RangerRyan

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 cant 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
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 would rather fix this jerking problem first.

Any thoughts or ideas would be greatly appreciated!

Jeepin'_Aint_EZ

Seems to me that the coil pack is the culprit. Once it heats up, resistance increases and the coil pack fails. Who can chime in what the resistance should be through one of these? I'd test it when its cold, then test it right after it starts getting fussy

RangerRyan

Bump - does anyone know how to properly test this coil pack or have any other suggestions?

RangerRyan

I tested the coil pack cold (~50 degrees ambient) using this chart below. 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.

On a side note- the springs inside the boots for cylinders 6 and 3 are a bit bent and stretched. The rest are perfectly stiff and straight. The boots are still good and show no internal damage.