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Discussion Starter #1
I haul for a living with my diesel 3500 PM and have about 130K miles on it. The power loss typically happens after I get back on the highway after a 5-10 minute stop. I try to bring it up to speed on the entrance ramp but can't even reach 50 mph. If I need to commit to getting on the highway at this point I drive with the flashers on at 45-50 mph with the peddle to the floor. Even lower speed if it's up hill. In about five minutes it's back to normal. There's no dash indicators telling me there's an issue. Prior to the stop I'm traveling at 70 mph with a normal amount of throttle. This will happen several times in a day or two then its good for a month plus. I had a dealer pull the codes soon after a string of the events and there wasn't a clue. I've spoken with several service managers and none have heard of the issue. I test for acceleration prior to getting on the highway now and will pull over before mixing with the traffic. Just idling for a while will make it normal again.
 

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Interesting symptoms. It seems to be acting like low/no turbo boost perhaps, but that has a code. Plugged exhaust would do it but throw a code too. Injectors not opening is the only other thing I can think of that might not give a CEL. Doing that would be signaled by the Engine Management Computer and be a limp home sort of action. With no spark the diesel has to go if it gets fuel and air. How it can cure itself in 5 minutes is a real mystery. You are the first with this symptom and no codes BTW.
Try disconnecting the ground side of the battery for 1/2 hour or so to reset/restart the computers. The dealer did confirm you had the most recent computer flash/update right?
 

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2014 Ram Promaster 2500 159" diesel
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You give a diesel fuel it will run. The modern diesel has electronics that could go bad, but they should throw a code when bad. Since you have no CEL showing my guess would be fuel filter, check it. The last time you changed it, how dirty was it, if it was dirty crud could still be in the tank, check it. Check the fuel lines for a crimp or pinch point this could cause low fuel pressure on acceleration but will run normal at cruise speed.
 

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MMXVI - L2H2 in IN
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Similar? Had an old school diesel that would pull a load up 50-55 and could go no faster, normally 70-80. After messing around with injectors it turned out the fuel transfer pump was failing.
 

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I like both ideas but why does it “cure” itself in 5 minutes or so, repeat for a few times and then not bother for a month? Like you say, fuel filter, check the pump pressure and volume as these are easy and inexpensive. I had a gas pump-in-tank replacement pump that drove me nuts for a year with intermittent no engine power, bought a fuel rail pressure gauge to carry and finally caught it once beside the interstate.... finally, second pump was the charm!
 

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Discussion Starter #6
I replace the fuel filters and the issue isn't tied to new/old filters and I have up to date firmware. I think a fuel pump issue would throw some low pressure code but I don't know this for certain. What is the easy and inexpensive way to check fuel pressure and flow?
A smart guy I know has run into this before in another vehicle. He discovered the inertial sensor for the stability control would throw crap data and the response is power limiting. Codes don't get stored for this. I don't recall the ESC indicator coming on and I believe I would have noticed it. I'll turn the ESC system off by holding the button for 5 seconds the next time this happens to see if keeps it from happening a second time. What other systems in the PM can cut the power back and not record the incident?
 

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Good thought. Fuel pressure for these diesels is something like 15,000 psi (that is not a typo!) so unless you have some really specialized equipment you won’t be testing much. I have no idea about sensors for that system but the results of failure will be monitored by the ECU. Interesting idea about the ESC system. I believe no code would show. Mine will engage on accelerations as I enter from a side street and attempt to get into traffic in a hurry turning sharply just at the torque level where the front tires would spin. I have yet to see any indicator that it is working but there is a noticeable loss of torque and power. I basically dislike these “save the crappy driver” electronics but we live in a World they are integrated. Oh- with one exception.... the ABS on my BMW motorcycles, apply the brake as hard as you want and it will not low side you. Does that mean I too am a crappy rider?
 
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