1987 F-150 w/ 4.9 EFI .... Starts and runs perfect for about one minute, then skips a time or two, then progressively runs worse and worse until it's breaking up too bad to drive. Have changed oxy sensor and ect sensor... switched MAPS but with no affect. Engine has about 50,000 original - sat parked for years after an accident. Has run fine since I bought it in the spring and I've put several thousand miles on it. At times it will smooth out and run fine but not for long - maybe a few miles.

 

Check fuel pressure. Possible plugged catalytic converter?



2000 XLT Flare Supercab Sport 5.4-Auto-355LS-Tow pkg-Bedrug-Xtang Tonneau