I have a 2007 1500 5.7, at cold starts engine runs with a #6 misfire P0306 and has a backfire into the manifold. I replaced plugs and moved wires around to see if misfire also moved but it stayed at #6. I had the valve cover pulled off due to someone suggested a broken valve springs, but springs looked good. after about 4-5 minutes the truck runs fine. It was also suggested it maybe a bad or broken lifter.. any advise?
thank you in advance, chris

 

if you have a warranty why not?

 

no warranty bought it used has 45000 miles on it now..

 

Sounds like it's time for a compression test, dealer or preferably a decent local mechanic. That's the one thing that sucked about the "Lifetime Powertrain Warranty" it was not transferable. My '04 that I bought new would still be covered for another year from now and 23,000 miles if I sold it tomorrow for just a $100 transfer fee...

 

had a compression test done with a result of 125 psi in the #6 valve.

 

could it be a lifter?

 

ihave learnt one thing owning a dodge, NEver EVER take it to a dealer, i have nothing but bad experiences and lost alot of money, a local mechanic here is better and alot less expensive, but im with hammer on this one

 

i need to start readin the whole thread before posting i didnt see u had a compression test, my bad, but it could be a lifter, dont know for sure though

 

thanks for the replies, is there anything i might be able to check or look for? the strange thing is when it warms up the truck runs great.. i do have a tap. thats why it was suggested a possible lifter causing the rough running and manifold misfire on the cold starts.

 

The "tap" could easily not be related as some engines have the "hemi" tick. But back firing into the intake indicates to me that you have a lifter problem or at least a sticky valve. Are you changing the oil regularly? I don't normally recommend top end lubricate but maybe this time it would help. I would at least do a oil change to see if it helps.