hello i have a 4.6 remeo. i swaped motors becuse the old motor had a rod knock . so i got another long block and it misses at idle and when takeing off unless you get the rpms up then it has power i changed plugs bought the motor craft ones double platnum ford dealer said they were the right ones i allso noticed when you get on it you can here it pinging any ideas ? thanks for the help kelly ps the motor i found out was out of a 99crown vic so i had to change the timeing cover and valve covers i got tis information from the valve cover on the wrecking yard motor the guy at the wrecking yard said it was out of a 97 truck. someone else must of put in in the truck .

 

You either have a vacuum leak or a problem with the MAF sensor. That's where I would start looking. PCV hose assemblies are known to crack in the elbows. Especially at the rear of the intake manifold.

 

i found out what the problem was i sprayed starting fluid around and found no vac leaks so i changed injectors around seeing if it was a injector but it was still missing on the same cylinders so i pulled the plugs out and did a compression test and hot reading wide open throttle 1 to 8 cylinder readings 150 ,im guessing 20 it didnt hardley move 140,50,150,150,160, same here hardley moved 20 i bought from a wrecking yard they said it was out of a truck and ran the valve cover number it came out of a 99 crown vic someone might of put it in the truck then they said it was rebuilt for 1500 was the price of the motor and i started asking questions and they said ony the top end was rebuilt i saw all new gaskets another thang was they had 4.6 winser gasket set for the motor i found this out when i got home with the motor i called the guy and said there is problems with this motor but the owner isnt in tonight so i going to call tomorrow they said they would have him call tomorrow i found out the motors are a pain to put in lineing up tourk converter and exzaust studs all at the same time first time doing a new ford motor thanks kelly