I stumped all the mechanics near me HELP

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FatherGrim

New member
Hey guys i got a 2000 jeep cherokee sport. 4.0 6cyl 4x4, has like 267k miles.. been having some problems trying to find the problem. jeep was running fine then all of a sudden it would die in gear, got it to idle perfect runs like a top no misfires nothing but the moment you put it in drive it loses its mine. Started with a crankshaft positioning sensor, replaced that then camshaft sensor, replaced that. hooked it up to my buddies snap on code reader and the codes are all over the place Ingnition coil 1-3 show up while in gear, when idle the only code that shows up is Generator field something cant remember the full code. the thing that is stumping my buddy is that the codes show up and then go away then come back and then get diffrerent codes. Is my computer shot because of the crazy randomness of the codes, replaced everything that the code reader spit out at us but the codes still show up, even replaced the throttle body... id love to get my rusty but trusty jeep back on the road but i have no idea why its running this way.
 
JPNinPA said:
Check battery voltage and connections. A bad power and or ground will cause phantom codes.


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Jeep was in a bad front end crash, fixed everything and changed to a GM one wire alt, so i was thinking this also but the problem is i drove this for roughly 6 months or more after i got it repaired with that alternator, it kinda felt at first when i notice the symptoms it was like the fuel pump just up and died.
 
A Crank position sensor failing can leave you high and dry. But you mention you changed that.

Unless you used aftermarket CKP that have been known to be bad out of the box.

Also the the power snd ground i mention is the wires and connection points not the sources. With a bad ground voltages can vary, drooping below required thresholds. That is why you might see the codes changing.

However both of your codes revolve around spark and power, you can get the alt checked.


Providing the actual code #s allows for more direct things to suggest and limit responses on non-issues.

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so the alt is new, the whole front end is new also, i do know that i had to put a quick disconnect into the jeep. but you are saying check and make sure that the wires to my ignition coil for instance is getting a proper ground, aka the plug that goes into the coil. bc we replaced the ignition coil pack and spark plugs.
 
Battery to chassis ground.
Battery to engine ground.
Power to starter, pcm and fuse box..... if the wires are corroded or the connections oxidized the voltage drops and limits current. Because of this the PCM gets wrong signals from sensors causing odd CEL codes.



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thanks going to try and get over to the shop at some point to test all these, i think because we have redone the ground from battery to chassis and engine, with the new front end he doesnt believe anything like that could be bad, ill have to check the ground from the PCM(assuming this is the "computer) if it has one, that being said my buddy has kinda given up on the idea its anything other then a potential bad computer.
 

Got some more info, replaced the ignition coil, remade the ground from the computer to the frame, replaced the fuel rail, replaced the temp sensor. my jeep has a GM one Wire alt so i believe the code p0622 is because i dont have the volt meter hooked up to it, this thing runs perfect at idle but the moment i put it into gear i misses and chuggs. the only thing i havent replaced now is the computer and the wiring harness, im back to square one.

The codes i get now are still

P1391
P0361
P0362
P0363
P0622
 
The P1391 - Intermittent Loss of CMP or CKP- Loss of the Cam Position Sensor or Crank Position sensor has occurred.
Being you changed these, they are not likely the issue. FYI many aftermarket sensors are often bad out of the box or fail quickly. Esp the CKP. Also check that the ODPA is clocked properly to the timing.

P0622 - Generator Field F Terminal Control Circuit -An open or shorted condition detected in the generator field control circuit.
This may be due to the F connector not being used on the single wire. Or the PCM has an internal issue.
Is your alternators internal regulator overcharging? Though it is new, things fail.

The P0361, 362 and 363 are not typical for the TJ and not listed in std codes. 351 maybe but these 4.0s use 3 coil packs shared between 2cylinders each. At a minimum check if there are vac leaks at each cylinder.

What rpm do you idle at?

My thoughts are the alt not using all the connections is causing an issue. But why now? Idk have you done a hard reset of the PCM lately?


Regards,
JPNinPA

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Last edited:
at idle it runs at around 900-1000 im not really sure, it was in a front end accident and the wiring to my headlights and headlight switch pretty much got fried and or broke will this have any effect to anything?
 

Idle should be 750 rpm. When it first starts cold it may hold 1000 fir 30 sec or so but should idle at 750. You have a vacuum leak. That may be your issue when you put it in gear.

Those codes are odd.

Clean the TB and IAC. If it still idles above 750 take WD 40 or TB cleaner and spray around the intake starting at the TB base. Then spray each injector base, each spark plug and then vac lines.


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Last edited:

IMG_0689.JPG

Front end collision? Did you go this far with the vac checking?


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yeah, actually that vacuum reservoir for a long time we had unplugged and ran fine, but then we found out that we needed it to change where the heat was coming from
 
Ok looked into one wire issues.

Monitor battery voltage using a DMM.
12.6v engine off?
Start vehicle 14.4v?
Turn on lights, heater fan, ac on high. Radio... measure voltage. What do you read?

Have someone hold the brake and put it in gear. Measure voltage.
What do you read?

Are the readings constant or fluctuating a bit?


Stock alt is 117 A. One wires are typ 90-100A

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Last edited:

yeah so my friend replaced all my vac lines, i had a leak in one but taped it up months ago, he replaced a bunch of gaskets still having the same problem. yeah so i bought a one wire that was like 90 amp but then i upgraded to a new one that says 140 amp, im going to replace that tho with one that my friend has on a parts jeep so ill have the correct everything. im at a lost and he is as well...he keeps telling me its shot.
 
So can you provide the voltage readings or not? It doesn't cost anything if you have a DMM


Regards,
JPNinPA

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So it didn’t drop when put in gear with everything on lights radio fan on high AC or defrost?

And it still sputtered and missed?

Well then its not likely the alternator.


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