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Unplugged the MLPS and jumped at the starter solenoid. No change. It still misses on 4 (?) cylinders if you put it in reverse and stomp on it. If you baby it it backs up just fine, no missing. You can then put it in forward gear(s) and drive all day long, no problem. We swapped a borrowed trans solenoid pack but that didn't make any difference either. This truck is being put up for sale. He is so aggravated at it he went yesterday and bought a Dodge!
Could it be something with a vacuum line somewhere or an engine electrical issue like a wire just trying to ground out when the engine torques in the direction of reverse?
Originally Posted by eakermeld
It still misses on 4 (?) cylinders if you put it in reverse and stomp on it. If you baby it it backs up just fine, no missing. You can then put it in forward gear(s) and drive all day long, no problem.
Well, subject is a batch fire system, (I think), and putting both comments in context, is it possible that somehow you are losing 1 bank of injectors when backing up? Might require rigging up some remote noid lights?
Yes, you are correct. it is dropping 1/2 the cylinders. The O/D light is flashing when this happens, so that means it is going into "limp home mode". Both me and my friend have spent HOURS examining wires of all kinds looking for rubs, breaks, frays, or missing/malfunctioning grounds and have yet to find anything wrong. Everything looks like new under there! If I knew what was sending the signal, or IF a signal is even being sent, I might be able to trace a single wire and find it, or bypass the bad wire and fix the problem.
If it starts misfiring only in reverse, even with the MLPS disconnected, I can tell you it's almost certainly not a transmission problem.
It's almost guaranteed to be either be a ground problem, or a bad connection in engine harness when the drivetrain torques over in the opposite direction.
The check the fluid level was a very good idea but for that reason, it dropping half the cylinders I've from the start thought it was an electrical issue.
My experience with low fluid refilling after a complete drain trans and converter for a fluid change, if low and low enough the engine stalls. It comes to a sudden and complete stop no chance to misfire. If there is an in between? I've never hit on it.
I realize what has been done but still to a degree yet suspect a computer problem.
It the computer itself or it something screwing with it or some combination of both of em.
As pointed out by notenoughtrucks the key to it is first finding out which circuit/s then figure out the why.
A noid light or two would verify that it is dropping a batch in short order or if it just "seems" like it is doing that, a good idea and would be a great next step.
I do understand what has been done and the time spent on it, gave up on it a little to soon IMO.
I also understand I don't know his situation and don't need to know it, he had to do what he had to or simply wanted to do about the problem, not a thing wrong with that in anyone's book.
Run a temporary ground wire right from the battery negative to the engine block somewhere. Just grab a bolt and put the wire under it. Next, with the engine running, start wigging the main loomed harness going to the engine. Move it around a lot if you have to.
Try completely isolating the transmission - disconnect both the solenoid pack and MLPS. The transmission will still shift into reverse. If the problem still happens, you can pretty much rule out it having anything to do with the transmission.
You could also potentially rule out reverse torque by disconnecting the shift cable down at the transmission. If it acts up when you move the snifter into reverse doing that, it's probably something in the shift linkage under the dash mashing into some wires.
Run a temporary ground wire right from the battery negative to the engine block somewhere. Just grab a bolt and put the wire under it. Next, with the engine running, start wigging the main loomed harness going to the engine. Move it around a lot if you have to.
The battery is already grounded to the engine and the frame. We even ran jumpers to the body grounds and one direct to the trans.
Try completely isolating the transmission - disconnect both the solenoid pack and MLPS. The transmission will still shift into reverse. If the problem still happens, you can pretty much rule out it having anything to do with the transmission.
We tried unplugging both but then it goes into limp mode as soon as you move the shifter, no matter what gear is selected.
You could also potentially rule out reverse torque by disconnecting the shift cable down at the transmission. If it acts up when you move the snifter into reverse doing that, it's probably something in the shift linkage under the dash mashing into some wires.
Run a temporary ground wire right from the battery negative to the engine block somewhere. Just grab a bolt and put the wire under it. Next, with the engine running, start wigging the main loomed harness going to the engine. Move it around a lot if you have to.
The battery is already grounded to both the block and the frame, nice and clean. We even ran jumpers to the body grounds and direct to the trans case.
Try completely isolating the transmission - disconnect both the solenoid pack and MLPS. The transmission will still shift into reverse. If the problem still happens, you can pretty much rule out it having anything to do with the transmission.
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When we did this, it went instantly into limp mode as soon as you moved the shifter, no matter which gear was selected.
You could also potentially rule out reverse torque by disconnecting the shift cable down at the transmission. If it acts up when you move the snifter into reverse doing that, it's probably something in the shift linkage under the dash mashing into some wires.
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