HardDrive

So are you saying it Idles better now? My truck Idles bad also Thinking of checking my plugs to.

brucesears

I checked my plugs last week, all were .040 or greater. Haven't had any issues but idle did smooth out after narrowing the gaps to .034. Tried out the SCT 91 tune(thats premium in this area) and could hardly believe the difference between it and the 87 tune. Pulls much harder from a stop than before. Easily spins the tires with tc off and second gear rubber more than before.

boost2012

Last 1000 miles the idle was better, dont know why, same gas from same place.... . Anyway did the spark plug gap and the idle is the same as was last 1k. what's interesting, I have IDS/VCM and had a single misfire in 20 min test on cyl#4 where one of the plug was 0.36. I'll do the same test this week to see if it has change. Truck has now 11K

mhamershock

I was a bit skeptical about a plug change making that big a difference. I should know better what with having 15 or so different gas engines around the house: 2 strokes, 4 strokes, from a 1949 TO20 to my 2011 F150. Lord knows I change enuff damn spark plugs.

So I swapped out to one-range colder Autolites gapped at .032 or so and it's definitely better. I'm getting slightly better mileage (5* 87 P/T tune), and the truck runs smoother. I'm towing 9000 lbs to Glen Helen (9 hours) in a week or so and that'll be a real test for it.

The change is moderately easy to do as posted by others. Not as easy as my old Torino straight 6, but better than my 91 SHO. Still need to be a bit limber to climb up into the engine bay to get to the rear plugs. Fortunately I had my 6 year old boy helping me and that made it go SO much quicker.

Heishman

^^^^^^
I sure could have used a "6 year old's arm" when I dropped a socket into the black hole. I even listened hoping it would hit the concrete, but the black hole was to powerful

boosted150

Here's what I've found so far about the differences between plugs people are using.

NGK-LTR7IX-11 Reach: 25mm (.984")

NGK-LFR7AIX Reach: 26.5mm (1.04")

Autolite XP5364 Reach: 17.98mm (0.708")

These are vastly different from each other.

Judging from the lack of posts saying, "I ruined my pistons," I'm guessing hasn't caused any problems yet.


Does anyone know the stock plug reach? The Ford Parts website just lists overall dimensions for the plug (3.63 IN x 1.00 IN x 1.00 IN), and I'd hate to go pull a plug just to measure it.

VoiceOfReason

LTR_IX is the correct plug series. LFR_AIX has a crush gasket which is why the reach is extended in the specs. The final position of the electrodes will still be in the correct spot inside the head but this plug type is not recommended by Ford.

The number 6 or 7 refer to the heat range. 7 is colder than 6 for NGK plugs.

HogFan

Pulled mine and closed the gap to .034 on all. All were above .040 and one on the left bank was .046. I have not had any surging, but have had rough idle. I have now driven a week or so and I can tell a big difference in my idle (much smoother) and also with the throttle response (especially at mid ranges). Truck seems to make power quicker with less to no lag and is more spirited. I have also seen a bit better fuel mileage. My truck had started at 17.5 MPG with mixed driving when it was new and with just over $15K on the clock, it was getting about 14.5 MPG mixed. Following the gapping exercise, it is now back to near 18 in mixed driving. I am glad I took the time to do this, satisfied that it has made a difference. Love this forum !!

boosted150

I just got my NGK-LTR7IX-11 in. *CAREFULLY* regapped them all to 0.32, and the tips are all still intact, thank god. I'll install them this week and post what I find.

focus289

Pulled my plugs today all were between .037 and .040. Re-gapped them down to .030 and the truck seems to run better. I am running Livernois 93 v2 tune.