P0308 code an update

[bookbinder]

:exp:Hi all! Have been chasing a P0308 (cylinder 8 misfire) code now on my 02 Limited for about four weeks. Here is the background and what I found after 4 weekends of beating my head against the wall.

1. changed the plugs
2. oil and filter
3. fuel filter
4. lucas in the tank
5. replaced air filter
6. cleaned the TB with a TB cleaner

While changing the plugs I did notice about 1/8" inch of oil in #8 plug well. Of course this concerned me (not having owned this truck very long). I checked with the local Union Pacific mechanic as they own a lot these trucks and he said the oil was probably from leaky VC gaskets.

1. Replaced vc gaskets
2. Swapped #7 coil pack with #8

P0308 went away for about 2 weeks. Truck ran great. Wife drove to Noel, MO for a float trip and sure enough SES was back on. Starting to think the worst (i.e., burnt or bent valve, low compression, bad cam, leaky intake).

After spending another weekend on this forum and chasing around in the F150 forum I found a thread that discussed high temperatures in the rear of the engine compartment. This got me thinking about coils breaking down AGAIN.
I continued searching the forums until found the post and they made mention of replacement boots. I searched my local NAPA on line and they do carry HIGH TEMP coil boots and springs in their Belden line.

1. bought high temp boot and spring
2. pulled #8 coil and cleaned using CRC electrical parts cleaner while holding coil upright and spraying cleaner on a q-tip on the coil blade...it was filthy. The boot was cracked in several places and was soft and spongy (probably from heat and oil contact) swpped #1 coil with the new boot and spring (sprinkled generously with di-electric grease) to #8 cylinder and the old #8 coil to the #1 cylinder using #1 boot and spring. Be sure you use silicone di-electric grease on the blade of the coil and the spring and inside the boot where it connects to the plug. After inspecting the rest of the boots they are all soft and spongy probably OE.

Hooked up scanner and started driving all day. Short runs, long hiway runs.

NO CODES at all. Truck runs great. I am ordering 7 of these from NAPA @
about *12.00/ea.

Don't over look those boots when doing a tune or chasing an intermittent single cylinder misfire. This is a great forum. I will be Elite next month and thanks to everybody who posts. Rick

 

[cruzzen]

Have you had anymore trouble since you did that with the car

 

[bookbinder]

Not at all. When I looked at the rest of the boots they were real soft and spongy. No wonder it was missing.

Rick:exp:

 

[Funphil]

P0308 code - BAD PLUG BOOT

BOOKBINDER, you are absolutely correct! I have a 2002 Explorer V8 and same P0308 code showed up and I suspected a bad coil or plug. I too switched the coil with another cylinder coil, and changed my spark plugs. Sure enough, it wasn't until I changed the boot (I think I paid $4.95 for one), that the problem was fixed. The truck runs fine and the code went away and never reappeared.

 

[Johnny Glenn]

Great post - a money saver for sure! Start with inspecting the boots - the wire inside is a likely culprit, corrosion etc. There are about a half a dozen things that can cause a cylinder misfire code and this is a great place to start and hopefully end w/ the fix!