I'm having power loss coinciding with poor fuel economy while accelerating and cruising. The truck is a 2015 ram 1500 5.7 125k miles no codes. It's not there when the truck is cold and it gets worse on longer trips. To the point where it's almost non intermittent. Removing the gas cap "seemed"to alleviate the issue albeit not solve it completely. I also found it odd that I drove about 20 miles with no gas cap on and never got a light. I have checked codes with torque and a Bluetooth adapter and none are logged.. disabling mds via manual shift doesn't not have a noticeable effect and it does not feel like misfire. Any ideas on where to start?

 

Try disconnecting the front O2 sensors, and see if the problem goes away. That WILL set a few codes.

 

thanks I'll do that and try it out. I've been super busy and haven't been able to give her any attention I did have to drive it yesterday and I don't know if this changes anything but I really got after it and it did finally throw a code for a cylinder 5 misfire. It then ran really rough for about a half a mile after which it cleared up and ran normal.

 

This might have to do with the EGR opening and closing. Does this issue happen more often when cold?

 

Truck runs fine when cold, full operating temp I get power loss poor mileage and surging. The only way to get it to throw a code is to WOT at 4k rpm. Then it starts misfiring horribly for a few miles. The light will only flash under extreme acceleration though. I moved the plugs/coil around and the misfire stayed. I'm convinced it's a failed lifter that ate the cam, I really want it to be something else though so I'm open to ideas. Catalyst temps are 1500-1600 degrees 90 degree day after beating on it and misfiring so I don't think it's the cats. I sat at a light the truck barely running with no CEL.

 

So, I'm just going to bring it in to a trustworthy local shop next week, I just haven't had the time to work on it myself.. Would I be able to put a 5.7 into it from a 2019 without too much fuss or are they quite different?

 

Unplug the front O2 sensors, and see if it runs any better. If you had cam/lifter problems, I would think that would be a consistent problem. (dead miss) PCM should whine about that......

 

Sounds like how my 2013 Ram 1500 with just over 100K started out.

Felt like it was surging, missing etc during acceleration. Tried everything. New plugs, PCV, EGR etc...finally started getting misfire codes on #5. Swapped coil pack from 5 to 3 and code stayed on 5. Heading to the shop tomorrow for further diagnosis including injectors etc.

Bad part is that this has been the story for many folks having the dreaded 5.7L cam/lifter failure. When it first starts, and the damage isn't that extensive, normal driving "feels" normal and issues only show up during acceleration or towing etc..then it gets worse and the misfire codes don't go away (it is not consistent in the beginning, at least not in terms of felt effects).

Looking at a very expensive repair if it's the cam/lifters. Can't sell it in good conscience, dealer will rape you if you try to trade it in. Have to fix it and hopefully drive it for another 100K.

 

The 5.7 hemi does not have EGR. The VVT takes care of the function.