Starting a thread to discuss/investigate some intermittent engine stumbling/staggering issues I've noticed after I bought this TJ with regards to possible compatibility issues with having a PCM from a TJ with an Automatic
As per @RMETeeJay 's suggestion I've started a new thread here to post what my current issues/symptoms are and later what my findings will be when I start looking at wiring and any other possibilities such as bad sensors or grounds.
Here's what I've noticed so far along with the conditions under which they've happened:
High idle - When the jeep is running and not in gear, if the jeep rolls forwards (or even backwards) over a certain speed my RPM's will jump from the normal 750-ish to around 1100 rpm. Once I stop rolling, and after about 2-3 seconds, the RPM's will drop back down to about 750RPM again. The only other movement related action the jeep does is activate the daytime running lights once I start moving after starting the vehicle. These two events also happen almost simultaneously.
Hard stumbling/stuttering at low RPM - I've had a couple instances where I've driven up a steep section of trail or steep rough section of logging road that required using 1st gear and have had the engine bog down from lack of torque. During this relatively quick decrease in RPM the engine will start to misfire and stall. This starts happening around 600-650 RPM. I plan on re-gearing axles to eliminate this issue altogether in the future so that I'm not forced to use 4LO
Stutter/misfire with too much throttle input - We've all been there, you're in an underpowered vehicle driving up a hill and you have your foot to the floor hoping to coax a couple more miles per hour out of your rig... Except for my TJ apparently. Too much throttle input causes stuttering.
Hitting potholes to hard/fast - It happens to the best of us from time to time. This one will most likely make all the skilled and knowledgeable folk on here (not me) think that I definitely have a wiring issue. Whether it's a bad ground that rattled loose, a short in the harness where it might be rubbing against the valve cover, or a poor connection to a sensor such as the IAC. These are ALL valid points and I will be checking them at a later date when home from shift.
The last thing worth mentioning is the constant check engine light. I was told by the PO who installed the PCM that it is "due to the PCM being from an automatic and not having a sensor from an automatic trans hooked up"
I also have no idea what year of jeep this PCM came out of.
I will add info on my findings when I get home. In the meantime, any and all information is greatly appreciated. The more people I can get to help get to the bottom of this the better. On top of that, if anyone knows if a re-flash or programming is needed when buying a PCM designated for a manual trans that would be sweet.
As per @RMETeeJay 's suggestion I've started a new thread here to post what my current issues/symptoms are and later what my findings will be when I start looking at wiring and any other possibilities such as bad sensors or grounds.
Here's what I've noticed so far along with the conditions under which they've happened:
High idle - When the jeep is running and not in gear, if the jeep rolls forwards (or even backwards) over a certain speed my RPM's will jump from the normal 750-ish to around 1100 rpm. Once I stop rolling, and after about 2-3 seconds, the RPM's will drop back down to about 750RPM again. The only other movement related action the jeep does is activate the daytime running lights once I start moving after starting the vehicle. These two events also happen almost simultaneously.
Hard stumbling/stuttering at low RPM - I've had a couple instances where I've driven up a steep section of trail or steep rough section of logging road that required using 1st gear and have had the engine bog down from lack of torque. During this relatively quick decrease in RPM the engine will start to misfire and stall. This starts happening around 600-650 RPM. I plan on re-gearing axles to eliminate this issue altogether in the future so that I'm not forced to use 4LO
Stutter/misfire with too much throttle input - We've all been there, you're in an underpowered vehicle driving up a hill and you have your foot to the floor hoping to coax a couple more miles per hour out of your rig... Except for my TJ apparently. Too much throttle input causes stuttering.
Hitting potholes to hard/fast - It happens to the best of us from time to time. This one will most likely make all the skilled and knowledgeable folk on here (not me) think that I definitely have a wiring issue. Whether it's a bad ground that rattled loose, a short in the harness where it might be rubbing against the valve cover, or a poor connection to a sensor such as the IAC. These are ALL valid points and I will be checking them at a later date when home from shift.
The last thing worth mentioning is the constant check engine light. I was told by the PO who installed the PCM that it is "due to the PCM being from an automatic and not having a sensor from an automatic trans hooked up"
I also have no idea what year of jeep this PCM came out of.
I will add info on my findings when I get home. In the meantime, any and all information is greatly appreciated. The more people I can get to help get to the bottom of this the better. On top of that, if anyone knows if a re-flash or programming is needed when buying a PCM designated for a manual trans that would be sweet.
