Windstar :: 2002 - Car Running With Blinking Check-engine Light / Code P0306

So I had a serious runability problem back in 2012 with code P0302 (misfire in cylinder 2) and the car was barely running. I changed the spark plugs, which didn't fix the issues. Then changed the coil, which fixed it. URL...But I was a little lazy back in September 2012, the old spark plug wires looked like they were still in great shape, so I left the old wires on. I think they were the original factory wires, they had the numbers of each cylinder printed on the side. Very nice wires!

Fast-forward to the present. Car starts running poorly with a blinking check-engine light. Not good! I check the code and it is P0306, misfire in cylinder 6. So my first thought was: OK, probably time to change the spark plug wires!I changed the spark plug wires. I purchased AutoLite Professional Series wires at Advance Auto Parts, part 97047. URL...Sure enough, the number 6 wire looked like it had a little corrosion inside the end that connects to the spark plug wire. It looked like I was on the right track! Changed the spark plug wires, and ran it. It still sounded like it might be missing on one cylinder. Just a quiet ch-ch-ch-ch-ch-ch at idle. I took it for a test drive. It ran OK at low RPM's, but had no power. When I tested some hard acceleration, sure enough the check engine light came back on. Tested the code and it was P0306 again. Conclusion: not fixed yet.

OK, maybe the spark plug wire was the problem, just the plug got fouled because the wire was bad. I purchased a replacement spark plug for that cylinder only. AutoLite Double Platinum as recommended elsewhere in this forum. Removed the old plug. I'm no expert, but the old plug looked fine to me. Installed the new plug. Tested it again. Still sounded like missing at idle ch-ch-ch-ch-ch. Test drive, OK with low RPM, no power. Tried hard acceleration, got the blinking CEL again. Conclusion: still not fixed - darn it!

Now remember, I just changed the coil back in September 2012. I had replaced it with a coil from AutoZone. The first coil had lasted ten years. So it couldn't be the coil again this soon, right? But... just to be sure, I went ahead and changed the coil again. I called AutoZone and happily it was still under warranty. The previous coil I had purchased came with a 24-month warranty, and I was on month 23 !!! Sweet!AutoZone also told me if I did a warranty replacement of the coil, the new one would come with a lifetime warranty instead.The part number of the coil at AutoZone was part C1312, Duralast Ignition Coil.

Before installing the new coil, I put a little Dielectric grease around the top inside of each connector on the new coil (7 total, six spark plug wires plus the electrical connector). I think this was recommended in my Haynes or Chilton manuals.I am a tall skinny guy with long skinny arms. So I was able to replace the coil without removing the cowl. Last time I had to remove the cowl (to do the intake manifold isolator bolt repair) the cowl had cracked, also some of the clips holding it down broke. So I didn't want to remove the cowl unless necessary. It turns out with my long skinny arms I can lay up over the motor and reach back around both sides of the intake manifold to reach the coil. It is a reach, but it was possible for me to do the job that way.

I removed the three bolts holding the old coil in place. Then I was able to slide the new coil back in there, around the driver's side of the intake manifold. I transferred over the spark plug wires one by one from old to new (as recommended by another poster) so I wouldn't get confused which was which. It worked well to transfer the rear three first. That hold the new coil near the correct location, and gave me more slack to move the old coil further out of the way.Next step was to remove the wire connector from the rear of the coil pack. It didn't want to release. I looked at the old part (from 2012!!!) and there was a little plastic nub back there to lock the connector in place. It looked like there was room to work in a small screwdriver back there to release the lock. So I wiggled a short flat-head screwdriver in back there (with a wide head) and it released. Then I was able to easily remove the connector.

Then I had more slack to move the old coil further out of the way, toward the drivers side and front of the vehicle. And then transferred the last three spark plug wires to the new coil.Then to secure the new coil in place, I carefully installed one bolt by hand, leaving it loose to allow for final adjustments of position. Installed the second and third bolts loosely. Tightened the three bolts finger tight using a short (3") extension and 7mm socket (1/4" drive). Then snugged them very gently using my small 1/4" rachet. The small 1/4" rachet was a perfect fit using the 3" inch extension and the small 7mm socket. Remember you just want the bolts snug, do not over-tighten them.

When I went back to AutoZone to process the warranty return, they had to do some fancy work with their computer to get me the lifetime warranty on the new coil. By default it would just assume the rest of the original coil warranty from 2012 - which was just about to expire. So they made it right for me - but only because I specifically asked about it. By default, the guy had already rung it up their "normal" way, which would not have extended the warranty for me.Another thing that was strange was back in September 2012 when I replaced the original coil, it had worked well for ten years or so! Also, the bottom of it was clearly cracked, so it was easy to see that it had deteriorated and needed to be replaced.