Loss of Power in the Mountains

[DFrank]

Loss of Power in mountains



I experience sudden loss of power and all sense that the pedal is even connected to the motor. It does not stall but stays under 1,000 rpms while pumping the pedal. Then just as quickly it revs back up, sometimes close to redline, again feeling like the pedal is not even connected, then it resumes normal driving, though it may happen a few more times before really feeling normal.



This problem first reared its head a few times 6 years ago. I wrote it off as contaminated fuel and didn’t experience it again for a couple years.



It only seems to happen on cold days climbing a pass while the truck (transmission?) is not quite warmed up.



The check engine light comes on and the P0700 code always returns. One time there were two other codes that were related to throttle position sensor. I’ll add the actual numbers if I can find them.



I was thinking lift pump, but replacing it didn’t help. I didn’t upgrade, but used the Geno’s direct replacement, which I suppose could still be a little underprivileged.



It is now happening everytime I drive home from the mountains, but never when heading into the mountains. My assumption is that the transmission has time to warm up when leaving town, but does not when leaving the mountains.



The transmission was serviced less than 10k ago and is topped off. It has 150K on it now.



I want to fix this or have it fixed, but I don’t want to drop it off for the old “sorry we could not duplicate the problem”, because they will NOT be able to duplicate the problem.

 

[cerberusiam]

Sounds like an APPS problem under very specific circumstances. That seems to be a typical problem when the under hood units get so old. I think you would safe replacing the APPS as first step in the right direction.



The P0700 is transmission fault. You will need a scanner capable of reading the PCM to find out what it really is. It may or may not be a clear indication of a transmission part failure and may likely be symptom of an APPS failure.

 

[LNaugle]

i agree... sounds like apps. could cause trans code also.

 

[Prairie Dog]

Good source for APPS Timbo APPS

 

[AH64ID]

Would a faulty APPS signal take the trans out of gear? (assume it's in N based on the reported rpms)

 

[cerberusiam]

Would a faulty APPS signal take the trans out of gear? (assume it's in N based on the reported rpms)

No it sends faulty info to the ECU which tries to react and messes up the governor pressure. It drops OD and tries to downshift to 2nd at the same time when speed is too high and you end up with a free rev until the ECU figures it messed up and resets the gov pressure.



The ECU sets gov pressure based on APPS and wheel speed, when things don't match its table of vlaues it freaks out. Pumping the pedal really gets it out of synch at times.



If the OP hasn't serviced the gov transdcuer and solenoid recently or upgraded the solenoid it is hard to tell what causes the total lack of connection in the trans control. Could be APPS or the trans pieces.

 

[DFrank]

Thanks. i have not serviced the gov transducer; I don' even know what one is! My solenoid should be upgraded? what does that mean.

What is the APPS? Can I replace it myself?

Dave

 

[Prairie Dog]

Yes you can replace it yourself. Check out the link I provided above.

 

[cerberusiam]

APPS is Accelerator Pedal Positon Sensor. Its what tells your engine to rev up and down. It is nothing but a dual sense potentiometer that feeds the ECU a voltage to tell it how much to fuel. When they get a worn spot on them the voltage drops and the ECU goes into a reset loop trying to recover. If its down long enough the engine goes back to idle. Frequently you get a dead spot that won't allow acceleration and you get the codes.



It is under the blck cover on the left front on the engine, easy to replace. The previous link is a better cheaper alternative to the OE offering.



Transmission control is influenced by 2 electronic pieces, governor pressure transducer to read pressure and a solenoid to set it. Its a feedback system and constantly adjusting as the the accelerator pedal is moved. The cheap OE pieces start failing around 40k and giving inconsistent readings. When the solenoid sticks high or low too long the PCM stores a code indicating a fault. You need a scanner capable of accessing the PCM to retrieve those codes to verify the problem. Just guessing that is the issue as it is the commonest one but the output shaft speed sensor could be causing it or even a rationality code for lockup could be the source.



The stock pieces are here at a good price.



A500 42RE A618 46RE 47RE 48RE Transmission governor pressure sensor Transmission solenoids

A500 42RE 44RE A518 46RE A618 47RE 48RE transmission governor pressure solenoid 4617210



or the upgraded OE style here



Dodge "RE" Model Borg Warner Pressure Solenoid Kit



or the GM style upgrade to never worry again



#ad




can be found here PATC 46RE 47RE 48RE Transmissions, Performance Transmission A518, 518 by searching the page for #REC.

 

[DFrank]

Thanks. I ordered an APPS and am wondering if I should go ahead and do the solenoid too.

None of my problems occur unless it is cold out and not fully warmed up while working hard. It can pull hard all summer and do hills fine if its had a proper warm up.

Maybe the solenoid is challenged by cold transmission fluid, but does ok once it is warm?

 

[cerberusiam]

Maybe the solenoid is challenged by cold transmission fluid, but does ok once it is warm?

Yes, that is a possibility.

 

[DFrank]

So to replace the solenoid, it says to replace the gasket and filter. I did that this summer; I assume the filter will still be fine and the gasket is pretty beefy. Can I plan to re-use the gakset, or do i need to replace that?

I couldn't find it on Geno's or the site I've ordered the solenoid from. Can someone suggest where to get it? I guess I should have it on hand before dropping the pan.

Thanks, Dave

 

[LNaugle]

do you have the mopar reuseable gasket? if not i would get one and no worries from there... i would still change the filter... they never get changed enough anyway.