Starting about a year and a half ago, my 2003 F150 started having issues. Randomly the truck would not start or would die when I came to a stop when the engine was still cold. Over the course of trouble shooting I have replaced the fuel filter (multiple times), replaced the fuel pump twice (OEM the second time), replaced the ECT valve and ran enough injector cleaner through it to kill a horse.

After ever parts change, the truck will run fine for a week or two and then starts acting up again. The spark plugs are less then a year old. I have checked fuel pressure. I have cleaned the air intake and the MAS. Still the truck will intermittently not want to start. Then this past Sunday morning it was running very rough upon starting and it popped a P0300 code. I have sprayed carb cleaner around the engine trying to find a compression leak, but can't seem to locate one. I would sincerely appreciate some input on when to look next. I'm getting very tired of this issue. Any and all help would be greatly appreciated!

Thanks! Joel

 

How many miles on truck? I would hook up a vac gauge and see if its high than 15.
Possible causes
- Faulty spark plug (s)
- Faulty ignition coil (s)
- Clogged or faulty fuel injector (s)
- Intake air leak
- Fuel injectors harness is open or shorted
- Fuel Injectors circuit poor electrical connection
- Ignition coils harness is open or shorted
- Ignition coils circuit poor electrical connection
- Insufficient cylinders compression
- Incorrect fuel pressure

Read more: http://engine-codes.com/p0300_ford.html#ixzz3WFa820wi

 

My money is on the sparkplugs. Pull them and number which cyl each comes from and note any that look bad. Not sure what brand you installed a year ago but install new Motorcraft plugs. Also I think you are looking for a vacuum leak not a compression leak.