Well - I learned my lesson. While ordering a crankshaft position sensor for our car, I stumbled across some slick looking Bosch Platinum 2 spark plugs at a good price. Ordered and installed several weeks ago. I even had the part numbers down for the Motorcraft or Autolite plugs. Yes I am an idiot.

While I don't have any " serious " issues, the truck - 2000 Excursion with 100,000 miles - now doesn't run all so hot. The lack of or intermittent spark level is evident in the low to mid RPM range and fuel economy dropped as well. On the highway without load, the plugs seem to do fine and fuel economy is the same.

So today I'm ordering another set of plugs. My .02 to keep anyone else from making this painful mistake. Sucks to be me.

 

You're not alone. Most of us have done the same thing at least once in our lives.

 

yea its funny how fussy the mod. motors are to anything other then stock Ford plugs..

 

I'm currently running Autolite Platinums in my 10, so far so good. I was reluctant to stray from the Motocrafts, but my Allied parts guy hasn't failed me yet and was very confident in the Autolites.

 

I am VERY interested in hearing how it is after you put stock plugs back in it. DEFINITELY report back! This will go in the tech folder if you do

For whatever reason, these COPs are very picky. I don't know why. I can theorize why, but without direct hard evidence, it's only speculation.

A couple of years back, I read up on what "platinum" plugs were, "double platinum", etc. "Regular platinum" plugs have platinum in the center electrode. "Double" platinum plugs have it on both electrodes. Some have a wire running inside the center electrode, surrounded by standard copper I assume. Some are just tipped with platinum but the rest of the electrode is the same.

Copper's resistivity is 1.68×10^8 at 20C (that's ohms per meter).
Platinum is 1.06×10^7

Now, 10 to the (-8) is less than 10 to the (-7). So copper has almost 10 times the conductance of platinum, albeit it in such a short piece of metal, it's almost negligible. I have an idea that the difference in resistance is what makes the Ford COPs so unstable. But it behooves me to explain WHY.

Double plats would definitely be different than single plats, and if there is a platinum wire running all the way through the center electrode, versus just being tipped with platinum, that is definitely going to change things too...

Back in the day, about 20 years ago, I used to do a lot of work on Triumph TR7's for people around the East end of Long Island. Lots of people would see me driving, stop and ask me for advice about a mechanic, until I told them I did all my own work. Having been screwed by so many mechanics who didn't even know the cars, they would ask me if I would work on them.

Lots of idle and low-load running problems all came back to one thing. Someone had put Bosch plugs in them instead of the standard run-of-the-mill Champions that Triumph spec'd in the owner's manual. Put a set of Champions back in, they'd run like a top. No idea why, maybe the wrong heat range (which could also be a problem with using other manufacturers' spark plugs in our modulars). Dunno... I do know I had quite a collection of Bosch plugs in my garage after a while. Something like 10 different sets in as little as 2 years of shade-tree wrenching for other people. This is NOT a bash of Bosch. Just another example of how what seems to be a perfect match just isn't.

 

I changed the plugs in my Mark VIII to the copper core Autolites right after buying it with about 80,000 miles on it and ran them until about 170,000, last spring, and changed them just because they were due and for no other reason. They were burning a gray to a very light tan. I installed the Motorcrafts that were specified and within 2,000 miles I put the old copper cores back in because the performance dropped off so much with the OEM spec plugs. The idle was rough in comparison to the coppers but not too bad and the fuel economy got lower, as well as general performance = acceleration. Once changed back to the coppers all is well, everything returned to the performance I had become accustomed to. My Mark has coil packs and not the COPs so that might make a difference. When I replace the plugs in my Navigator I intend to use the copper Autolites and if it won't run the way I'm used to the OEM spec platinums will go in. As Krewat said, I think, the difference in the resistance may make the difference in the performance but I'm not smart enough to know why so I'll continue to use the coppers until my engine tells me not to.

 

Maybe a little off topic, but for what it's worth...
My previous mod-motor was a 4.6 in my 03 Mustang GT. I ran a Paxton Novi 1000 blower and CMS blower cams. With the boost heating the charge I ran NGK TR6 plugs and gapped them at .035. I know it's a different animal, but the heads are very similiar and it ran great with the copper NGK's. Funny thing was that a gap of .040 would create a loss in power on the dyno.
438 rwhp/408 rwtq.

 

With the wider gap you allow the coil to build a stronger charge and create a hotter spark when fired. A smaller gap will reduce the amount of energy supplied to the plug.

 

A spark plug fires as the magnetic field in the coil collapses, AFTER voltage has been removed from the input side of the coil.

Ignition coil - Wikipedia, the free encyclopedia

I can not find any information about it, but I'd say the bigger gap would NEED a higher voltage to arc across the gap. However, it's overall "strength" wouldn't necessarily be any stronger. It would help to ignite a lean mix because the arc is longer, but again, it's not necessarily any hotter.

 

Forced induction supplies an incoming rush of air that probably blew the sprak out somewhat with the larger gap.


I only ever put MC or Autolites in Fords, if it ain't broke don't fix it. Anything with a carb gets copper cores only.

 

Good point.

 

I just replaced the plugs in my 01 6.8L F250 and was planning to use the bosh, and my machanic, must be a little more crafty than I give him credit for, told me don't do it...
Well I'll be damn, he put in motorcraft, and it's running better than ever.

 

Motorcraft and Autolite are the best plugs for the money, i wont use nothing else, STAY away from Champion and Bosh plugs, i wont use those plugs in my Lawn mower if i dont have too, LOL