Sorry for the wall of text below but I wanted to explain everything I could.

I bought a 2008 Quad cab automatic 4x4 with the 5.7 hemi a little over a week ago with 10600 miles on it. I noticed that the truck has a miss that is very easy to feel in the 1500-2000 rpm range. I have checked for codes and none are stored and the check engine light is not on. The miss is there at any speed, as long as the rpms are low I can feel it vibrate and you can hear the engine chugging from the exhaust. It almost feels like I am running on 7 cylinders. It also seems to be related to where I have the throttle positioned. If I push it past a certain point it seems to even out (which also usually pushes it past 2000 rpms though).

I took it to the dealer and they diagnosed it as a seized clutch fan. They put a new one in today and said problem solved. On the way home the computer was telling me I was getting 15.4 mpg, which is better than the 12.1 it was stuck at since I bought it. Now the fan appears to work as intended but it didn't fix my strange miss.

I picked up a boat today (maybe 3000 pounds or so) and the truck was really having a hard time pulling it. I could barely get up to speed on an incline and the miss seemed to be there the entire time.

So, I figure that the miss is always there but not as easy to feel once rpms get past 2000 rpm and the truck isn't hauling something. The truck seems pretty powerful to me but that is coming from someone whose last vehicle was a Jeep Grand Cherokee with the big 4.0 . Has anyone had a similar problem? It is under warranty and it might be quicker to point them in the right direction rather than have them throw parts at it until it works.

 

I would agree the mis is likely there when on the gas as well, it is more eveident at lower speeds because MDS is kicking in and your issue is with one of the 4 cylinders that run during MDS mode.

Plug, wire or coil would be my first guess. If you are truely getting a mis fire you should throw a code for it within 50-100 miles of the issue starting.

Do not go crazy of this though, just take it in. If it is the obvious they will be able to fix it. Warranty is a wonderful thing.

 

You're probably just feeling the MDS...if a miss was bad enough to feel at those rpms you'd have a code even if it's just the random miss code.

 

After reading another thread I am wondering if that is what is going on. I will have them take a look at it. On the interstate it would be fine, in a hilly neighborhood driving 15 mph or slower it just sucks and makes the truck sound sick and shake to death.

 

If you know someone with a tuner see if you can borrow it....disable the MDS and see if that helps. Or buy a tuner.

 

Hyazakite Have you fixed that mis? I'm having the same problem.

 

Drive it in tow/haul mode. This disables the MDS and will rule it out as the problem.

 

yeah my ram does the same thing.. It drives me nuts sometimes.. especially cause my flowmaster exhaust cuts out when the MDS kicks then its quiet as a mouse.. I really need a tuner.. haha

 

The company I work for makes a good tuner for your vehicles.

https://www.sctflash.com/Products/un...nce-programmer

I'm a web developer for them, and I have a 2005 JGC 5.7L that is having serious issues with cutting out between 1500 and 2200 rpms in all gears. I have to floor it to get it out of that range. I brought it in to the dealership for a diagnostic, so we will see what they say.

I love the thing, but if I don't get this figured out soon, I am gonna trade it in on an f-150 4x4

 

So I just got the dreaded call from the dealership. Blown cylinder head. Gonna have fun this weekend!!! I'll take pictures and post a walk through.