[Anthony79]

I had the same problem on my 11 without a code, I changed the VVT solenoid this weekend and the fluctuation in RPM stopped, gas mileage went up, and now the truck responds and accelerates like it should.

 

[Anthony79]

Variable valve timing solenoid. It's under the intake manifold on the front of the block.

 

[Anthony79]

I didn't have any codes either, and mine started getting bad around 130k, and now have 147k, and power was way down. Everyone was telling me it was a vacuum leak or the TC. When I looked at the exhaust pipes I noticed they were getting black, which is a sign you are running rich. The VVT solenoid works with the cam phase to advance/retard the timing. Since it could reach the advance or retard needed, the pcm was adjusting the fuel and air flow to compensate, hence the rpm going up and down.

 

[Anthony79]

I am having this same issue... 2014 Ram 1500 5.7 hemi with 8 speed auto ..started around August out of the blue. I have no CEL and when taken to transmission shops.. they have told me that after hooking it to scanners and driving that the transmission is running normal. They do agree that they can feel and see the RPM surge. I have cleaned the throttle body and the transmission fluids have been checked.. really at a loss right now with no CEL.

Symptoms:
RPM surges around 1200-1500 and is consistent like a heart beat when driving steady at 40-50mph
have noticed a good amount of drop is gas mileage
when driving up a steady hill under low speed there is some shudder when the RPM surges
After about 15 minutes of driving it seems to level off and become normal again.

Try changing the VVT solenoid, it cause RPM surge, ruff idles, and decreased fuel economy, without CEL. Part is fairly cheap, and easy to replace.

 

[Anthony79]

I didn't have any issues at idle, my gas mileage was down, and truck rpm would surge 200-400 while driving down the highway, and the truck would start a small hill. Would also do it a lot when pulling a trailer. I think the part was $35 at O'Reilly.