01' XJ severe engine jerking with RPM spiking

2001 4.0 126k miles. Starts and runs smooth for a while, then at operating temp randomly vigorously jerks with visible RPM spiking while driving at any speed. RPM gauge will spike very quickly and high. Will also sometimes bog down/sputter and die at idle. The jerking is very bad and strong, causing the whole vehicle to buck and make me cringe. (initially only did this in hot climates/low elevations and pulled no codes, but now does it everywhere and more often)

Will cracked headers cause this or is it something less simple? It used to do this jerking with no codes for a while, but then over time produced codes as it got more frequent.

Current codes after ECU reset and exhaust leak fix:
1. P0353 ignition coil B primary/secondary circuit
2. P0352 ignition coil C primary/secondary circuit
3. P1391 interm loss of CMP or CKP

Prior codes before fixing an exhaust flange leak (post pre-cats) and before ECU reset:
1. multiple cylinder misfire
2. P0456 evaporate emissions small leak detected
3. cylinder 5 misfire

Possible culprits?
1. cracked exhaust manifold - can produce many symptoms, but I've never heard of this specific jerking. Mine has an audible leak but I still can't pinpoint the location.
2. coil pack - the plugs are getting an orange spark, but not a "blue spark" as some say. all 6 are firing though. The springs inside the boots for position 6 and 3 are a little bent/stretched. I tested the coil pack cold (~50 degrees ambient). All three coil primary windings read 1.8 ohms on an analog multimeter and 2.0 ohms on a digital multimeter (both multimeters read 1.2 ohms resistance when grounded/tested) I did not get any readings on the secondary windings because supposedly this new coil design has a diode in it.
3. recently replaced NGK v-power (3459) plugs - haven't heard anything bad about them
4. camshaft position sensor - replace or reindex? (distributorless engine, the CMP sits on top of the oil pump drive)
5. oil pump drive
6. o2 sensors - one of the downstream o2 sensors on the pre-cat is saturated in coolant from a small leak, but is not permeating the seal
7. bad ECU/PCM

I cleaned the IAC, TPS, MAP connections and throttle body. Replaced CKP (aka CPS) and TPS about 3 years ago- the CKP fixed the dying and no start issue. Spark plugs look good. Recently sealed an exhaust leak at the flange connecting the pre-cat to the midpipe. Now runs much quieter and a little smoother, but still has the same jerking symptoms. Replaced engine and tranny mounts in preparation for the new exhaust manifolds, but I would rather fix this jerking problem first because it might buck strong enough to crack new headers.

Any thoughts or ideas would be greatly appreciated!

Symptoms sound like a vacuum leak on the supply to the MAP, or a bad TPS, but this:

Current codes after ECU reset and exhaust leak fix:
1. P0353 ignition coil B primary/secondary circuit
2. P0352 ignition coil C primary/secondary circuit
3. P1391 interm loss of CMP or CKP

Suggests a bad crank sensor or wiring issue to me.

But I am not the expert here on 01s.

Did you ever solve this problem or learn any more about what did or did not cause it?

In a 2000-01, use Autolite APP-985 or basic Champion plugs. Make sure the plug boots are fully engaged on the plugs.


Solve the P1391 first, the other codes will likely not return. If solving the P1391 does not cure the symptoms, Look to the O2 sensors and the exhaust mainfold. Bucking, jerking and stalling (without a P1391) is almost always an O2 sensor issue.

P1391

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

Symptom:
P1391-INTERMITTENT LOSS OF CMP OR CKP

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


Potential Fixes:

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

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 service manual.

ill also confirm that P1391 interm loss of CMP or CKP will cause every misfire code in the book.

Hello everyone, I was hoping maybe this issue got resolved since I am currently experiencing the same thing, I have had the jeep for a year now with no issue, even went on a 1200 mile road trip with no issue at all!! The jeep has 243xxx miles on it currently and just the other day it started to stall/misfire while driving on the highway after the jeep was warmed up. Some times it will stumble bit at low speeds but with some throttle it clears right up. I have taken the Jeep to Uwharrie many times and a couple other fun parks and the jeep has always been the one vehicle we can count on so this issue now makes me nervous to go anywhere in fear it may not start. I checked the cps with a volt meter and it seems ok, I put some dielectric grease in the plug since it didn't look bad. I also did the same to the other sensors on the intake. i don't have a scanner so I'm not sure what the codes could be unfortunately but I was hoping for some other options. Thanks!

You need to get the codes read, but yours sounds like typical tps going bad.

What year is it? Sounds electrical, which could be any one of a whole laundry list of things.



Or fuel injectors/fuel related. Depends a lot on what year it is. I anot going to assume it is 2001. Or even mecahical like a bad Distributor I had on an 87.



Year?

youtubemech said:

Hello everyone, I was hoping maybe this issue got resolved since I am currently experiencing the same thing, I have had the jeep for a year now with no issue, even went on a 1200 mile road trip with no issue at all!! The jeep has 243xxx miles on it currently and just the other day it started to stall/misfire while driving on the highway after the jeep was warmed up. Some times it will stumble bit at low speeds but with some throttle it clears right up. I have taken the Jeep to Uwharrie many times and a couple other fun parks and the jeep has always been the one vehicle we can count on so this issue now makes me nervous to go anywhere in fear it may not start. I checked the cps with a volt meter and it seems ok, I put some dielectric grease in the plug since it didn't look bad. I also did the same to the other sensors on the intake. i don't have a scanner so I'm not sure what the codes could be unfortunately but I was hoping for some other options. Thanks!

Click to expand...

If the Check Engine Light is ON, your Jeep is trying to tell you what is wrong. Scan for any active or pending trouble codes.

If the Check Engine Light is not ON, it is likely one or more of the engine computer sensors has a bad connection, bad wiring, or is faulty. Visual inspection of the sensor wire plugs and wire harnesses, and some basic wire continuity testing and sensor testing with a $6-15 volts/ohms multimeter is where you should start your troubleshooting and diagnostics.

The Jeep is a 1999, Ill take it to the store to get the codes read, I've just been nervous to take it anywhere after this issue in fear ill have to tow it home

You can buy a cheap OBD-II trouble code reader for about $25. I carry one all the time in both of my XJ's.