My 94 GC 4.0L has a new coil, cap, rotor, plugs, wires for a stalling problem. It was towed to dealer and they called the coil bad. It started for them and then shutoff after running for a while. I paid there check-out cost and installed my own parts. It still seems to display stalling tendencies. It misses and stumbles and feels as if it will die completely again. I feel the problem might be with the coil pickup, or the crank sensor, or maybe the PCM. With the engine running properly is there anyway to test and narrow the options?
Intermit Ignition Failure
- Thread starter Nomad
- Start date
SteelHeadz
Super Moderator
Any DTC's? . A stumble, misfire and or a low idle could be on the fuel system or electrical. There are multiple possibilities on what could cause these symptoms such as the IAC, map sensor, TPS, fuel pump, etc.
54cj3b
New member
welcome to the jeep world of ownership 
JeepsEatEveryPennySucker (is the sloagan)
There known for all kinds of electrical gremlins
and steelhead just gave you the most likly culprits of your issues ,
I love spending money so I own 6 jeeps lol
get used to it being broke that is :shades:
happy jeeping
JeepsEatEveryPennySucker (is the sloagan)
There known for all kinds of electrical gremlins
and steelhead just gave you the most likly culprits of your issues ,
I love spending money so I own 6 jeeps lol
get used to it being broke that is :shades:
happy jeeping
SteelHeadz
Super Moderator
Take it to a local parts store like Autozone etc. and they will scan your vehicle for free.
I have had the same problem for a long while now, and have changed many parts like you and still nothing..
another symptom that mine has is that it shuts off if i live it idling this happens when cold or after its been off for about 10 minutes,
I went and timed how long it takes it to shutoff and it has always been around 15 minutes..
any ideas on that one?
another symptom that mine has is that it shuts off if i live it idling this happens when cold or after its been off for about 10 minutes,
I went and timed how long it takes it to shutoff and it has always been around 15 minutes..
any ideas on that one?
MudderChuck
New member
I've had the same thing happen for any number of reasons. Had the IAC stick either hot or cold. I just spray some penetrating oil down the "in" side orifice for the IAC and repeat a few times while the motor is running (word to the wise, make sure the spray tube is on the spray oil nozzle securely, I almost lost one down the TB). Blip the throttle a few times ti get the IAC piston moving. I now repeat the process at least a couple times a year and avoid problems before they happen.
Bad battery was sucking down the voltage a little, which also made the IAC sluggish.
Had a partial short on the CPS which sucked down the 5 volt reference (in) voltage for any number of sensors. The 5 volt supply seems to be interrelated someway, either because the drivers (in the PCM) are the same or maybe the drivers are wired in pralell. Could be any sensor from the rear O2 sensor to the sync sensor, sucking down the 5 volt circuit.
My anti theft module was failing, remote door locks worked iffy, it also affected the ASD circuit. Motor ran like a failing CPS (barely ran).
Had a bad splice in the ASD circuit, which I found by luck (and rather quickly) by shaking a harness up by the drivers side heater vent. Which was also part of my remote door opener circuit harness. Wish I would have found the bad splice (connector), before I bought a new module.
I usually begin now by cleaning connectors, before I buy sensors or modules. Way too often the problem lies in poor conductivity (corroded or loose connector pin or splice) and not at the sensor. And/or a wire is cooking on the exhaust someplace (rear O2 sensor, CPS, front harness where it goes down the front of the motor etc.)
Bad battery was sucking down the voltage a little, which also made the IAC sluggish.
Had a partial short on the CPS which sucked down the 5 volt reference (in) voltage for any number of sensors. The 5 volt supply seems to be interrelated someway, either because the drivers (in the PCM) are the same or maybe the drivers are wired in pralell. Could be any sensor from the rear O2 sensor to the sync sensor, sucking down the 5 volt circuit.
My anti theft module was failing, remote door locks worked iffy, it also affected the ASD circuit. Motor ran like a failing CPS (barely ran).
Had a bad splice in the ASD circuit, which I found by luck (and rather quickly) by shaking a harness up by the drivers side heater vent. Which was also part of my remote door opener circuit harness. Wish I would have found the bad splice (connector), before I bought a new module.
I usually begin now by cleaning connectors, before I buy sensors or modules. Way too often the problem lies in poor conductivity (corroded or loose connector pin or splice) and not at the sensor. And/or a wire is cooking on the exhaust someplace (rear O2 sensor, CPS, front harness where it goes down the front of the motor etc.)
please add in corrosion at ground and connections use of never seize [nickel type] and nonox also lamp grease ......
I have a new job so time to figure it out has been limited. New crank sensor seemed to have little affect. The 55 code is the only one I have ever found, which I think is a system normal code. During one attempt to diagnois the engine shut off 4 times after running 10-20 minutes, it would restart with no problem. After the 4th time it ran for 45 minutes with no more issues. During this last weekend it shut off after about 5 minutes and would not restart. The ground cable / stud has been checked and cleaned, no codes, no spark. It currently has new plugs, wires, cap, rotor, coil, CPS. I am wondering if the PCM is the culprit. Is there any way to test this theory? I appreciate all the help.
SteelHeadz
Super Moderator
Try swapping the ASD relay for a known good relay and see if it shuts off.
MudderChuck
New member
Pretty sure the cam position sensor and the CPS share a driver in the PCM. If something is shorting or making a poor contact. the 5 volt index voltage to the CPS and the cam position sensor may be low.
I'd check the cam position sensor voltage.
Then like SteelHeadz recommended, the ASD circuit. The ASD circuit in my XJ went through the remote door unlock (black box) and was part of the anti theft system. It started acting up and turned out to be an iffy contact in a splice. ASD supplies battery voltage to the ignition coil and the alternator field windings, among other things. The pulse from the CPS allows the PCM to close the ASD relay, the primary voltage to and through, the relay is also a factor. Low input or output voltage to (or through) the ASD primary and an iffy CPS can cause almost identical symptoms. Motor misses, has low power, stalls and barley runs, starting can also get real iffy. You should get very near battery voltage testing the coil input wire. Not sure of the wire color on the GC, likely dark green with a stripe.
I'd check the cam position sensor voltage.
Then like SteelHeadz recommended, the ASD circuit. The ASD circuit in my XJ went through the remote door unlock (black box) and was part of the anti theft system. It started acting up and turned out to be an iffy contact in a splice. ASD supplies battery voltage to the ignition coil and the alternator field windings, among other things. The pulse from the CPS allows the PCM to close the ASD relay, the primary voltage to and through, the relay is also a factor. Low input or output voltage to (or through) the ASD primary and an iffy CPS can cause almost identical symptoms. Motor misses, has low power, stalls and barley runs, starting can also get real iffy. You should get very near battery voltage testing the coil input wire. Not sure of the wire color on the GC, likely dark green with a stripe.
MudderChuck
New member
Without an open signal from the door opener (key fob), my security module deactivates the ASD relay or interrupts the ASD circuit. There are more than a few types of security modules out there (even OEM).
sorry about hunting demons...the way i will do this watch the tech is it falls fast its ignition, if slow its fuel -this is rule of thumb ! 2 systems are at work here next is a pain to do set a vac hose and ''t' to the manifold from inside so you shoot some carb cleaner in the hose when it dies if it fuel it will try to run on >>>also relays do get weak if they are 4/5 pole Bosch type used replace with sealed 30 amp 5 pole lamp one costing app.8.00 bucks -look at terminals for breakages /melted blocks ---if it has this one at the mag pick in distributor---sorry if is broken rant just trying to help ideas ....i write down what i do know and what works with what and how ....this is a pain but works for me for years on working on autos -shotgun repairs are too damn costly so please read and learn how things work together ..... the it sounds like something is getting hot and breaking up
SteelHeadz
Super Moderator
There should be 1 just below the exhaust manifold flange. The DTC's will not extinguish or reset if it's currently active.
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