allevolution

2000 Cherokee 175k Been fighting this for almost a year.
Let me give a short summary of my issue.
-It is an intermittent spark issue
-Fuel pressure is where it should be
-Compression is 150-155 cold

EDC codes that are reoccurring
P1391- intermittent loss of cam/crank
P0340- cam circuit malfunction
(havent seen this one in a while and I think I resolved this with the PCM connector I recently replaced)

P0351- ignition coil a malfunction
P0352- ignition coil b malfunction
P0353- ignition coil c malfunction
P0132- sensor 1 high voltage
(rear O2 is out, this may be to issue with heater circuit)


-90% of the time Hard starts, will have to cycle the key 2-5 times. Sometimes it will start first turn of the key. Doesnt matter is the motor is hot, or cold.

-Once is it started, 50/50 chance it will run like pure **** (misfiring) and have to be turned off then restarted again.
(still has hard start if turned off either way)

-If it does start without an issue, idle will be normal but it will still have a problem when I apply load to the motor. Accelerating up to highway speed (40-50mph) it will struggle.
UNLESS I floor the pedal WOT, the motor will accelerate quickly and the misfire issue will rarely show up again.
(further into this I will have to floor the car several times then the misfire will disappear)

-VERY rarely will it have an issue with misfiring after running for sometime.
(Issue happens mostly only at startups)
If this rare situation does occur, it will misfire at complete random.

I think I have the major bullet points there.
With all that being said if we have a warm day (Chicagoland weather)
Seems like initial start up is alot easier.
Would an IAT have any affect on anything?

But onward with the long list of parts:
-Cam synchronizer/ oil pump drive DEALER part
(and calibrated 110% accurately using snap-on scanner)

-Cam sensor NAPA part (swapped with dealer part with no difference)

-Crank sensor DEALER part (swapped yesterday with another new dealer part and no difference)

-PCM from autocomputerexchange (out of Flordia reputable place)

-PCM Black connector (connector was a little jiggly and had seen better days, now its tight and every pin is making full contact)

-All wiring from Cam sensor to PCM reads fine with meter.
Same with Crank sensor wiring.
All connectors are tight, no wiggle room and pins in both connectors are tight.

-Fuel injectors where cleaned with new o rings
-New TPS

I am really at a loss here please someone, anyone help me out with an idea!

Videos that show everything that is wrong.
Please please please watch all of these videos it will really give you a perspective of whats going on with the car and when it attempts to start, or is running and starts to have random misses.

CCKen

It may be a voltage drop between the ASD relay and the Ignition Coil Rail.

Do you have an Ignition Coil Capacitor? See pic. On the right side of the engine.

The capacitor is wired in parallel with the power wire from the ASD relay to the Rail. If you have one, disconnect it and see what happens.

allevolution

I tried disconnecting that capacitor and there was no difference.
But I will leave it disconnected and see if there is any change. Thanks for that info!
I wonder why there would be a capacitor there to begin with?

Add to those parts
-Coolant temp sensor (sometimes people say this can cause a rough start, or rough running at startup)
-Missing the NSS (bypassed to start right now)
so I am about to install a new NAPA one right now.

allevolution

Im starting to guess that whatever advances the spark is causing all these issues.
Because majority of the time its only when the rpm is increased under load.

How is the spark advanced? Or what controls spark advancing?
And would WOT have a default setting that would explain all of this?

CCKen

The Crankshaft Position Sensor controls spark advance.

WOT data comes from the TPS.

The Camshaft Position Sensor is involved in fuel injector sequencing (pulse width - rich/lean) inconjuction with the Crank Sensor, but the number one contributor to rich/lean is the MAP Sensor. It's involved from the very begining of the start sequence all the way through the entire running open/closed loop regime.

During acceleration under load, the PCM is in Open Loop where the O2S inputs are ignored and inputs from all the other engine management sensors are compared to presets in the PCM. If, during this time, signals from a defective sensor will/can cause engine stumble due to ignition timing, a rich condition, or a lean condition (Fuel, Air, Ignition).

Your DTC codes would indicate an ignition problem and a fuel sequencing problem.

freegdr

write down codes ,clear them restart see which ones come back first thing Id do.

allevolution

Thats all great information, and I think this next link makes sense of it. (assuming this link is credible)

http://jeep.blackonyx.net/pdfs/jcss.pdf
"Cherokee PCM will kill injectors on misfiring cylinders in an attempt to preserve the catalyst and leave them offline until the engine is restarted."

So that would explain the worsening of the stumble, when one is present.
And continuing on with that article. I am going to see if adjusting my cam synchro (taking a guess as to the adjustment) since the stretch on the timing chain isnt really measurable. Didnt think it would be enough to cause all these issues.
But again I am pretty much guessing here.

allevolution

Today the two codes that came back after the third startup of the day
were:

p1391
p0138

I still have the capacitor unplugged by the oil filter housing as suggested by CCKen.
And cant believe it (probably the warmer weather)
But the car didnt stumble on itself but only once.

Im thinking the PCM being reset had alot to do with that also.

freegdr

0138 is oxygen sensor shorted wonder if that could be causing a issue here causing the other

CCKen

Ref. P0138.

Often, careless owners will not secure the downstream O2S harness out of the way of the drive shaft and it will get tangled up in it...shorting out the O2S wires.

There have been cases where a shorted O2S will fry a PCM; then again, some have had luck just repairing the wiring and moving on.

Assuming you have a Federal emssions exhaust system with one downstream O2S, perhaps you should check the after CAT O2S wiring.

Ref. P1391.

Examine the wiring harnesses in the engine bay for chafing down to bare wires. Especially around the end of the fuel injector wiring manifold and the end of the cylinder head cover. There have been cases where the wiring in this area have chafed through the loom and into the wiring. The Crank Sensor wiring goes through this area, and so does the Cam Sensor wiring, on their way to the PCM.

allevolution

Jeep is forsale, dont have the time to put into figuring this misfire out anymore.
Its my only car and I cant risk loosing my job (This would be job #2) because of it.

Check it out the NEW parts list is through the roof. All receipts included.
Someone will get a good deal on a bunch of new quality parts alone.

https://www.cherokeeforum.com/f70/ch...9/#post2699631