Stumped.

[IMINYOURCHAIR]

97 expy 288k miles.

what started as a miss from a stop light turned into a random trans slipping sensation. but then I noticed no rise in revs with the loss of power,

I have checked the ignition side of things and found nothing. I'm not hearing a vac leak and the pcm isn't throwing a code for one either. fuel filter has been changed as well. looking at live data the fuel trim seemed to get pretty high in the positive range when I was WOT. but I couldn't pin that against the MAF reading or TPS reading as I have learned the program I have is limited with how many PIDs it can plot at once.
The misfire monitor detected one single miss on 1 and 5.

when I did the test I started off with accelerating from 50 to whenever the truck shifted back to third. when I did a 0 to 70 I noticed an odd sound either in the engine or trans. kinda like someone dropped a walnut on a thick tin roof. the "slipping" feeling was present when this happened. it doesn't seem to be limited to one gear but it doesn't feel like a misfire does.

The only thing left to check is fuel pressure but I really need to see it when I am under heavy throttle at speed.

 

[BIG GREEN FORD]

5.4 or 4.6?

 

[IMINYOURCHAIR]

/facepalm forgot

4.6W with the 4R70W trans.

 

[JUST4FUN]

I would go through the Egr ports on the intake

 

[BIG GREEN FORD]

4.6 are known for there clogged egr ports. It could be that coil pack mime went bad and all the shops I went to thought it was my tranny something told me to change that coil pack and it solved my proplom. It was on my old 4.6 expy

 

[IMINYOURCHAIR]

I will check the egr ports I remember cleaning them out when I did the intake gasket replacement. not throwing a code for insufficient flow though.

I am leaning on failing CP. was at store waiting on something idling with ac on so I had to rev it to just past 1200 revs and I noticed it had a skip randomly here and there. this wasn't happening a week ago.

 

[BIG GREEN FORD]

Im 101% if your spark plugs and wires are good I'm sure it's your coil pack it makes it feel exactly like the tranny sliping.. From experience. Not a guess. 1 and 5 are on the same CP also,.. so I'm sure its your coil pack

 

[IMINYOURCHAIR]

yeah, I had noted that. too bad the program isn't showing me 7 or 8 misfire pid. I will see if I can find a known good one to test before I buy.

 

[IMINYOURCHAIR]

hmm, the issue seems to be regressing. Maybe I can wait till it gets worse then continue the diag so I can make a proper purchase to fix it.

 

[IMINYOURCHAIR]

alright, i finally got pointed somewhere. i have set a code. p0308, going to check the wire thoroughly later this eve when its not 100F out

 

[IMINYOURCHAIR]

dbl post;; deleted text

 

[IMINYOURCHAIR]

wire is good. some minor chafing but nothing that's causing a voltage leak. did find an exhaust leak at the manifold. 4 and 8 have a stud broken off.

 

[IMINYOURCHAIR]

swapped the two wires for 2 and 8 to see if there was a voltage leak within the coil. no change, I did get a count on misfires though. I still can't see 7 or 8 but I got 18 on 2 and a total of about 260 total misfires counted. I am going to let the exhaust cool so I can reach my hand around the egr piping to remove the number 8 boot and swap that with another to see if the wire is the problem. I don't really want to have to pull any plugs as I cant afford to blow one out.

 

[IMINYOURCHAIR]

alright, I was going to swap two wires around but when I pulled the #8 off I inspected the inside of the boot to find it corroded. the plug was also corroded but the well is dry and mostly clean. cleaned the corrosion off and test drove it again and got one single misfire out of 10 miles of driving but it was on number 5.

so, problem solved but the odd slipping feeling is still there.

 

[Bowesmobile]

This sounds like spark knock because of timing. Its a loss of power without a mis-fire. These motors are notorious for it. I didn't know that until I owned one and mine does it when you romp on it hard.

 

[IMINYOURCHAIR]

hmm, I will do some research on it, what can be done to fix it?

 

[IMINYOURCHAIR]

also, if it matters, I am using, from what I can tell, factory motorcraft coil packs. if not original they are at least oem

 

[BIG GREEN FORD]

Here's what I would do, replace wires. Get a lot of eelectronic grease for both ends (to spark plug and coil pack) look for motor oil or water in your wires (where is connected to spark plug). Wires will not give codes. And I never heard of the 4.6 being notorious for anything besides being the best engine for lasting the longest. I had one I sold for 1600 last year with 367*** miles and running strong

 

[BIG GREEN FORD]

If you are not sure that your coil pack is bad swap it to the other side and see if the codes change.

 

[IMINYOURCHAIR]

well, now I am not reading any codes, after cleaning that boot I have driven about 30 miles, usually it took one good hill to make it miss and start flashing the cel.
The wires and plugs are still practically brand new with only 11k miles on them. also, I am not into the $$ enough that I am going to throw parts at it. My next move will be to actually swap the number 8 plug wire with number two and see what happens. seeing that 2 and 8 fire at the same time I can leave the coil pack alone for the moment.

If that doesn't give me anything I can reluctantly pull the plug and inspect it but I believe I only got the plugs in by luck as I had no idea about the thread problems in the AL heads. I guess I know better than to over torque things.

So, this week sometime, I will:
1. swap #8 spark boot with #2 boot and watch for the P0308 to turn into a P0302.
2. inspect and clean spark plugs, add dielec grease.