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Discussion Starter · #1 ·
hey folks,

99 Taurus SE Wagon
3.0 (U) OHV
Auto
329K (original engine)
Trans replaced once (knock on wood :) )

Received error codes P0305/0306 Misfire on #5 & #6 cylinders.

I won't be working on this til Tuesday, however, thought I'd ask a question today.

Problem
Car was running fine until last Friday. Parked car Thursday evening with no issues at all. Ran perfect. Fired her up on Friday afternoon and all of a sudden I have the codes spewing out. While the codes were hot in the computer, she ran like crap. I cleared codes and she ran perfect. Clearing codes also took place after engine had warmed to near normal. Drove car all afternoon on Friday and she did fine. Parked and sat til Sunday afternoon. Fired her up again and received the codes again. This time along with backfire on acceleration.

Today I have picked up fresh plugs, plug wires and new coil pack to install tomorrow.

One thing that did occur was weather related. Thursday night we had heavy, heavy rain fall which was around most of Friday too. My thoughts here is that I have a bad (cracked) coil pack and the high humidity seeped into it causing the codes. Even Sunday morning our humidity was pegged @ 93%. So I think I'm on the right track.

Question

Can any one point me to a diagram of the plug wire order on the coil pack? It would be interesting to know if Cyl' #5 & 6 plug wires lined up on the coil pack. I was just thinking if 5 & 6 are teamed up on one end of the pack and the coil is cracked on that end, then it would make perfect sense that both 0305/0306 codes would occur a the same time. Just a thought.

like....
1 2 3 ??????
0 0 0
4 5 6 ??????
0 0 0

1 3 5 ??????
0 0 0
2 4 6 ??????
0 0 0


In the meantime she *is* high mileage and am wondering if there's anything else I should be looking at right now.

Thanks!

Chap
KY USA
 

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I think you are on the right track. Rain / high humidity missfires are virtually always plug wire or coil pack related. I dont remember off hand which cylinder maps to which coil pack terminal, but that info is around here somewhere, but it is pretty easy to trace out the plug wires yourself..... probably take less time doing that than searching here or google.

I would suggest Motorcraft plugs, wires and coil pack versus some no name junk from the discount parts store. Stay away from Bosch plugs for sure. Motorctraft, Autolite or NGK plugs are good for Ford engines.
 

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Discussion Starter · #3 ·
Thank you Jeff,

I might be able to work on her tonight. Either way, I'll post results....

:)

Thanks again

Chap
 

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Discussion Starter · #5 ·
Error codes P0305 and P0306 resolved.

Looks like #6 Plug wire took moisture and arced inside the coil terminal. The photos pretty much tell the story. I'd say the P0305 was a sympathetic code as P0306 was the actual problem. Both 5 & 6 spark plugs showed the backfire scars.

Notice the discoloration of Port 6 on the coil pack. All other ports were shiny brass. You can see the arc in Port 6 and a very shiny Port 5.

Changed plugs, wires and coil pack and an oil change to boot. Go to go!

Noticed fraying on the accel cable at the t/body.... better order one now! :)

Thanks folks,

Chap

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