Well after dealing with the nightmares of rebuilding the turbo Frontier's motor, tuning the ole' 79 chebby, and then having someone blow up the diesel; I am here for my 2012 F-150 Lariat 2WD with the 5.0 and 3.55 rear gears

THE MAINTENANCE:
Truck has 92k on the clock and I decided since I didn't know the full history of the truck and was getting rather poor mileage (12 in town maybe 16-17 highway) it was time for a tune up.

I replaced the plugs with motorcraft iridiums (same as the ones that came out), the old ones had gaps of about 0.060"-0.065". I gapped the news ones with feeler gauges to 0.050 +/- half a thousandth. I did break a couple of the coil clips by not paying attention when I was removing them from the coils, however, they snapped back onto the coils without issue it seems.

I replaced air filter with a new Motorcraft one. The old one was absolutely filthy.

Cleaned the MAF while I was in there with MAF cleaner. It honestly looked pretty clean but figured might as well.

THE PROBLEM:
Re-hooked the battery up, unfortunately got a nice spark show when I dropped my wrench on it, fuses seem fine though. Started her up to idle and shifted through the gears. Took her out for a little drive and boy does she have a good deal more pickup now. Yee-haw! However, later on when I get back in the truck and start driving I all of a sudden feel the truck pull against the brakes. I look at the tach and the needle is dipping down the 400 and then back up to 800 before settling to about 550 and then dipping again. Rinse and repeat.

So, having dealt with idle ghosts before on my last 5.4 3v, I turned off the a/c to see if it had any effect: little to no changes in the surge. I unplugged battery again and came back 20 minutes later to try again. Start her up and let her figure things out. Idle seems fine, has maybe a 50-100 rpm bounce, which is more than it had before the tune up. Tap the throttle once and the surging begins goes from 50-100 rpms bounce back to the more drastic surge.

She drives great otherwise except at idle. She is eager to try and break loose the tires and show off that god awful 4 chirp wheel hop.

OTHER MISCELLANEOUS:
I have hooked up my obd2 scanner through the torque pro app. No codes, no faults, good AFRs. Everything seems within parameters, however, a little quirk I noticed is that I can only see the 2nd O2 sensors in bank 1 and 2. no sensor 1s. The 2nd sensors are reading flat voltages on the graph, although if they are rear sensors I believe that is correct.

 

.050 seems on the high side, Shouldn't they be closer to .040? I'm sure Patrick and a couple other 5.0 owners will be around soon. I know with the EB Ford recommends .030 and some are running .025 to .028.

Yes i know with a EB it has to have smaller gaps from being Turbo charged, just that .050 seems high.

Also with 92k on the odometer it may be a good idea to replace the boots also. They are only a few bucks at the ford dealership

 

Well owners manual called for a gap of .049-.053 so I settled for .050 to allow a little more wear life before they get regapped. And the boots didn't seem to be in bad shape but it probably would be a good idea to change them. Just don't get what's with the sudden idle surging. Ran so smooth beforehand

 

I have read where there is some question about gapping the plugs that wide and some have gone back and gapped 43 to 45 and it smoothed out the idle. Something else that can cause idle problems is the MAF. Did you clean the MAF with a cleaner specifically for cleaning electronics/ Spray it on and let it drip dry?

If it was the boots or coils, I would think it would miss under a load, not what you are experiencing.

 

You I used a MAF specific cleaner when cleaning, crc if I recall, and took precautions to be gentle. If it were too much gap then why did it run smoother with varying gaps over .060? Just got in her again. In park it's not as bad but it's definitely still bouncing more than usual. In drive though it will surge and fight the brakes.

 

If you change out the boots maybe consider taking the gap down more.

 

Another thing you may try is doing a hard reset of the KAM.

There are a couple different ways to do it.

1st way is to unhook both terminals from battery and touch them together which will erase the memory.

2nd way Is Disconnect the negative terminal only and run a alligator clip jumper wire from the positive to the disconnected negitive and let it sit for 5 to 10 minutes.

With both of these ways you know 100 percent that the memory has been erased.

 

I did try the second method of the KAM reset. And that owners manual is before 2012 I think. Mine says 0.049-0.053 I'm not sure why it changed since the motors didn't change any.

 

Probably to squeak out another .1 mpg

 

Clean the Throttle body

 

Can't believe we had not already called that one. Needs to be done even if it is not the cause of the surging, but very well could be.

 

Pretty common for surging. Basically the throttle can't find perfect idle spot because of the film of oil and junk on it impedes air flow. So the throttle goes back and forth trying to find idle. Closes too far (plus film) and it chokes engine, so then it opens it more to allow air, and you get surge effect over and over

 

Engineering doesn't program for "wear and tear" so they don't have a program for higher mileage vehicles to help relearn idle... it goes to baseline where it's programmed as idle but the film impedes airflow and causes surging

 

I love how I never seem to get email notifications that people have responded. (Or I do and I forget, ha either or)

Yeah I haven't really touched or looked at the throttle body funnily enough, even though I have always been meticulous with them, especially on my ole' 5.4 3v (RIP)

It seems like a fairly good spitball idea but of course I am going to try and rationalize it before I start tearing into her again. Before tune up I did a KAM reset due to poor mileage 11.5 in town 15 highway AT BEST. Things didn't improve much except for throttle snappiness and the god awful shift strategy which went from dreadful to ever so slightly less dreadful.

With maintenance (plugs being new and gapped down to .050 instead of varying gaps over .060 plus new air filter; oh and i went and bought a new motorcraft MAF since I reckoned maybe cleaning the sensor on a 90 degree day with a can of cleaner direct from inside a 70 degree house may have caused a micro-crack in the element. Didn't help, also did another KAM reset. On torque pro over my last ten driving trips I have had: about 100 miles total
2 misses on #1
1 on #2
5 on #3
and 2 on #5
0 on the rest

Doesn't seem too bad and it may have been holding a log from before the tune up. the amount of missing is not nearly enough for the constant surging of 450 to 700 rpms that is jerky enough to pull against the brakes at a light.

That does leave me considering that throttle body could indeed be an issue. Can this throttle body be cleaned fully off the truck and allow you to operate the butterfly while cleaning or do you have to be uber careful to not allow anything to move whatsoever like the 04s?

Still leaves me wondering why it didn't do this until after a tuneup even though I did a KAM reset shortly before the tuneup.

Guess I won't be able to tell until I yank the throttle and see whats going on right!