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The_97_Sport
November 5th, 2017, 19:31
:new:
I have been struggling with my 97 XJ sport 4.0L for a very long time now.
the problem does not seem to change no matter what i do.
Here's the symptoms:
1.when at idle it will seem as if its ok, but then it will bog down and jump right up again to normal and repeat, but it will not stall. sometimes, the idle will become very rough, then it will be nice and smooth and repeat; all of these symptoms are consistent and in no particular order.
2. when accelerating regardless of RPM, speed, or engine temp. it will sporadically bog down, hesitate, then all of the sudden accelerate at full power again. this symptom is also consistent.
3. check engine light is on with the following codes:
P1391: CKP or CMP Sensor Signal Intermittent
P0135: O2 (B1S1) Heater Circuit
P0141: O2 (B1S2) Heater Circuit

after scanning the OBDII it seemed straight forward so i replaced the cranksahft position sensor with a genuine MOPAR sensor from the dealer as well as the precat O2 sensor with a OEM NTK sensor. i did not replace the post cat O2 because i am making the assumption the allegedly bad precat O2
was giving the post cat O2 an incorrect reading.
anyway, after replacing these parts and clearing the computer, the same codes still came up and the problem still existed.

i did some further research online and found out it could be the PCM causing false codes so i opened up my PCM and found 2 broken pieces of a circuit floating around inside so IT HAD TO BE THE PROBLEM right?? WRONG.
replaced the PCM with a rebuilt and the problem still persist. and the exact same codes come up from the OBDII.
at this point im ready to give up and realized i never checked my MAP sensor so i started it up, unplugged the sensor and the jeep still ran, but it wouldnt rev past around 3k RPM, but my understanding is when the MAP sensor is unplugged it should not run at all so i replaced the MAP sensor and still no change; the problem still persists and the engine light is still on, but i have not had it re-scanned yet.

anyway, i am pretty burnt out and i'm afraid i may be missing something obvious.
any help and opinions for next steps would be greatly appreciated.
for now, my next steps:
1. scan the engine light again check to see if same codes come up after replacing the MAP sensor.

Alopanec
November 5th, 2017, 19:49
Have you checked tps and iac

Runnin'OnEmpty
November 5th, 2017, 21:20
Did you replace the CMP/CamPosition sensor? Since the code indicates an intermittant signal, I'd try that next. I've had trouble with those on two different Jeeps.

Heavyopp
November 5th, 2017, 22:07
Did you replace the CMP/CamPosition sensor? Since the code indicates an intermittant signal, I'd try that next. I've had trouble with those on two different Jeeps.


He shouldn't have a camshaft position sensor in a 97 -- should have a distributor and not the coil rail of the 2000+ cherokee


My suggestion to the OP -- Run a compression test -- rule out a stuck valve or bent pushrod -- my 2000 thru all sorts of codes that I couldn't explain, chased my tail around for awhile until I ran a compression test and found exhaust valve for #2 cylinder was stuck open -- that caused all the O2 sensor and TPS codes due to raw fuel just dumping into the exhaust

Compression test is simple to do, just need a tester and 20 minutes

Tim_MN
November 6th, 2017, 04:51
Since you have trouble codes that indicate the O2 heater circuit, you need to inspect the O2 fuses, inspect the O2 plugs for corrosion and pushed back connector pins, and inspect the O2 wire harness for damaged wires or chafed wire insulation.

P1691 can be caused by an incorrectly index distributor, distributor failure, or cam position sensor issues. The cam sensor is located inside the distributor

The_97_Sport
November 6th, 2017, 06:48
Since you have trouble codes that indicate the O2 heater circuit, you need to inspect the O2 fuses, inspect the O2 plugs for corrosion and pushed back connector pins, and inspect the O2 wire harness for damaged wires or chafed wire insulation.

P1691 can be caused by an incorrectly index distributor, distributor failure, or cam position sensor issues. The cam sensor is located inside the distributor

interesting i did not know there were o2 fuses.
is this in the engine bay fuse box?
i have replaced my distributor and indexed correctly as well as the distributor cam sensor. alos, i am not getting P1691 so i should be alright there.

The_97_Sport
November 6th, 2017, 06:49
Have you checked tps and iac

TPS is new and the iac i cleaned last summer, but there are no codes for the iac so no reason to replace...unless theres something im missing.

The_97_Sport
November 6th, 2017, 06:54
He shouldn't have a camshaft position sensor in a 97 -- should have a distributor and not the coil rail of the 2000+ cherokee


My suggestion to the OP -- Run a compression test -- rule out a stuck valve or bent pushrod -- my 2000 thru all sorts of codes that I couldn't explain, chased my tail around for awhile until I ran a compression test and found exhaust valve for #2 cylinder was stuck open -- that caused all the O2 sensor and TPS codes due to raw fuel just dumping into the exhaust

Compression test is simple to do, just need a tester and 20 minutes

good info. i will definitely check my o2 sensor fuses first and move to the compression test if theres no issue with them. what pressures ranges in each cylinder should i be looking for??

Heavyopp
November 6th, 2017, 08:27
really just looking for uniform pressure through all the cylinders -- I had around 150 in all but #2 which was 0

I'm sure someone else will answer with an ideal pressure range

RCP Phx
November 6th, 2017, 13:55
It sounds like you haven't tried a scanner that reads "live data" and you really should to see what's going on in real time! There are many out there for cheap now days and will pay for itself in diagnostics.

The_97_Sport
November 6th, 2017, 19:22
update from next steps:
Checked the o2 sensor fuse and yes it was blown in half.
replaced the fuse, reset the engine light, and there was no hesitation while accelerating, but at idle it bogs down and revved back up again to normal idle; only not as frequently and does not drop to as low of RPM's. the CEL came back on and threw P1391 CKP or CMP Sensor Signal Intermittent.
I really cannot believe it would be the sensor itself because i replaced it with a genuine mopar sensor from the dealership just like everyone says; i did this to prevent struggling with aftermarket sensors.
the fact that this code was the only code the computer is throwing is a good thing because it narrowed it down to one problem, but its very hard to believe.
questions:
1. what else would make the sensor signal intermittent?
2. why would the engine start without excessive cranking? it starts right away.
3. if grease or oil got on the crank sensor while installing, could this be the issue?
there is a good chance some grease or oil got on the sensor while installing.

Tim_MN
November 7th, 2017, 04:51
The cam and crank sensors should be free of grease, oil, and debris.

P1391 - Intermittent Loss of CMP or CKP Signal. Loss of the Cam Position Sensor or Crank Position sensor signal has occurred.

P1391 – Possible symptoms:
(1) random misfire/stumble/stalling, often over bumps or right turns and when going into reverse.
(2) shorted out the Fuel pump/ECU power wire.

Possible causes
- Faulty CamshaftPosition (CMP) Sensor
- Camshaft Position (CMP) Sensor harness is open or shorted
- Camshaft Position (CMP) Sensor circuit poor electrical connection.

Symptoms:

-CMP SENSOR OUT OF SYNC
-DAMAGED TONE WHEEL/FLEX PLATE (CRANKSHAFT)
-DAMAGED TONE WHEEL/PULSE RING (CAMSHAFT)
-IRREGULAR LAB SCOPE PATTERN OF CMP SIGNAL

INTERMITTENT CKP SIGNAL LOSS WHEN WIRING IS WIGGLED
-IRREGULAR LAB SCOPE PATTERN OF CKP SIGNAL
-WIRING HARNESS INTERMITTENT

INTERMITTENT CMP SIGNAL LOSS WHEN WIRING IS WIGGLED
-SENSOR CONNECTOR/WIRING
-CAMSHAFT POSITION SENSOR
-CKP SENSOR CONNECTOR/WIRING
-CRANKSHAFT POSITION SENSOR

Often replacing the sensor fixes this code, but not necessarily. Therefore it's important to check the following:

• Check that the wiring isn't routed too close to to sharp metal edges, or to hot exhaust parts.
• Visually inspect the wiring at the sensor for any burn marks, discoloration indicative of melting or chafing of insulation
• Visually inspect the cam sensor for damage
• Visually inspect the reluctor wheel inside the alternator. Make sure the magnet is firmly attached.
• If all checks out okay, then replace the sensor.

If you buy any OBD-II engine sensors, make sure to buy genuine Jeep sensors.

Potential Fixes:

Fix #1:
Inspect your wire harnesses for damaged wires, chafed insulation, or failed wire splices. Use a volts/ohms multi-meter to check the resistance of the ground wire circuits from each sensor. Replace corroded ground wires/connectors and clean ground wire connection points.

Fix #2:
Timing may off. Re-index the distributor/cam sensor per the FSM instructions, or replace faulty distributor/cam sensor pickup module.


Google Scan Tools, O-Scopes and Toothpicks, and read the article.

A mis-indexed distributor/cam sensor may exhibit surging, light bucking or intermittent engine misfiring. This will most likely occur when the vehicle is at operating temperature and under a light load at approximately 2,000 rpm. The proper indexing procedure must be used as outlined in the Jeep Service Manual.

The_97_Sport
November 7th, 2017, 07:37
The cam and crank sensors should be free of grease, oil, and debris.

P1391 - Intermittent Loss of CMP or CKP Signal. Loss of the Cam Position Sensor or Crank Position sensor signal has occurred.

P1391 Possible symptoms:
(1) random misfire/stumble/stalling, often over bumps or right turns and when going into reverse.
(2) shorted out the Fuel pump/ECU power wire.

Possible causes
- Faulty CamshaftPosition (CMP) Sensor
- Camshaft Position (CMP) Sensor harness is open or shorted
- Camshaft Position (CMP) Sensor circuit poor electrical connection.

Symptoms:

-CMP SENSOR OUT OF SYNC
-DAMAGED TONE WHEEL/FLEX PLATE (CRANKSHAFT)
-DAMAGED TONE WHEEL/PULSE RING (CAMSHAFT)
-IRREGULAR LAB SCOPE PATTERN OF CMP SIGNAL

INTERMITTENT CKP SIGNAL LOSS WHEN WIRING IS WIGGLED
-IRREGULAR LAB SCOPE PATTERN OF CKP SIGNAL
-WIRING HARNESS INTERMITTENT

INTERMITTENT CMP SIGNAL LOSS WHEN WIRING IS WIGGLED
-SENSOR CONNECTOR/WIRING
-CAMSHAFT POSITION SENSOR
-CKP SENSOR CONNECTOR/WIRING
-CRANKSHAFT POSITION SENSOR

Often replacing the sensor fixes this code, but not necessarily. Therefore it's important to check the following:

Check that the wiring isn't routed too close to to sharp metal edges, or to hot exhaust parts.
Visually inspect the wiring at the sensor for any burn marks, discoloration indicative of melting or chafing of insulation
Visually inspect the cam sensor for damage
Visually inspect the reluctor wheel inside the alternator. Make sure the magnet is firmly attached.
If all checks out okay, then replace the sensor.

If you buy any OBD-II engine sensors, make sure to buy genuine Jeep sensors.

Potential Fixes:

Fix #1:
Inspect your wire harnesses for damaged wires, chafed insulation, or failed wire splices. Use a volts/ohms multi-meter to check the resistance of the ground wire circuits from each sensor. Replace corroded ground wires/connectors and clean ground wire connection points.

Fix #2:
Timing may off. Re-index the distributor/cam sensor per the FSM instructions, or replace faulty distributor/cam sensor pickup module.


Google Scan Tools, O-Scopes and Toothpicks, and read the article.

A mis-indexed distributor/cam sensor may exhibit surging, light bucking or intermittent engine misfiring. This will most likely occur when the vehicle is at operating temperature and under a light load at approximately 2,000 rpm. The proper indexing procedure must be used as outlined in the Jeep Service Manual.

Excellent information; very appreciated.
all electrical has been thoroughly inspected and the distributor indexing has been done correctly.
the only items you listed i did not inspect is the alternator reluctor wheel.
to give you some history, i have no clue if the alternator has ever been replaced and my battery is definitely greater than 5 years old.
i'm considering replacing these maintenance fundamentals before moving forward with a further diagnosis.
Currently, i am experiencing some electrical gremlins with my blinkers; regardless of what blinker i turn on, they always turn the hazard lights on. also, when i am driving my voltage reading is slightly above 14V on the dash.
i confirmed the hazard light switch is off and on the dash it shows only 1 blinker is on at a time, but outside both sides are blinking.
is there a chance all my problems are due to an old battery and old alternator?

Heavyopp
November 7th, 2017, 09:00
is there a chance all my problems are due to an old battery and old alternator?

No - battery and alternator shouldn't cause what is happening with your turn signals

Sounds like to have some damaged wire somewhere making all the wiring connect -- gotta be somewhere where all the wires are close together allowing them to touch -- maybe going thru the firewall or in the steering column

The_97_Sport
November 7th, 2017, 09:46
ok i am going to check my alternator reluctor tonight and provide an update hopefully tonight.

RCP Phx
November 7th, 2017, 10:21
ok i am going to check my alternator reluctor tonight and provide an update hopefully tonight.

There's no such thing! What are you going to test?

Tim_MN
November 7th, 2017, 11:14
The dashboard gauge should read between 13.8/14.4 volts.

Issues with the turn signal multifunction switch on steering column are common. A new turn signal clicker relay is not expensive. Also make sure any trailer wiring was done correctly, and has not failed. Clean and snug the related ground connections.

Remove the battery and the alternator and have them Load Tested.

The_97_Sport
November 8th, 2017, 07:42
wasn't able to get to load testing the alternator last night, but possibly this afternoon. i was reading online that its possible for Autozone or advanced auto parts to test alternators while they are still in the vehicle; can anyone confirm this?

Tim_MN
November 8th, 2017, 11:15
.. possible for Autozone or advanced auto parts to test alternators while they are still in the vehicle; can anyone confirm this?

Yes it can be done that way, but that is also the least accurate test method, and most likely to pass a weak alternator or battery.

The_97_Sport
November 8th, 2017, 19:20
I checked the voltage at the battery during idle and the multimeter read 14.1 to 14.2V.
when the idle bogs down it drops to about 13.1ish, but then jumps right up to idle speed again and its back to 14.1/14.2. It seems the drop in voltage is most likely due to the idle's sudden drop, but heres my questions:
1. could this sudden RPM drop be due to the alternator?
2. would turning on all electrical such as rear defrost, A/C, radio and brights be similar to load testing?
3. Would a weak alternator cause an intermittent CMP or CKP code?
This weekend i am going to make sure all electrical connections are nice and tight and clean all of the grounds and completely test the alternator.