1999 XJ STALLING ISSUE

1999 XJ
4.O
Automatic

The xj will stall intermittently at any speed idle to highway speeds althogh more often at speed. There is no warning no rough idle engine just loses power. This only occurs after the xj has been running for more then 10 or so minutes.The stall is very brief a second or less. If the xj is moving the engine will regain power again, you do not need to restart with ignition the engine regains power on its own. A light flashes on the instrument cluster but it is so brief I can not tell which light it is. At idle the engine will sometimes regain power on its own and at other times will need to be restarted with the ignition. I have checked for codes and none are stored. I have cleaned the battery terminal and checked all grounds pulled and cleaned contact on all fuses and relays in the fuse box on the pasanger side of the engine compartment and still the issue persists. This was a rear occurrence even thought I was imagining it when this first started several month ago but now it is occurring everyday.

Any thought are greatly appreciated.

Could be an early sign of thermal failure in the CKP/CPS crank sensor.

On yours I believe the resistance should be infinite?

There are 3 terminal which do a measure?

Oo-rah

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.

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

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.

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. Jeeps do not tolerate low voltage or poor grounds and the ECM/ECU may behave oddly until you remedy this.



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.

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.


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


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 displays correctly, replace the CPS.

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.

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. 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.


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.

TESTING PROCECURE for 1987 – 1990 4.0 L engines

Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 – 275 Ohms. . If the CPS is out of that range by much, replace it.

Test # 2 - You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.


The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector may be on the passenger side, not as shown in the diagram below. Simply follow the wire from the sensor to the connector.

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kdauwg said:

The xj will stall intermittently at any speed idle to highway speeds althogh more often at speed. There is no warning no rough idle engine just loses power. This only occurs after the xj has been running for more then 10 or so minutes.The stall is very brief a second or less.

Click to expand...

I agree that your symptoms could very easily be the crank sensor. Follow Tim's comprehensive advice for troubleshooting it.

In the event that the light you see briefly on the dash is the "check engine light", pulling the stored codes from those events with a scan tool or a code reader may provide a code that relates to/confirms this.

Tim

Thanks this looks promising I will look at the Jeep this weekend. Sooner if time permits. I really appreciate the quick and through responses. Just stumbled across this forum, have been on others but this one seem to be better than the others I have been on.

Again thank for the tips and the details are greatly appreciated!!

The xj is a 1999 so used the below procedure to test.

• 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.

As it is an interment problem I have tested it several times over the last several days I tested at different engine temps between b & c the result was open each time. I tested again today and the reading was .675 I pulled and replaced with a new one drove for 30 minutes and it appears to be resolved.
I played with the old one a bit after removing and the reading is usually open but a slight tap or placing on a heat source and the reading will be between .675-1.25

Will keep my fingers crossed.

Sounds like you got it.

Good luck, and update us in a few days.

Tim_MN said:

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.

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

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.

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. Jeeps do not tolerate low voltage or poor grounds and the ECM/ECU may behave oddly until you remedy this.



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.

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.


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


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 displays correctly, replace the CPS.

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.

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. 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.


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.

TESTING PROCECURE for 1987 – 1990 4.0 L engines

Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 – 275 Ohms. . If the CPS is out of that range by much, replace it.

Test # 2 - You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.


The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector may be on the passenger side, not as shown in the diagram below. Simply follow the wire from the sensor to the connector.

.
.

.

Click to expand...

kdauwg said:

The xj is a 1999 so used the below procedure to test.

• 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.

As it is an interment problem I have tested it several times over the last several days I tested at different engine temps between b & c the result was open each time. I tested again today and the reading was .675 I pulled and replaced with a new one drove for 30 minutes and it appears to be resolved.
I played with the old one a bit after removing and the reading is usually open but a slight tap or placing on a heat source and the reading will be between .675-1.25

Will keep my fingers crossed.

Click to expand...

Is the testing procedure the same as 1999 XJs as for 2000 XJs?

Thanks

Yes.

Thank you.

My daughter's ' 99 had the same problem,exactly as discribed.
Thanks to this thread, I replaced the cps and the problem was fixed.
Thanks !

It's been a couple of month and about 2000 miles and still going strong. Thanks for the advice it saved my butt.

Could the crank sensor be the result of a failure/shut down while in motion?

Magus2727 said:

Could the crank sensor be the result of a failure/shut down while in motion?

Click to expand...

If you are asking if the CPS/CKP can kill the motor while the vehicle is moving--yes, absolutely.

Without the CPS/CKP crank sensor signal the ECU/PCM can't trigger the spark. Thermal failure is an early sign of a failing CPS/CKP. Thermal failure is when the engine will start fine, run for a time--a wide variance of time--and then suddenly quit running. After it sits for a while it will start and run again for another short time.

I can start mine up again with in seconds... only has happend twice on me and both times while moving, one taking a turn the other on the freeway. both times it started right up when I realized...

two events are isolated by about 3 weeks...

Is there a consensus on these CPS sensors?

Hmmm.... Seems like it might be a good idea to carry a spare in my '99?

Are there different brands of them or are they only available at the dealer? Are there brands to avoid?

How much are they?

Thanks

The crank position sensor will do exactly what the original poster described. Carry a spare and only get them from the dealer.

When mine failed the sudden drop in RPM's from it stalling at speed was enough to blow out the pinion bearing in the rear of my 2000 Cherokee.
don't fool around with them, fix ASAP

Hi, I have a 1996 XJ (Jtec controller OBD II) with the same exact issue, but it also throws me a P2300 DTC or code 54 (with the ignition key cycle mode) "No Cam signal at PCM". I already replaced the CKP (Crank sensor) with a brand new MOPAR one and the CMP as well. The Jeep can run just fine for days with no symptoms at all but bam! it could suddenly stall or prediodically lose its power. CEL will became ON again.

The Jeep starts fine, fuel pressure is above 40 PSI, no pressure drop after shutdown, Did the wires wiggle test too and cleaned up all connectors.

I am seriously suspecting of a bad PCM, any thoughts?

Any help will really be appreciated. Thanks!

Just for giggles, go jiggle the wires that attach to the PCM at the 60-pin connector. Frank Z had a long saga going, and that is where he found his problem.