Do I need a new PCM?
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Laughing Gas
Joined: May 2015
Posts: 826
Likes: 21
From: Golden, CO
Do I need a new PCM?
I've got a 5.8 with factory PCM and harness in my '52 which has been running fine for over a year… lately, however, I'm having some issues (inconsistent): 
1) driving down the road under normal acceleration, will lift off throttle pedal in advance of an intersection and the engine speed will pulsate a few times (rev up, down, rev up, down, rev up, down) before settling at normal idle speed as I come to a stop.
2) more problematic -- a few times now when I lift off throttle, the RPMs will not drop down to idle at all, so if I don't shift (E4OD) into neutral as I approach intersection, the engine will stall when I come to stop. Sometimes I can blip the throttle to make it correct itself.
Thoughts? Insight? No code being thrown to CEL. Truck runs fine otherwise, so wondering if this PCM is going bad??
1) driving down the road under normal acceleration, will lift off throttle pedal in advance of an intersection and the engine speed will pulsate a few times (rev up, down, rev up, down, rev up, down) before settling at normal idle speed as I come to a stop.
2) more problematic -- a few times now when I lift off throttle, the RPMs will not drop down to idle at all, so if I don't shift (E4OD) into neutral as I approach intersection, the engine will stall when I come to stop. Sometimes I can blip the throttle to make it correct itself.
Thoughts? Insight? No code being thrown to CEL. Truck runs fine otherwise, so wondering if this PCM is going bad??
Logistics Pro
Joined: Aug 2014
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2) more problematic -- a few times now when I lift off throttle, the RPMs will not drop down to idle at all, so if I don't shift (E4OD) into neutral as I approach intersection, the engine will stall when I come to stop
I don't understand, the RPMs are high, and the engine will stall when you come to a stop?
Sounds like the torque converter is locked when it should be unlocked.
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Laughing Gas
Joined: May 2015
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Likes: 21
From: Golden, CO
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Logistics Pro
Joined: Aug 2014
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Yes, the Torque Converter lockup is controlled by the computer via a solenoid.
Have you checked the electrical connections on the trans, make sure they are clean and no corrosion.
Do you have a transmission cooler or a transmission temperature gauge?
Being in a '52, I'm sure its used to burn some rubber. Do you do burn outs in drive?
Did you rebuild the transmission, or install the pressure regulator assembly and the TCC function that is in the pump, as recommended a few years ago?
Have you checked the electrical connections on the trans, make sure they are clean and no corrosion.
Do you have a transmission cooler or a transmission temperature gauge?
Being in a '52, I'm sure its used to burn some rubber. Do you do burn outs in drive?
Did you rebuild the transmission, or install the pressure regulator assembly and the TCC function that is in the pump, as recommended a few years ago?
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other ideas?
Thread Starter
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Laughing Gas
Joined: May 2015
Posts: 826
Likes: 21
From: Golden, CO
Have you checked the electrical connections on the trans, make sure they are clean and no corrosion.
Do you have a transmission cooler or a transmission temperature gauge?
Being in a '52, I'm sure its used to burn some rubber. Do you do burn outs in drive?
Did you rebuild the transmission, or install the pressure regulator assembly and the TCC function that is in the pump, as recommended a few years ago?
Do you have a transmission cooler or a transmission temperature gauge?
Being in a '52, I'm sure its used to burn some rubber. Do you do burn outs in drive?
Did you rebuild the transmission, or install the pressure regulator assembly and the TCC function that is in the pump, as recommended a few years ago?
Yes, running tranny cooler.
Not so much a burnout truck pushing the dually rear-end. Healthy motor though with great exhaust tone (headers and Raptor mufflers).
Don't know anything about the regulator or TCC you refer to??
Logistics Pro
Joined: Aug 2014
Posts: 3,558
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Don't know anything about the regulator or TCC you refer to??
I believe the stock plastic one can overheat/melt, specially if trans is used hard, and doing burn outs in D not 1.
This might be for overdrive, not torque converter lockup.
From what I recall, if/when this part fails, it will stop fluid from the TC lockup releasing. It's a small part, that could be the cause of your issues. Its located in the front pump assembly.
But, Before diving into trans, I'd focus more on the electrical. Inspect the inside of the EEC for bad capacitors.
DO NOT use an older EEC. Your 1995 EEC has diodes that were not in 1994 and older EECs. The solenoid pack on 1995 E4OD does not have diodes, and can cook/fry 1994 and older EECs. 1994 and older have diode in trans, not EEC.
Do you have the ATSG E4OD document? It will have specific trouble shooting procedures for solving your issue. I'll find it, and see what it says.
Logistics Pro
Joined: Aug 2014
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Now, hopefully your truck is still drivable, you can do the following "Drive Cycle Test", and attempt to get a code set.
Thread Starter
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Laughing Gas
Joined: May 2015
Posts: 826
Likes: 21
From: Golden, CO
thank you!
But, Before diving into trans, I'd focus more on the electrical. Inspect the inside of the EEC for bad capacitors.
DO NOT use an older EEC. Your 1995 EEC has diodes that were not in 1994 and older EECs. The solenoid pack on 1995 E4OD does not have diodes, and can cook/fry 1994 and older EECs. 1994 and older have diode in trans, not EEC.
DO NOT use an older EEC. Your 1995 EEC has diodes that were not in 1994 and older EECs. The solenoid pack on 1995 E4OD does not have diodes, and can cook/fry 1994 and older EECs. 1994 and older have diode in trans, not EEC.
Do you have the ATSG E4OD document? It will have specific trouble shooting procedures for solving your issue. I'll find it, and see what it says.
Thread Starter
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Laughing Gas
Joined: May 2015
Posts: 826
Likes: 21
From: Golden, CO
Much appreciated!