Zachatola

Im hoping you guys can help me out with this issue im i seem to be having. I am at about 33k on my truck, and i felt it was a good time to replace the spark plugs and regap them down to the .030 that everyone seems to feel is the best. I went with the motorcraft SP534 plug, and applied a small amount of anti-seize on the threads before putting them in.

I pulled each coil and plug separately so i didn't mix any up (not sure it matters) All the old plugs seemed to gap out about at .035 or so. I only ran into one issue and that was the coil in front of the HPFP when i lifted it up, it popped loose quickly and hit the bottom of the HPFP and broke the corner of the plastic that sits above the rubber seal. It doesnt look to have any effect on the coil itself from what i can see. I replaced all plugs and reinstalled all coils, and now im experiencing what i feel is poor MPG (~15-16mpg) when i was getting about 18-19. I have also noticed that my idle seems to be a bit rough, if i have my door open and i rest my hand on the door frame i can feel the truck running and shaking. I know there will be some movement the truck is running after all, but it feels rougher than i would expect.

The truck seems to have power, but i feel like im having to put my foot into it more than i use to with the old plugs. Im basing that on the "MPG" green bar meter that seems to ALWAYS be below my 17.9 marker even when im on flat ground, i feel like i have to literally barely touch the gas to keep it slightly above the 17.9 bar. I reset one of the trip odometers and ive only been able to baby it to 16.5 average mpg across a few hundred miles now.

Ive pulled the Mass air flow meters (3) and cleaned all of them with MAF cleaner along with disconnecting the battery to hopefully allow the truck t relearn the new MAF clean values, but im at a bit of a loss why i LOST mpg after changing to new plugs. Did i do something wrong, should i go back to my old plugs ( i still have them), could it be winter gas im seeing?

Any help you guys might have would be very welcome.

Bravo3eco

Did you torque the plugs down? They are sensitive any amount of over torquing them will crack the porcelain and causes what you have.
Did you change boots? Those are $2 ea and usually done with the plugs

Zachatola

I just hand torqued them down. Nothing wild, but i didnt use a torque wrench. Will i be able to see the porcelain cracks if i pull them and check them?

I didnot do the tips of the coils, this is my first motor like this, so i didnt have them. do they go bad over time?

DaEnforcer

Can you post a picture of the plugs if you are still having issues?

chimmike

a closer spark plug gap does nothing to promote a full burn; the idea behind closing the gap on forced induction vehicles is to prevent 'blowout' of the spark. Opening the gap to recommended setting in the manual promotes a fuller burn of the fuel, which would explain poorer mileage (unburnt fuel leaving cylinder/out turbos and exhaust) from less power, requiring more work to move the truck.

EDIT: OK, OP's post is 5 months old. My post is basically worthless to that, lol.