Good morning, I am looking for some help on a problem that is baffling me and my mechanic. I was driving around 2 sundays ago when my truck started shaking really bad and running rough. It would smooth out when I let off the fuel pedal. A few moments later it stalled. I could only get it running if I feathered the fuel pedal and it would only stay running if I did the same thing - I had to two foot it home. I hooked it up to my basic code reader and I got p0300 Multiple misfire codes. I just had a full tune up done within the last 7 months or so with new plugs and wires. Well not knowing where to start, I took it to the same mechanic who did my tune up and previously replaced the drivers side CAT.

Well the computer keeps throwing random codes that always lead to another code.. So far the mechanic has removed my passenger side CAT as it was glowing Red. Replaced my pugs again because they were trashed and put in a new crank position sensor. I stopped by yesterday and they pulled out the crank position sensor and it had scratches on it with only 5 mins of run time. He said that the timing does not appear to be off based on his computer readings. I think we are both at a loss as to what could be wrong here. My next "guess" would be if there is enough movement in the crank to scratch the position sensor that maybe my harmonic balancer went bad?? I've had a harmonic balancer go bad in a older dodge ram and it did not prevent the truck from starting or cause a misfire.... Any direction would be greatly appreciated. Thank you.

 

Pull the valve covers and check for broken valve springs.

 

And don't run it anymore (although that applies more to the '03s). Mine got all new springs last winter.

 

Correct. It is more seen in the 03s but there have been a select few members with 04s that have had the same issue.

running rough/wont idle
having to hold the fuel pedal to keep it running

both are symptoms of a broken valve spring

 

I agree with a possible valve spring problem....