Little info on the truck, 01 Dodge Ram, Cummins with approx 147K miles on it. When it's cold out he starts the truck and it idles ok but if you attempt to raise the rpm at all it makes a horrible noise like a miss, blows crazy amounts of white smoke out the tail pipe. Holding it to the floor only gave 2200 RPM. Then it would drop down to about 1600RPM on it's own while still holding the go pedle to the floor. If you then let off the pedle and get back onto it it would raise rpm again and drop off. Seems weird for it to be hunting like that and not wanting to rev up. After the truck warms up it seems to run OK. Anyone got ideas? Exhaust rotted off so the only mods are a 4" cat back. It's a company plow truck. Thanks.
Went and talked with my buddy and their mechanic today. They have tried fuel conditioner. Replaced the lift pump. Fuel filter is pretty new, been changed a few times. Picked the truck up down south and when they went to pick it up it was already running waiting for them. Before the truck is totally warm you can be driving down the road when all of a sudden it loses speed/rpm. Turn the truck off, restart and you are good to go again for a bit of time. Some night the truck will go out plow flawlessly others it's a PITA untill it's warm. What's the electrical system like on these trucks?? Would be nice to try it out with a scanner hooked up to check injection pressure and timming.
That injection pump won't tell you injection pressure. But it will tell you timing. New doesn't always mean good, especially with Dodge/Cummins track record with lift pumps. I have heard of them failing HOURS old.
I would look more towards an electronic issue, like a crank sensor, or a bad fuel injection pump electronics.
Truck should have a digital odometer. Cycle the key on/off three times and watch for codes at the odometer.
Just got back from the shop and found P 0500 P 1693 Could a speed sensor cause this? Would think not because the truck is in park and it stumbles and drops rpm when cold. Guy tried it today. Left it running to warm up then took it for a drive to get some parts. Ran fine.