I've been chasing down an intermittent misfire on a 2000 4.6 liter at work for the past couple days. It never really showed itself consistently on any cylinders, bouncing around between all of them, with no misfire DTCs set. It'd do it on cold start, hot start, at idle, at cruise, on decel, on accel, whenever it felt like it. Relative compression was good, mechanical compression was good - and speaking of mechanical compression, was I ever surprised when I pulled the plugs and found Bosch Platinums. I asked the owner and he said the problem has been there ever since before he had it tuned up with those plugs.

So, here I am this morning, after throwing every test I can think of at this damn thing. I pulled the Bosch plugs and replaced 'em with Motorcrafts, and lo and behold, no skips under any and all conditions, quick, easy starting, this thing is back to kicking *** again.

I know a few folks run Bosch plugs with no problems whatsoever, but after spending two days chasing down driveability problems, I will wholeheartedly say (flame me if you must) that Bosch plugs are absolute junk for these engines. Want the best chance of your vehicle running at it's top? Steer clear or Autozone and those fishing lure Bosch plugs, and stick some Motorcrafts or Autolites in it. Your engine (and anyone who may be tasked to try to fix the weird problems that come with those junk plugs) will thank you.

We now return you to your regularly scheduled programming.

Quintin,

You really need to let you true inner feelings out.

Thanks for the heads up!

Hey, what took you so long???

Go ahead, tell us how you RRREEEAAALLLYYY feel! Sounds linke you're still holding back.

Steve

I can - I've tried Boch(Bosch) and Autolite and they both SUCK!! The Boch(Bosch) - I could get the motor to run , but just barly. The Autolites, my truck ran fine for 40 miles or so , then it started misfiring and tripped a light. Went back to Motorcrafts and all was well. I can do a plug change just under 2 hrs now on my 5.4L , lol, I guess something good came of all that.

As you may remember, I am chasing nearly the same condition but not quite a bad.
Only difference is my plugs are recent Motorcraft and ran fine for many thousnds of miles before the problem developed..
It could be that I have some kind if deposits on my plugs now.
Since my miss is intermittant and no codes it is hard to pin it on plugs or coils but there is always these surprises that can't be counted on until a substitution is made.
Thanks for shareing your experiences.

I can relate -kind of, after washing my motor last spring and knowing what could happen after I did - I took precautions and removed the battery before washing, before I reinstalled I blew out every connector with compressed air. I was asured and confident that I would escape from the COP drama.

After all that, I still compromised my COP system. I would get a code -fix that one , get another pointing to a misfiring cylinder and fix that one, then I just started getting the multiple misfire's code, ahhhhh.. Mannn, I tore that thing apart so many times, The coils always past every test. Well I think it was Quintin, who explained to me about the "coil under a load failure thing" - Long story short, I just replaced them all lol. That did it...

Been running GREAT!! , since..

The manager at our local Oreilly store said that Motorcraft makes Autolite, or vice versa.
Anyone know for sure?
I'm running Autolite platinums with no problem.

NOT!

You think there not causing you problems, I bet against it, your just satisfied with the way your vehicle runs.

They cost me money and time and totally cheesed me off. This isn't something I read, this is something I tried to use on my vehicle - these plugs do not work in my 98 5.4L.

Your running Granatelli Coil Connectors ? you mean Granatelli COPs? What-ever, if so , your generating a hell of allot more mega-jouls than stock COP's - overboard without a capacitor of some-kind. Whatever COP system your running they are all working harder than they should be just to compensate for plugs that restricts performance in these motors and don't belong there.

They install Motorcrafts in your vehicle from the factory for a real good reason.

Guess I shouldn't be rippen on you -apology.. I just remember the hell they put me thru on my first plug change.

It royally SUCKED!!!

Just new coil connectors....
Why do you think they're working so hard? You may have gotten some plugs out of a bad lot at the factory.
I have about 2,500 miles on them so far with no apparent problem.
As far as restricting performance........how can you verify that? Seriously...no sarcasm intended. I am curious.

use the pids to find misfires way before they set a code next time. once i learned that they are the easiest to get misfire counts. I beleive it is mode 5 on a generic tool. the motorcraft plug that the 4.2, 4.6, and 5.4 are manufactured by Autolite. Motorcraft does not manufacture there plugs as most parts. asked that question at the last dealer show. I have seen bosch plats in some no problem and others I swear did the same thing you talked about. I don't install them. different spark plugs makes and types are proven to make very little performance differance on O.E. engines most won't know the differance but if they think and it makes them feel better than that is better than power, and harmless to the rest of us

Well, to be objective, I admitt that you could be right. I really cannot speak for your motor or anyone else for that matter. Searched a little and most probs were with the Bosch plugs

Personaly, I don't trust them(autolites) after that and most likely never will again.

Motorcraft(failsafe)- NGK - Denso Iradium's.

OK I understand. I hope you've managed to get settled with what will work for you.
Why do you think these engines are so temperamental that they vary so on what will work in them?
So far so good for me. I guess only time will tell.
I had hoped a cooler plug would help performance, but I can't tell the difference. I say that, but I have managed to get an extra 0.5 mpg on the highway. That's really negligible, though.
Later

Autolite manufactures Motorcraft? Huh. That's confusing - Did Ford just market the Motorcraft name as diverse ? I wonder if anyone else had an Autolite problem other than me ? I have a new set of em on the shelf , next to the Bosch's lol
I think it's a mode 6 - cylinder history.

Thanx for your reply

See my reply #5.
After seeing what Quintin had gone thru and turned out to be plugs, I decided to break with thinking and put a new set of Motorcrafts in replacing the same that had about 15k on them.
You guessed it, no more missing.
Only thing I can attribute it to is the porcleans have become poisoned from some gas or additives in the past few months.
The plugs that came out have no obvious faults.
With the missing being not enough and intermittant for the PCM to set code or confusing the PCM as to what code could be set to indicate the fault.
Anyways it seems to show that this exoctic ignition system can still be 'tricked' by certain kinds faults.
I had been data streaming the engine and saw the IAT do sudden jumps.
Did one data stream after the plug change and no more jumps on the IAT trace.
No more misses at take off from a light or stop sign.
I had experience like this many years ago on a single cylinder Kart engine that would just die after a given number of track laps.
Took about 3 weeks to find it was the kind of crank case oil (KLOTZ) that was poisioing the plug porclean.
Thanks Quintin for doing the leg work on this problem.
At least you got paid for it.

I remember years ago switching from a Klotz(pre-mix) to Bel-Ray because of performance issues- couldn't tune it (raced motorcross) - was even running NGK's & hot U's and couldn't pinpoint the prob, that might of been close to the time your are refering to - switching to Bel-Ray fixed said problems, but maaann, did that stuff ever stink lol!!