and model. If the volt reading is zero, or very close to zero, it is possible that the PCI bus is OPEN, or SHORTED TO GROUND. A different test will be required, which is detailed later in this article.

If the volt reading is close to 12 volts, or battery voltage, the PCI Bus is shorted to voltage, and diagnosis should be fairly easy.

If the volt reading is varying between 0.5 and 2.5 volts, the fault is not present at this time. Verify this by inspecting the operation of the windows and other symptoms.
2. Check wire harnesses and bundles for signs of wear or arcing/grounding
Quote:
Specifically:
A. The battery wires as well as the alternator wires that are wrapped up with them directly off the side of the battery.
B. The neutral safty switch wireing that is run over the top of the transmission from passenger to driver side may be tightly pulled against the housing and bracketry for the shifting cables. this could wear through just enough to cause a sort.
C. Wires just above the passanger strut bolt that could be worn through. These wires were to include the famous "earth wire" which may also show signs of abuse.*
D. One other place (under the hood) was the wireing on the driver rear of the engine may also have some damage.
E. the wires at the end of the fuel injector strip
3. Backprobe and test the crank position sensor (possibility)

4. Check ECM connectors (this was ONE of the MANY issues on my '96 gc)

Thanks for feedback/advise/encouragement!

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Unread 02-24-2012, 02:28 PM   #2
Millermagic
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Crank Sensor?
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Unread 02-24-2012, 05:52 PM   #3
CJ7-Tim
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You said Grand Cherokee, right ? The following is XJ Cherokee info, but probably applies to Grand 4.0L's also.

Consider the possibility you have multiple, and unrelated issues.

Are all you tune-up parts fresh ? Used some fuel injector cleaner recently ?

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Do the same for the grounding wires from the starter to engine block, and from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds and the ECM/ECU may behave oddly until you remedy

Cranking and not starting is usually the CPS. The CPS may test good, until it fails and you stall.

#3 Seems like it only stalls when idling/foot off accelerator. Symptoms of low voltage.

The most likely cause of it cranks and cranks but won't start up is the Crankshaft Position Sensor (CPS) located on the transmission bell housing. Often this part is also referred to as the Crankshaft Position Sensor (CKP) CPS/CKP failure is very common. The CPS/CKP can stop working with no warning or symptoms and the engine will not run or the engine may randomly stall for no apparent reason.

Typical Symptoms –
- Starter cranks and cranks but engine won't start up and run.
- Fuel gauge and voltage gauge may not work or display properly.
- You sometimes will have No Bus on the odometer after 30-60 seconds.
- A failed CPS/CKP may or may not throw a CEL trouble code.
- No spark at the spark plugs.
- Fuel pump should run and prime for 3-5 seconds.

Exchange the fuel pump relay and the ASD relay with one of the other similar ones in the PDC to eliminate the relays as the cause of the no-start. Check the ASD relay fuse.

Confirm that the fuel pump to runs for 3-5 seconds when you turn the ignition key to ON.

Eliminate the NSS as a cause of no start. Wiggle the shift lever at the same time you try to start. Put the transmission in Neutral and do the same. Do the reverse lights come on when the shifter is in Reverse?

Inspect the wires and wire connectors at the O2 sensors on the exhausts pipe. A short circuit from melted insulation or from broken O2 sensor wires can blow a fuse and the ECU/ECM will loose communication. Don’t get tunnel vision and assume the sensor is bad (unless it tests bad with a meter). Damaged wiring or a dirty connector can inhibit the signal from making it to the computer. Inspect/test/clean/repair wiring or connectors as necessary.

If the CPS/CKP is failed sometimes the OBD-II trouble code reader cannot make a connection to the ECU/computer or cannot read Check Engine Light/MIL codes because the CPS/CKP has failed. Disconnect the code reader, disconnect the CPS/CKP wire connector, and reconnect the code reader. If the code reader establishes contact with the ECU and scans, your CPS/CKP is failed and needs to be replaced.

Crank Position Sensors can have intermittent “thermal failure”. This means that the CPS/CKP fails when the engine gets hot, but works again (and will test as “good”) when it cools back down.

Diagnostic steps to confirm the CPS is the cause of your no-start

1) You should be able to verify a bad cps, by unplugging it, and turning the ignition key to on. If the voltage gauge and/or the fuel gauge now display correctly and/or the No-Bus is gone, replace the CPS.

2) If the CEL does not come on when the key is turned to the RUN position... then the CPS/CKP is bad.

3) Unplugging and reconnecting the CPS sensor where it connect to the main harness near the back of the intake manifold usually resets the ECU and if the jeep fires right up after doing this you can bet that the CPS is faulty and needs to be replaced.

The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector is near the Transfer Case, not as shown in the diagram below. Simply follow the wire from the sensor to the connector.


CPS Testing

Crankshaft Position Sensor Connector (CPS/CKP)


.


TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (See Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.
.

.



PCM reboot

For 1996+ Jeeps, the OBD-II engine computer (ECU/PCM) re-boots, and the idle settings are deleted, when you: (1) let the battery run down by leaving the lights or radio on, (2) disconnect the battery for an extended period of time, (3) when the battery goes bad and needs replacing, (4) when the alternator in not properly charging the battery, (5) or when poor battery connections result in a voltage drop at the PCM.



Your symptoms are: (1) having difficulties starting the engine without depressing the gas pedal, and (2) the engine will have a low idle and probably stall unless you keep your foot on the gas pedal. The ECU will relearn the idle settings after a short period of driving and the engine will start and idle normally.

Loose, corroded, or damaged battery cables or ground wires may also cause or contribute to the problem. Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables and replace them as needed. Do the same for the grounding wires from the battery and engine to the Cherokee's frame/body.

If the symptoms reoccur, you need to have your battery and/or the alternator load tested at a repair shop or auto parts store. This is usually a free service they offer to bring in potential customers. Even with low battery voltage, the engine will start, but the ECU can re-boot multiple times and a new battery may be required.


Cleaning the Idle Air Controller (IAC), regular tune-ups, and using fuel injector cleaner should be part of your routine preventative maintenance.
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Unread 02-24-2012, 06:00 PM   #4
tjwalker
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Crank sensor is certainly in play here. And if it's an original, I'd get it out of there and replace it with nothing less than an original OEM MOPAR unit. There is a difference in crank sensors. A big difference. There is no better crank sensor than the one you will purchase from your Jeep dealer. And it is not that much more expensive. Well worth it in reliability AND longevity.
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Unread 02-24-2012, 10:25 PM   #5
xomby
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Thanks for the info and ideas!
Quote:
Originally Posted by CJ7-Tim View Post
You said Grand Cherokee, right ?
Yes, that is correct.
Quote:
Originally Posted by CJ7-Tim View Post
The following is XJ Cherokee info, but probably applies to Grand 4.0L's also.

Consider the possibility you have multiple, and unrelated issues.
I have definitely considered this!
Quote:
Originally Posted by CJ7-Tim View Post

Are all you tune-up parts fresh ? Used some fuel injector cleaner recently ?
picking those up in the morning.
Quote:
Originally Posted by CJ7-Tim View Post

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Do the same for the grounding wires from the starter to engine block, and from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds and the ECM/ECU may behave oddly until you remedy
That's pretty much the first thing I'll be doing tomorrow
Quote:
Originally Posted by CJ7-Tim View Post

Cranking and not starting is usually the CPS. The CPS may test good, until it fails and you stall.

#3 Seems like it only stalls when idling/foot off accelerator. Symptoms of low voltage.
makes sense
Quote:
Originally Posted by CJ7-Tim View Post

Typical Symptoms –
- Starter cranks and cranks but engine won't start up and run.
yes
Quote:
Originally Posted by CJ7-Tim View Post
- Fuel gauge and voltage gauge may not work or display properly.
I had this happen on my '96, where crank position sensor made ALL dash indicators non-functional
Quote:
Originally Posted by CJ7-Tim View Post
- You sometimes will have No Bus on the odometer after 30-60 seconds.
I'll be looking very carefully at this one
Quote:
Originally Posted by CJ7-Tim View Post
- A failed CPS/CKP may or may not throw a CEL trouble code.
no codes yet
Quote:
Originally Posted by CJ7-Tim View Post
- No spark at the spark plugs.
I'll check this if applicable
Quote:
Originally Posted by CJ7-Tim View Post
- Fuel pump should run and prime for 3-5 seconds.
This is confirmably working as designed
Quote:
Originally Posted by CJ7-Tim View Post

Exchange the fuel pump relay and the ASD relay with one of the other similar ones in the PDC to eliminate the relays as the cause of the no-start. Check the ASD relay fuse.
did - no issue or change
Quote:
Originally Posted by CJ7-Tim View Post

Confirm that the fuel pump to runs for 3-5 seconds when you turn the ignition key to ON.
yes
Quote:
Originally Posted by CJ7-Tim View Post

Eliminate the NSS as a cause of no start. Wiggle the shift lever at the same time you try to start. Put the transmission in Neutral and do the same. Do the reverse lights come on when the shifter is in Reverse?

Inspect the wires and wire connectors at the O2 sensors on the exhausts pipe. A short circuit from melted insulation or from broken O2 sensor wires can blow a fuse and the ECU/ECM will loose communication. Don’t get tunnel vision and assume the sensor is bad (unless it tests bad with a meter). Damaged wiring or a dirty connector can inhibit the signal from making it to the computer. Inspect/test/clean/repair wiring or connectors as necessary.
I'll be doing this tomorrow, but there are NO blown or even cracked fuses at this point
Quote:
Originally Posted by CJ7-Tim View Post

If the CPS/CKP is failed sometimes the OBD-II trouble code reader cannot make a connection to the ECU/computer or cannot read Check Engine Light/MIL codes because the CPS/CKP has failed. Disconnect the code reader, disconnect the CPS/CKP wire connector, and reconnect the code reader. If the code reader establishes contact with the ECU and scans, your CPS/CKP is failed and needs to be replaced.
code reader hooks up with no issue, but states that there are no codes at all
Quote:
Originally Posted by CJ7-Tim View Post

Crank Position Sensors can have intermittent “thermal failure”. This means that the CPS/CKP fails when the engine gets hot, but works again (and will test as “good”) when it cools back down.
I'll keep an eye out for this one, after I do everything else I'll re-test the CPS at running temp (or as close to it as possible
Quote:
Originally Posted by CJ7-Tim View Post

Diagnostic steps to confirm the CPS is the cause of your no-start

1) You should be able to verify a bad cps, by unplugging it, and turning the ignition key to on. If the voltage gauge and/or the fuel gauge now display correctly and/or the No-Bus is gone, replace the CPS.
non-issue
Quote:
Originally Posted by CJ7-Tim View Post

2) If the CEL does not come on when the key is turned to the RUN position... then the CPS/CKP is bad.
works fine
Quote:
Originally Posted by CJ7-Tim View Post

3) Unplugging and reconnecting the CPS sensor where it connect to the main harness near the back of the intake manifold usually resets the ECU and if the jeep fires right up after doing this you can bet that the CPS is faulty and needs to be replaced.
this will be tough to test, as the stalling is so intermittent
Quote:
Originally Posted by CJ7-Tim View Post

The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector is near the Transfer Case, not as shown in the diagram below. Simply follow the wire from the sensor to the connector.
Thanks for the diagrams - My haynes manual said much the same
Quote:
Originally Posted by CJ7-Tim View Post

PCM reboot
I REALLY want to avoid doing this, as typically it "fixes" the problem for 7-10 days before it comes back... so... but thanks for reminding me!
Quote:
Originally Posted by CJ7-Tim View Post

Your symptoms are: (1) having difficulties starting the engine without depressing the gas pedal, and (2) the engine will have a low idle and probably stall unless you keep your foot on the gas pedal. The ECU will relearn the idle settings after a short period of driving and the engine will start and idle normally.
non-issue
Quote:
Originally Posted by CJ7-Tim View Post

Loose, corroded, or damaged battery cables or ground wires may also cause or contribute to the problem. Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables and replace them as needed. Do the same for the grounding wires from the battery and engine to the Cherokee's frame/body.
already port and polished the battery terminals and connectors, but tomorrow I'll be splitting open the harnesses to look for arcs and damage
Quote:
Originally Posted by CJ7-Tim View Post

If the symptoms reoccur, you need to have your battery and/or the alternator load tested at a repair shop or auto parts store. This is usually a free service they offer to bring in potential customers. Even with low battery voltage, the engine will start, but the ECU can re-boot multiple times and a new battery may be required.
load test came back perfect - for the battery and the charging system
Quote:
Originally Posted by CJ7-Tim View Post

Cleaning the Idle Air Controller (IAC), regular tune-ups, and using fuel injector cleaner should be part of your routine preventative maintenance.
I replaced the IAC (see my original post)
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Unread 07-16-2012, 05:33 PM   #6
piraterig
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did you ever figure this out? im having stalling in reverse only and cant find the issue to save my life.
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Unread 08-25-2012, 04:22 PM   #7
sedition
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i have the same problem. it's incredibly annoying.

after a tune up, new plugs, crank sensor, and a bunch of other stuff i forgot about... it still pulls this crap.
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Unread 09-17-2012, 07:32 AM   #8
01JGC40
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Try Cleaning the Throtle Body
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Unread 09-17-2012, 10:02 AM   #9
buildin1XJ
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From reading your post you have not yet replaced the CPS which could be your problem.Does the jeep allways start with a depressed gas pedal?The reason I ask is that I had one of the many jeeps I have fixed and sold start only with a depressed gas pedal and having lots of extra sensors around I replaced the CPS first no luck,I then swapped in a different TPS and the jeep fired right up and never had another problem.
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