P0303 - 98 Explorer not a simple fix

[Dwood1968]

Hey all, a while back I started getting error code P0303 and I can't seem to get rid of it. I have already removed and cleaned all of the fuel injectors, replaced the #3 spark plug wire as well as the spark plug itself. When re-installing the injectors I also switched the #3 with another cylinder to rule out the possibility of a bad injector even after cleaning, but still the misfire is in Cyl 3. I have also replaced the fuel filter and despite all of this I'm still missing. Has anyone had any similar experiences? Or possibly know of the next place to check? I would think that if my coil was bad I would see a miss in more than just Cyl 3, but maybe that is the next place to check? Any help would be appreciated!

 

[Brandon96]

Hey all, a while back I started getting error code P0303 and I can't seem to get rid of it. I have already removed and cleaned all of the fuel injectors, replaced the #3 spark plug wire as well as the spark plug itself. When re-installing the injectors I also switched the #3 with another cylinder to rule out the possibility of a bad injector even after cleaning, but still the misfire is in Cyl 3. I have also replaced the fuel filter and despite all of this I'm still missing. Has anyone had any similar experiences? Or possibly know of the next place to check? I would think that if my coil was bad I would see a miss in more than just Cyl 3, but maybe that is the next place to check? Any help would be appreciated!

I had the same thing, Except Cyl #4. May I suggest taking the Coil Pack to Autozone they'll test it. From previous experience I believe they measured the resistance in ohms and mine was like .02 under the bottom number for normal, and it caused a miss when I was off throttle or I was on it very lightly.

 

[Dwood1968]

Thank you Brandon for the quick response, I will see if I can set up a coil test with my local Autozone.

 

[ranger7ltr]

What is the fuel pressure while under load?

Even after cleaning the injectors and changing the fuel filter I would check the fuel pressure while under load just to see if the fuel system is keeping up with the demand of the engine...

I have had a misfire that was either a clogged fuel filter and/or a dying fuel pump...Eventually installed an electric fuel pressure gauge in the cab to monitor the system and replace a clogged fuel filter and a dead fuel pump...

 

[2000StreetRod]

Compression test

Check the compression on cylinder #3 and compare it to the other cylinders. Maybe it is weaker.

 

[Dwood1968]

Well are you ready for this? Myself, being a Chevy guy, assumed the cylinders were numbered:
6 5
4 3
2 1

When in fact on this Explorer they are numbered:
3 6
2 5
1 4

Long story short, this was my issue. I pulled the real number 3 spark plug and found it to be covered in oil. I then replaced it and took her for a test ride and she ran like a top.

I could have solved this problem much sooner had I looked up an engine diagram before I started. Thank you for the tips guys, but the problem was my own stupidity.