2014 F150 5.0L misfire

Hello everyone,

Got a complicated question. So I'm having an issue with my own vehicle and I haven't tried to solve it until now because it's still under warranty. I've gone to multiple dealerships multiple times and everytime I get the same answer... theres nothing wrong with it. I'm not on good terms with the local dealerships and I feel like they are a waste of time unless you have a CEL on. BTW no CEL in my case will light. Anyway There's definitely a misfire and it is very random. And it also occurs randomly on different cylinders. I did a power balance test and it occurs randomly across all the cylinders at Idle and more so at higher rpms. Mode 6 showed between 8-15 misfires per cylinder

The first PID I looked at was the ST fuel trims. At idle they were slightly positive at about 2 or 3. WOT it shot up to 15 and went back down. So fuel delivery or MAF. I have a 4 wire MAF like paul's video. Measured 14.4v at power, 2 low voltage at 50mV for the grounds, and there was a slightly higher voltage at the signal but I forgot what it was. Also voltage at that wire would change with the accelerator pedal so wiring does not seem to be an issue. Unfortunately there is no frequency function on the verus but there is on the autel but the sampling rate on the autel is horrendous and it does not really plot the frequency very well. That's where the Verus shines. The autel has horrible sampling.
So I tried going by grams/sec. The rule of thumb is usually the volume of the engine in L. So I observed the airflow and found at idle when under no load (not in gear) the gm/s was about 3.8gm/s with a steady rpm of about 630 and the STFT was about 2-3. More misfires would happen at idle under no load than if you were at idle and in gear.

So if you put it in gear, the rpm's drop to about 520 but the gm/s went up to about 4.2-4.5 and FT's would be pretty much at Stoic (maybe slightly rich) and would run smooth.That seems counterintuitive to me, wouldn't a drop in rpm mean less gm/s? Every once in a while the gm/s would dip regardless of rpm down to about 3.8 while in gear and that pretty well timed with when misfires would occur while in gear. This makes me suspect the MAF is skewed or is bouncing everywhere. What confuses me is, would we expect a rise in gm/s with a drop in rpm? The only other thing that increased was load, so does load play a role in gm/s as well as rpm? On top of that if I put the A/C on at idle rpms wouldnt change much but all of a sudden gm/s would shoot up to 6gm/s and misfiring would occure more. Only this time STFT would go negative.

This makes me think that at a higher rpm under no load, the MAF is under-reporting the airflow and going lean, and at lower idle rpm under load it is over reporting and going rich. I'm leaning towards a skewed MAF sensor but wonder if I can get input from others on what they think these results may mean and what if any relationship there is between rpm,load and gm/s. I'm also going to do a fuel pressure test tomorrow.

Thanks

I think I had a Duhhhh moment... throttle position can maybe also play a role? I'm going to hook up the scanner again tomorrow and check that out too

UPDATE: putting the vehicle in gear did not change the TP to any significant degree (maybe 0.1%) at all so the rpm drop was from the load.

Did a compression test today and all cylinders were 150 psi on the dot (wish I could do a runnning compression test Im leaning towards MAF because voltage was at battery voltage under load at the ignition as well as injector fuses and at each coil/injector, and the misfires are occuring throughout all the cylinders so its hard to think that all the injectors or coils would be bad. Fuel pressure is the only other variable that might be at play so ill check that also. I'm going to go ahead and order a new MAF from hitachi and let everyone know how it goes. I'm taking a chance but I'm highly doubting a bad fuel pump (I could be wrong lol )

I am curious if you got it solved? If not I am wondering in data stream where are your long and short term fuel trims? YOU SAY IT IS MISFIRING ON ALL CYLINDERS? I had one of these trucks with very low miles doing the same thing. Dealer told the customer nothing is wrong with the truck. In this case when I road tested it the misfire got worse under a load than at idle. I checked all the basics and came up dry. Ignition good. Injectors good. Compression good. I decided it had to either be in the cam timing. It wasn't. I decided to do a back pressure test and found a clogged converter. This was the fix. I am curious what you find.

Hmm interesting. In my case I ended up putting in a new maf sensor and did a misfire neutral profile correction and now it does not misfire when started cold but there still is a bit of a rough idle. I also found signs of exhaust in my coolant and the dealership claimed nothing wrong. When you say clogged converter do you mean the torque converter? Nm duuuh cat converter lol

Correct there was a random misfire in all cylinders.

I had slightly positive fuel trims at idle that would get more and more positive on snap throttle

I'm going to try a back pressure test on mine

JoesAutoElectric wrote: I am curious if you got it solved? If not I am wondering in data stream where are your long and short term fuel trims? YOU SAY IT IS MISFIRING ON ALL CYLINDERS? I had one of these trucks with very low miles doing the same thing. Dealer told the customer nothing is wrong with the truck. In this case when I road tested it the misfire got worse under a load than at idle. I checked all the basics and came up dry. Ignition good. Injectors good. Compression good. I decided it had to either be in the cam timing. It wasn't. I decided to do a back pressure test and found a clogged converter. This was the fix. I am curious what you find.

Also did you replace the cat? The dealerships here are a holes and will not do anything unless there's a light so theyll probably just claim nothing wrong again. Also same in mine everything tested good but the maf sensor had some odd readings at idle. I had a dead miss upon cold start also but that is now gone

No the dealer did. Truck had 5k on it or something like that.

JoesAutoElectric wrote: No the dealer did. Truck had 5k on it or something like that.

looks like I need to find another dealer here to look at it. I'm going to do a back pressure test on it and I'll let you know how it goes. And if it's high I'll take it elsewhere, luckily theres 6 ford dealers around me. I've taken it to 4 of them so far.... let's see if the 5th one solves it lmao. Thnx for the info

OK let me know man.

Will do. It might be a bit because its actually a good thing im going to check the back pressure because in another thread I am making a diy pressure transducer and I was watching how to diagnose back pressure using in cylinder pressure testing. Just waiting on some materials from ebay to arrive so i can complete it. Ill have stuff in my other thread as i make it and then ill show me doing the actual in cylinder test. Should be interesting

Hey everyone.... so i havent gotten all my materials for the pressure transducer yet but i made an interesting visual diacovery on my truck. Check out these pics.








If you look carefully you can see soot at the head gasket mating surface. Looks like a blown head gasket to me. It might be time to be an asshole to dealership

I have the same truck, with the same issue, and have been told its normal by 5 different dealers. One dealer drove it enough to get it to misfire on "Throttle tip in". They swapped the MAF and did an injector flow test before they called the hotline. Hotline said it is normal operation and to stop looking. I called to try and get a case opened, but was told the hotline has already established it normal and no case was needed. I fought back and forth that a misfiring engine is not normal, but never went anywhere.

Mine may be slightly different in that I do not get 8-15 on every cylinder, from normal driving anyway. I will have a cylinder or two that may have 0. I do have intermittent shuddering/hesitation/shift issues. After I drive home from work (45 minutes, 21 miles, 50/50 hwy/city), I can put the truck in park, hold it at 1500 RPM, truck will shake worse, and misfires on all cylinders will shoot up.

The exhaust restriction is intriguing, I will have that checked. By chance have you ever checked your crank sensor? My worst misfiring cylinders are 1, 2, and 5. 2 is last cylinder in firing order, 1 is first, 5 is second. Thought it was ironic, but have not had time to rip intake off to be able to reach crank sensor up by the firewall.