I have bought a used mustang from a friend with 160,000 miles on it. I have put 21,000 on it now. It started missing yesterday and gave a P303 code for cylinder 3 misfire. I changed the plugs and wires and coilpack. It still misses at low RPMS. If I bring the idle up to 750 RPMS, it runs fine but anything below that it misses pretty bad. What should the fuel pressure be? I changed the fuel filter at 160,000 miles. Any suggestions would be appreciated. Thanks..

 

Fixed it, Put in a new set of motorcraft plugs. Runs great now.