NGK G-Power plugs causing poor mileage on a 4.6?

[MikeCA]

I replaced my plugs with NGK G-Powers along with a new fuel filter, new belt and new air filter.

My mileage has gone from about 14/15 in the city to 9-11. I've checked for a leak around the new fuel filter, nothing. The air filter is snug. I've since cleaned the MAF with MAF cleaner. The plugs were gapped to .054. I've got no CEL.

The idle is smooth, acceleration is great with no hiccups but now on the freeway doing 65 I'll get 18-19mpg whereas before I'd get 19-21 and the 9mpg in the city is just atrocious.

I'm leaning towards the plugs, but would they cause a decrease in mileage if they're listed as a suitable replacement?

Thanks in advance.

 

[MikeCA]

Just a friendly bump...

 

[drdoom]

Mike, did you do a PCM reset?

 

[MikeCA]

No, I guess I did not. Is there a specific process for this?

 

[drdoom]

Yes there is, I watched it on YouTube makuloco I believe is the guys name. I am a bit embarrassed to say I cannot correctly recall that simple procedure, but it involves disconnecting a battery cable and placing a jumper wire for about ten minutes... Sorry I can't help more, and honestly I don't know if it will even help, but it is a normal procedure for these trucks after doing maintenances.

 

[drdoom]

https://m.youtube.com/watch?v=hZAsoqmqhdM

 

[Number4]

I'd say pull the single platinums and put in an Iridium plug. I've had the Autolite XP104's in for a year or two now.

 

[MikeCA]

Thanks guys.

Iridiums over platinums? Does it make a difference in these hogs?

 

[anthonymtz]

I've got ngk in my lexus as a denso replacement, they are used more in imports, I would go back to the oem Motorcraft platinum's it rolled out the factory with, they are 4$ a piece at O'Reillys and my explorer's never ran better, I heard these engines get picky with "other" plugs, just like gm using AcDelco.

 

[anthonymtz]

Thanks guys.

Iridiums over platinums? Does it make a difference in these hogs?

The Motorcraft ones are your best bet, when I used bosch on the lexus it ran like 9mpgs as soon as I used the ngk plugs 16+

 

[Number4]

Iridiums are better than platinum. Platinums will most likely start to phase out. Well, they won't for sales reasons, but they should. Platinum is a poor conducter. Iridium has been around but only some what recently have they been able to use it in plugs.

Anything that takes platinum, put Iridiums in. Platinum was just the best technology at the time of production.
Anything that doesn't take platinum, put copper in.

Keep in mind, the Motorcrafts were the ones breaking off in the heads, so OE isn't a guarantee. Get the Autolite XP104's and you'll be good to go. I usually run Champions myself. In testing, they disipate heat better than Autolites.

 

[MikeCA]

I've reset the PCM now as per the instructions in the video.

Thanks again for the heads-up. I'll run tests and report once I have some numbers.