Hey guys, Im a newbie so go easy on me. I have an automotive background so Im no dummy when it comes to troubleshooting and diagnosing problems. What really shakes my hair out are "intermittants". I have an instance in my 01 F150XL 4.6 Triton that has me a little fuzzled. I have only had it since Oct of 04 and about December it started missing in the more common sense, uphill under a load about 55 mph. Well it didnt do it all the time so I thought well I still have a warranty, (aftermarket) that I can take it in under. Well my local dealer said they couldnt find the problem since the SES light wasnt on and there were no history codes. The SES light had never popped on at this point. They informed me that it needed 3 Service updates on the PROM. I really didnt buy that but I thought it could make sense. Did that and no dice. Money wasted. Recently I got the SES light to come on and it stored a P0307. Cylinder 7 misfire detected. So, I made plans to replace the plugs first since I had already taken all that apart and inspected but didnt have the funds to fix at the time and found that the plugs werent in the greatest shape. The coils all passed visual inspection. I noticed several times that when it starts to miss, the theft light in the instrument cluster flashes, kinda like when you have the key off. I tested to see if it was just a coincidence but it did it every time I felt it miss. It misses pretty hard when it misses. Sorry for the life history but thought that would be more that enought background on the problem. I replaced the plugs today with Autolite AP764 @ 0.055 gap.

Later
Dale

 

YOU have either a bad boot on that #7 coil or a bad coil I would try the boot first only about 4 dollars and make shure you use a generous amount of dieletric grease on all the boots when reinstalling. if that does not cure it replace the coil.

 

Well let us know if the new plugs fixed it. If that doesnt do it, then look at the coils or the boots.

I have never heard of the THEFT light flashing while driving though, it should not light up when the truck is running.

Good luck anyway.

 

Well guys, the plugs didnt completly fix the problem but the truck does run better however. Throttle response has improved as well as the miss being "slight" at part throttle, 45-55mph. Is the boot a part that only dealers sell? The local Autozone, I know I know, said that they are only sold with the new coil. I figured it was like a bolt. If you can remove it, you can buy it. I am gonna try to load some pics of the plugs I removed. I wanna try to get them all in one image to save space. Number 4 had deposits built up on its ground electrode. From what I dont know. Maybe cheap fuel. Number 7, the one that set the P0307 code had rust on the tip and around the outside of the boot from the hex part of the plug. I thought transient voltage maybe? I cleaned it off very well and put it back in. In my initial inspection of the boots and coils, I found no carbon tracking or cracks. I even took the boots off and inspected the contact springs. Everything checked out with what I had to work with. I do want to check the coils with my handy dandy meter but I cant find any tolerances for measuring them. Are they measured the same as a tower-type coil? Thanks guys.

Dale

Oh, I do want to reinterate that the theft light DOES flash, well maybe a blink, while driving on occasion that seems to coinside with the misfire. So any theory will be taken into great consideration.

 

Hello Dale,

I'm also new to the forum. See "New to the Forum" The Haynes Manual states the tolerances 0.55 on primary and 5500 on the secondary. I just posted a similar case and I'm getting ready to do a tune up on my truck but before I do I wanted to check the resistance on my cop's as well.

 

Hey thanks 5.4. I havent had much time to browse other threads on here so 'preciate bringin that one to my attn. I will give it a look-see. Good luck on the tune-up. I need to snag a manual for my truck myself.

Later

Dale

 

I'm curious to see what you come with for readings on your cop's. maybe yours will differ slightly as mine do. I don't really understand resistance that well but if the manual shows me how to do something and gives me specs and don't do to bad.
If it doesn't read exactly as stated in the manual is where I run into problems though. What's acceptable, what's not? Haynes says that if it doesn't read 0.55 / 5500 they're out of spec and trash them?

Sean

 

There is an acceptable range for the COP resistance, but I do not recall it at the moment...

 

Here you go:
https://www.f150online.com/forums/sh...t=testing+coil

Although this is for the 5.4L engine...not sure if it makes a difference for 4.6L vs 5.4L ???

 

Hi Johngs,

Thanks a lot! That's exactly what I've been trying to find out for the better part of four days now (since reading it in Haynes). I thought it was strange that they all read the same (pretty much). I must have a bad silicone boot then because the plugs in mine are new and the coils check out. If this doesn't work, I'll have to break down and pay Ford to run their "WDS" to find the problem.

Sean

 

Would anyone know what might cause the theft light to blink while driving?