Exhaust issue or am I crazy?

[Mako21]

Hi All,

So I have a 2019 Ram Bighorn CC North Edition 5.7L with the 8-speed. About 42k on it. Been having some issues since I got it and some have been fixed. One that has been constant since a transmission valve body was replaced is a “hiss” sound that occurs when the rpms rise during 1st > 2nd > 3rd gear shifts (when engine is cold). I thought it may have been an exhaust manifold leak after doing some research on here and seeing the symptoms (air leak sound, loss of acceleration, mpg drop, etc.), all of which I have. I had it looked at by the dealer nearby and they said all the bolts on the manifold are tight and no signs of an exhaust leak or performance issue. They didn’t hear the sound either, until I went to pick it up and went for a ride with the service director. He heard it but couldn’t pinpoint it. Every person at the dealerships I’ve spoken to have alluded to winter fuel (I’m from MA) being the mpg culprit. I just don’t see how my mpg would go from ~22mpg hwy to like 17-17.5mpg. A broken exhaust flange bolt caused a similar drop in mpg over the summer. Once it was sealed up again, gas mileage was fine.
Has anyone had similar issues or have any ideas on what this could be?

Loss of acceleration
Severe drop in mpg
Hiss/air leak sound
Oily smell from engine when warm

Thanks for any input.
-Mike

 

[Lee Pedrick]

You got 22 mpg in a Ram and you are complaining about 17mpg??? Not being smart but thats great. Do you run MDS all the time? Half the engine is cooler than the other half. This would not be a problem if they shut off every other cylinder instead of half the engine. Just my opinion. I run my 8 cylinders every time I get into the truck. PITA but My driveway skills tell me theres more to that than told.

 

[Mako21]

Both this one and my ‘17 Express got 20+ consistently on the highway. MDS is on, but I don’t usually see it kick in on the highway at 70-80mph though. Usually driving backroads.
The service director thought the hiss sound might be a trans fluid heater(?). But now that the manifold leak has been crossed off the list, some things to point to a torque converter issue. It does shutter at times and jerk a bit. Just trying to trouble shoot.