P0303 2002 Ford Explorer Cylinder Misfire Diagnosis and Fix

[JoeBoomz]

Figured I'd post this up for people who are learning. We all were there at one point.


2002 Ford Explorer Limited, 4.6L V8 (2-valve). 190,000 KM (~118,000 miles)

Last night on the highway the "service engine soon" light came on and the engine started a slight shudder. Pulled the code at home with the XCal 2 that I use to tune it, and got a P0303 FALT CYL 3. MSFR DET CY 3.

Here are the cylinder numbers:

FIREWALL
4______8
3______7
2______6
1______5
RADIATOR
(passenger side on left, driver side on right)


On the 02 Explorer, the air intake and tube is on the passenger side, right above Cylinder 3. So I started by taking it off.

I swapped spark plugs between 3 and 5 (driver side has very easy access).
I swapped the ignition coils (COP's) between 3 and 6.
Reassembled air intake and tube, and test drove.

(Use different cylinders to rule out spark plug vs. coils. If the problem does not move, it's an injector or wiring issue.)

Engine still shudders, code I get now is P0306 (cylinder 6).
At this point the spark plugs, wiring, and fuel injectors on 3 are ruled out and the coil is suspect.

Moved coil from 6 to 8 and tested again. Confirmed new code P0308 (cylinder 8). 100% sure the coil is bad now.

Today I stopped at a junk yard and pulled a pair of coils out of an 07 crown vic, same part numbers on the top. All I needed to bring was a 7mm socket. The coils were $11 each. Got home, swapped #8 with a coil from the yard, and problem is solved.

This sure was a nice easy $11 fix to start the year off! Less than an hour of work to resolve.


I hope that's all my Explorer needs this year; it's getting up there in miles ;)

[Mr. Man]

I'm having similar issues with our 2003 Aviator, (4V-DOHC) but have no codes.:mad2:

I've done the transmission flush and added a modifier. Changed the plugs, fuel filter, air filter, cleaned the MAF, throttle body. Next up is to replace the coil packs. We bought the truck used so at 140K it can't hurt to put new ones in.

After the above the truck ran fine for about two weeks, then the shudder started up again. It got real annoying while driving in the rain last weekend. It seems worst at about 60mph but I notice it at almost all speeds above 30mph or basically once the truck reaches top gear. If COP's don't work I'll try and figure out if it's an injector acting up.

Any other things I can fart around with.:confused:

Wish you diagnostic guys didn't live a bazillion miles away. I'd supply the beer and BBQ :beer:

[JoeBoomz]

Do the problems go away when you turn off the overdrive (button on the shifter)?

If so, I'd blame the transmission. Or more specifically the torque converter and it's lockup. Test the vehicle in 2nd and 3rd (if 3rd is an option on the aviator shifter - I can't remember). See if you can reproduce the problem in all other gears at similar rpm and throttle positions (keep your eyes on the road!!!)

The motor will "work" the same amount at 3000 RPM regardless of the gear you are in, given the same air amount and throttle position. If it's an issue on the motor side, you should see issues in all gears.

Changing the COP's can't hurt at that amount of miles but I don't think it will solve the issue

PS: I've wanted an aviator for years, they are gorgeous vehicles with an awesome motor - all they're missing is 4x4, which I have (and have needed) in my 2-valve explorer.

[Mr. Man]

Talking the shudder over with my mechanic today we are thinking it maybe a cracked COP as the shudder gets worse in wet conditions. He thinks one of them may be arcing.


By the way the Aviator is AWD. If you can get your hands on a Kitty Hawk edition they are pretty nice.