i don't know [or at least remember reading about it in this thread] if it was asked if the throttle body may have some deposits behind the blade ?
this just popped into my head, so sorry if it has been talked about before, or this does not apply to your setup.

Bob, we haven't done anything with the throttle body yet. Should I just pull the air box off and flip the blades up and check for buildup? Is there anything in particular that I'm looking for? Will do this first thing tomorrow, sir, so please advise on how you'd approach this.

usually, you can see a darkish deposit when you crack open the blade, instead of the clean aluminum and shiny blade surface when the blade is shut.
there are sprays made to clean these deposits with the throttle body connected, but any that i have cleaned, i remove the throttle body and clean it on the bench. that leaves the intake much easier to thoroughly clean.
i have used different things to clean with, including lacquer thinner, mineral spirits, and spray carb cleaner on a rag.
just make sure you remove any left over chemical residue [if any] so it doesn't affect any down stream item like an O2 sensor. odds of that happening after combustion is almost nil, but you never know........
this may make a difference, it may not. i have cleaned up throttle bodies that i was sure it would make a difference because of all the crud behind the blade, and it did nothing. i have also cleaned some that looked almost new, and saw a dramatic difference, so this was just something that popped into my old, foggy brain, so i thought it can't hurt.
and to others out there, what really causes these deposits to form behind the throttle blade itself, and on the intake ? there can't be THAT much reversion traveling up the intake, can there ?

I appreciate your advice, sir. There is indeed crud behind the blades, and I will be pulling off this throttle body to clean it at some point. I'm out of time before school starts again, but thank you for pointing this out, sir.

I replaced the speed sensor on the differential. I now get a steady reading, instead of an erratic one. However, it now reads 15 mph when I'm doing 60, and between 5 and 10 at around town speeds. OD and TC lockup engaged today, just fine, though. Maybe it helped, and my speedometer isn't reading correctly because of another issue.

Miss continued as normal.

There should be two speed outputs on your vehicle.

The RWAL sensor on the axle is for the speedo.

If memory serves me, the unit on the trans is needed and used by the SBEC/Powertrain Controller.
Without a DRB or equivalent I don’t think you can “see” the sensor on the transmission and it’s output.
I believe you can check to see if it is working by using a DVOM while spinning the output shaft. It reads off the overdrive park lugs using a Hall effect sensor I believe.

Transman, there doesn't seem to be a speed sensor on the 4x4 A518 in my truck. The 2wd A518s have it, definitely. I will search more in depth on my vehicle, specifically.

MISS SOLVED.

There was this grey vacuum line running behind my throttle body. It was broken in such a way that you couldn't see it unless you were kneeling on the bumper. When I fixed this line, the miss went away. I am not certain what this line is specifically for, but it ties into a whole bunch of other vacuum lines. I drove the truck hard, and there was no miss, at all.

Been a while for me. Check on the transfer case.

There should be a sensor on the transfer case extension housing if I remember correctly. It would be nice if you could see real time data from the PCM. Is the odometer erratic and reading lower like the speedometer's speed is doing?

that is GREAT to hear ! i knew you could do it !

HA! Jokes on me.

Truck is now backfiring and jerking while driving.

We're back to square one, gentleman.

The odometer only works when the speedometer is engaging. With the old speed sensor installed it was erratic. With the new speed sensor installed, it works, but reads more slowly because it thinks I'm driving everywhere at 10 to 15 mph.

,

On some vehicles you need to program pinion factor which takes in to account tire size and gear ratio.
Not sure I found that applies to your vehicle. That programming feature may be available on the code readers at the auto supply.
Your larger independent repair shops have the electronic tools to do that.

Thanks for your help, Transman.

Unless a solution comes up for this backfire, this truck is getting retired. I can't afford to miss any more school and he is no longer reliable enough to count on. I'm at a complete loss. Love this truck, can't keep throwing money at him. I've got 12 more months in this trade program, and if I lose much more school I'll lose my scholarship.

I do not think you can program the earlier pcm's. Go back to the basics. When did the miss start? Is it a miss or a lean condition? What codes are returning?

well THAT sucks !
you now need this :

It could very well be a lean condition caused by a failing fuel pump. Highest fuel pressure that I read was 35 psi, after bleeding gauge. I don't know why I had to bleed the gauge and spray fuel everywhere to get the thing to read even that high. Fuel pressure fell to 30 psi while driving, but stayed there. I've read that fuel pumps can fail slowly, and not just quickly. Fuel pump whines loudly, engine surges for a few minutes at every cold startup, for about a minute. Is now doing the same surging, followed by a backfire. Not a loud backfire, but is still there.

Replaced list.
1. Plugs
2. Wires
3. Distributor
4. Coil
5. Crankshaft Position Sensor
6. 02 Sensor
7. Speed Sensor on Rear Differential
8. PCV Valve

You need to find out what the fuel pressure should be. Do you have the FSM to look it up. I am guessing here but I believe the pressure should be 50 psi.

I've tried two different gauges, have driven with both of them attached. Both required bleeding before registering fuel pressure, and both showed the same readings. Both gave me 35 on startup (after bleeding the gauges and spraying fuel everywhere), and then both fell to 30 while driving. Fuel pressure would slowly fall after truck was shut off.


FSM says 35-45 psi.

I have never bleed a fuel or oil pressure gauge. If the fsm says 49 psi than either it is the pump or your gauge. You need correct fuel pressure or it will not run right period.

I was wrong about 49 psi.

FSM says 35-45 psi.