Engine misfire

[Andy Gar]

My 03 Expedition 5.4 With 189K started misfiring a few months ago, it was running rough, the Service Engine light would flash and a ton of codes came on at once including 301 and 307 so I figured plugs and coils. I replaced all plugs and coils with Motorcraft brand and it ran great for a couple of months. Last month it did it again, same codes, same cylinders misfire, so after asking a tech a the Ford dealer I replaced the ECU. So now with the new ECU I only get 3 codes 300, 301 and 307... but it is still misfiring and not running at full power. I replaced the coil and injector pigtails for cylinder 1 because the plastic tabs were broken, but still no change. What next, should I change fuel injectors?

 

[riphip]

Also check your vacuum lines. PCV area, behind batteries, etc. They get old & cause a lot of ignition/running problems.

 

[Hamfisted]

What did you do to cylinder #7 ? You said you had a P0301 & P0307 . You worked on cylinder #1 , but what did you do to cylinder #7 to fix it's miss ?

 

[James Bradley]

I was having similar issues with my 05. I've had it in the shop many times for misfires on several cylinders. I've had spark plugs changed along with a coil or two. Now I'm having the DTC code for timing retard. My mechanic says since my timing chain needs replacing I should have the cam phasers replaced as well. My 05 has 157K. I really like this suv so don't know to invest the money or look for a replacement vehicle. I sure don't want 5 years or more of car payments but at the same time I don't want to keep throwing money into a 15 year old vehicle replacing one part after another. Any suggestions?

 

[Hamfisted]

Well, it's not worth anything on a trade in and really nothing to anybody with it's misfires. Anybody that does any research on the Ford 5.4 equipped vehicles knows the issue with the early 3-valve motors. So if the body is in good shape otherwise, you might want to just fix it and keep it yourself. At least you'll know it's been repaired and reliable. It's about $3k to have a shop do the timing set and oil pump. Tell your mechanic to use only Ford cam phasers, and the Ford or Melling high volume oil pump. Once repaired it should be good for another 150k miles. The bigger problem may be the passenger side overhead cam, if it's been the victim of oil starvation. If your misfire codes are consistently P0303 or P0304, and you've gone through the coil and sparkplug changes on those cylinders, you may be looking at a damaged cam already. But, you never know until it's inspected.

 

[Msport]

If you suspect the fuel injectors, start the engine, using a very large screwdriver, place the flathead on the side of the fuel injector then place your ear on the plastic end, you should hear the injector clicking. If you do not hear any clicking the injector may be bad.