I'm throwing this up here, because even after reading dozens of misfire threads, and doing all the testing i can think of, i still can't diagnose this problem.

Vehicle: 1998 F150 supercab, M5 tranny, 4x4, 4.6 recently swapped out for a 5.4 (2000 manufacture date). Used PCM and ignition from the 4.6, so im still running coil packs.

History: Swapped 5.4 in, no major problems aside from some vacuum issues, and a late night diagnosing an alternator not charging. Had exhaust hooked back up recently, and while it was in had both cats removed, will have O2 sensors eliminated via tune when i purchase my programmer.

Problem: Cylinder 1 misfire, at first seemed to do it mostly under load when accelerating, but seems to be getting a bit worse.
I took the truck for a fairly long test drive (50km's or so), to try and get the computer to pick up as many codes as i could, seems to pick up the misfire better when i drop it into a high gear and let it lug till it pops up. the codes i pulled after getting back were:
P301-Cylinder 1 misfire
P1131-Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1(Ford specific)
P135-02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P174-System too lean (Bank 2)
Im assuming the 1131 and 135 are due to my removed cats, and possibly even the 174.
Short test drives only pop up the P301, occasionally a P174.

Corrective Actions:
-I switched the plug and plug wire from #1 with the #3-Still received P301.
(Applied some more dielectric grease just to be sure)
-Traded across the 2 coil packs to see if it was a bad pack- Still receive P301.
-Fuel pressure test-32 @ idle, 39 w/ vacuum removed, stays around 32 when revving, give or take. Seems acceptable to me.
-Removed injector from #1, placed injector from #2 in its place, replaced #2 with injector from the 4.6-Still receiving P301.
-Compression test on #1 (will do a full compression test when im off tour) pressure rises steadily and properly, ending @ 150 after 4-5 strokes, also seems acceptable to me.
-Apply dielectric to injector pins (im grasping @ straws here)-no change.

@This point i'm thinking possibly a bad ground on the injector? or even more remote some form of blockage in the fuel rail. Is it possible that the o2 sensors are making the engine run lean causing the misfire? The lean code i'm getting is bank2, that's the drivers side correct? So that doesn't make much sense. I was going to wait until my tune is complete to be rid of the rear o2's. but perhaps i should do a gottsmod or find some simulators right away. I should also mention that the plug wires i'm using are champion 5mm's, which i put in last summer, plugs are bosch plats that i gapped to spec, also last summer. I know people have had problems with the bosch's before, but if it worked in #2 i would think it would work in #1?

Thanks for any input that anyone can offer, and if there's any more info i should list, just let me know- Thanks!

 

You could have a roller follower off on the #1 exhaust valve. A compression test on only one cyl can be missleading, you need a comparison with other cyls. to get a better idea if your 150 reading in #1 is normal. Seems low to me but again that depends on the gauge, engine temp, etc. and other cyl numbers. A leakdown test would be better at finding a valvetrain problem such as a bent valve etc.

 

Update:
On a complete whim, I unplugged the MAF for the drive in to work, cleaned up the miss a ton, only was bad in 2nd on a long hard pull. That makes no sense to me. When its missing, it does it bad, only seems to be through a certain rpm range, and then it dissapears completely and accelerates hard. Honestly feels like another vehicle hit me and is launching me forward.

 

Update: Cleaned the MAF, has helped with the miss but not completely eliminated it. Still misses when im anywhere near WOT, almost feels like its leaning out as well. I purchased an X3 programmer today, im going to eliminate the rear o2's right away, hopefully get a full tune in soon. Any input?

 

A miss is a miss not sure what a tune is going to do for you. If it was me before I started buying all kinds of equipment I would eliminate any potential basic engine or ignition issues. But thats just me, carry on.

 

I needed to get a programmer to upload my tune to eliminate the o2's, and tune the PCM to the new engine. Seems like it is leaning out before it misses, so i think that may be one of the instigating factors. The fact that cleaning the MAF helped with the problem, and that unplugging the MAF helps as well, makes me think that perhaps the main problem is in the air/fuel? Thanks!

 

Makes sense sounds like you may have a handle on it. Good luck

 

diff plugs, diff wires.

 

That's what i kept thinking, but after switching the plugs and wires around, why would it keep missing with plugs and wires that were ok on the other cylinders? I ohm tested the wires and they checked out. If they weren't so damn new I wouldn't think twice about tossing them for sure!

 

Maybe cpu is wrong, I had one bad plug and cpu said "random misfire" Don't trust computer. You know it's missing, do what you did in the old days

 

Get those Champion wires and Bosch plugs out of there. Use Motorcraft plugs and wires. Check for vacuum leaks, especially the PCV elbow behind the intake manifold.

 

I bought a plug in tester for the wiring on the injectors. That wasn't the problem but it ruled out the wiring.

 

Update:
Rechecked all vacuums, checked out. Pulled all of the plugs and wires, ran a full compression test, all cylinders check out. Inspected all of the plugs and checked gap, all were good. I ohm tested all of the wires, and 3 running to the other bank tested unacceptably high, so i took them back in on warranty, exchanged them for NGK's. Took for a short test drive, still getting the P301 and P1131 codes, unplugged the MAF again, no miss whatsoever, just a slight bog. I'm thinking bad MAF possibly? That or the MAF isn't tuned properly for this engine. Ill see if the tune helps out, my tuner sent me a minor one with the o2's eliminated, etc, but sent it in the wrong format so i cant load it yet, i'm sure he can convert it for me monday.

 

It's rare that a faulty MAF makes the engine miss, especially a really faulty MAF or one that was disconnected as the PCM. This no longer uses the MAF and uses default settings, that's of course inefficient. -But, shouldn't make the engine miss either. More less shift different.

With tuning screwed with, - there's no telling lol.

 

It feels like it leaning out, i think maybe its something very minor only acting up when it gets super lean? I'm hoping that once i plug in the tune the eliminated o2's will help. I noticed my scanner also is capable of datalogging, so i think i might try that, and see if i can decipher something from that.