pardon my longwindedness. 2001 f-250 s/d 5.4 auto. 223k. cops aren't branded. autolite platinum ap103 plugs. returning home yesterday-100f ambient-a/c full blast- truck starts to miss. won't accelerate. limp it on in and begin tests. new fuel pump in jan 18. good fuel press 40+ at idle. truck will idle, but miss a little. just a little. full blast acceleration from idle yields 2.5k rpm and really bucking and missing. will drop back to idle and smooth out. slow acceleration from idle will go to at least 5k rpm. and stay there w/little missing. about 1/4 pedal maybe. full on acceleration from there and back to square one. bucking snorting missing as before. holding the pedal down during this for about a minute and noticed the BACK of the cat converter glowing red. get a coupla lean fuel 0171 and 0174 both banks. let it cool and test the cops. at idle I can detect missing in exhaust note for each cop I unplug and plug back in. do propane/vacuum test. pretty comprehensive. done this before. no leaks detected. pull line from pcv to back of throttle body off truck. ends look pretty good/no splits in plastic hose. pcv valve rattles like a buckshot in a boxcar. can blow thru it both ways. OK. truck has been good before this. not used much; 10k miles in 6 years. got a tps in '13, fuel filter in '14, said plugs in '15, (motorcraft plugs that came out were gapped from .07 to the back 2 at .10.) and well used. this truck has no egr valve, either. and I DON'T know what else to check. I know you will say denso cops and you're right. should have branded cops. have a Lincoln ls that I spent $400 on cops and plugs. high maintenance car, but it runs like a scalded dog. hard for me to believe this truck went from running happily down the road to this in one fell swoop. I am here asking for your help, though, because I can use it. thank you in advance.

 

I cant remember the last time I had a motorcraft coil fail , but I have replaced all of the boots , because of an intermittent miss.
My truck is a 99, with the 6.8 , and I put 25k miles a year on the poor thing .
Boots are cheap , and not hard to replace.

 

thank you for your kind reply, sir. took a good look at the boots and springs when replacing the plugs. lotsa dielectric grease; well, you probably know the drill. I also pulled #4 cop and plug this morning just because of its proximity to the crossover and the boot looked good, still showing grease and the plug well was bone dry. the iac valve is the only thing I haven't really looked at; idle is pretty steady @650-700 rpm w/just an intermittent 'put-put'. you can bet it will be new boots and springs if I go the denso coil route. just looking for more ideas/causes before I pull that trigger. I perused this forums search engine 'till I was cross-eyed yesterday. someone even said they changed the knock sensor and it woke the engine up.

 

bad seal top of the fuel pump. finally blew out.

 

You mentioned above with regard to the PCV valve that you could blow air through it, both ways ("pcv valve rattles like a buckshot in a boxcar. can blow thru it both ways"). I was under the impression that it is a a one-way valve. Seems to me air should only go through when in the open mode?

 

i don't know how this particular pcv valve operates. I have no positive intake pressure, so I don't see how it could possibly blow back into the valve cover. I did find the problem w/my truck and posted it. perhaps i'll look into procuring another motorcraft pcv. thanx for your reply.