Hello! I have a 1999 ford ranger with a problem. The problem is it only runs with the maf unplugged "maf is new" and random shuts down almost like the key is turned off. I suspect a pcm but idk any insite would be appreciated

 

Welcome to the forum

Is the "new" MAF a Ford part or 3rd party
Many "new" 3rd party parts are bad out of the box, the OEM(Ford) parts are tested, which is why they cost more, lol.
Nothing wrong with saving money, I do, but I also have taken parts back that were bad out of the box.

Any way unplugging the MAF puts computer into Open/Safe Mode, so it is running pre-set air/fuel mixes and basic spark timing.

So having engine run better with MAF unplugged could mean another sensor is failing.

You need to read the codes in the computer, you will for sure have a MAF code because it has been unplugged, but there should be other codes as well
WRITE THEM DOWN!!!!!!!!!
Do no buy anything

Post them here

Your current description is to vague without codes
Could be fuel pump/pressure
Could be TPS(throttle position sensor)
Could be a loose wire

PCMs rarely fail, not never, but rarely, so long shot
If there are no codes and/or the CEL(check engine light) isn't coming on than could be PCM problem

 

The maf is 3rd party but here's the thing the truck does not start with it plugged in. The only codes are that the maf is unplugged.

 

Yes, that is not uncommon but the reasons for it are not specific

How does the truck drive with MAF unplugged?

Was anything changed recently?

What made you unplug the MAF sensor the first time?
What symptoms leading up to unplugging it?

Do you have a volt meter to test MAF sensor voltages?
Could just be a bad MAF wire

1999 MAF sensor has 6 wires, 2 outside wires on each side are for air temp, IAT
MAF gets 12volts with key on to heat up a wire inside sensor, also a Ground for that 12volts, 2 wires
Last 2 wires are the sensor itself, one will have 5volts, from computer, this 5volt wire is split/spliced many times, and also powers TPS and IAT
Other sensor wire is Return voltage, should be .5volt engine off, key on, and about 1-1.5 volt engine idling(1,000rpm), 3.4-4volts at 5,000RPM

If you have a short on Return wire and it has 5 volts then computer will flood engine, or bad connection and 0volts then no fuel

 

i unplugged it becuase after doing the head gasket and heads after they cracked and got new injectors I went to start it and it wouldn't start. It was after that I thought to unplug the mass airflow sensor. I think it is the pcm becuase the night we got it running we heard a noise like a light bulb going out and it now does not start unless the maf is unplugged but even then it will die when starting it up starting then turning off or just driving along and it dying.

 

So engine was overheated and a head cracked, OK, making a little more sense.

So upper engine wiring harness was moved out of the way, then all sensors and injectors plugged back in.

Did you plug in the Crank sensor, on crank pulley, front of the engine.
Cam sensor, top rear of engine
Check for tight connections

You can pull out the PCM and remove it's top, warranty is over, lol, have a look at the circuit board, if what you described happened in the PCM you would see the blackened area of the short(pop noise)

So engine started and ran OK until the "pop"

I assume you pulled out each fuse in the engine fuse box to give it a look?

 

It was running ruff when I got it started again. All sensors are hooked up but still it runs bad. Idk what's wrong with the pos

 

Well me either, not there :)

Computer is not really a computer the way we think of computers now, it is just a calculator, so if the wrong numbers come in(sensors) then the wrong results come out, rough running.
Old computer programmers saying applies, "Garbage in = Garbage out", it just means computer doesn't make the mistakes, programmers do

Calculators rarely fail but not never, I would have a look inside just to take it off the table.

Also since spark plug wires were removed.
very very common mistake which I STILL make on the Ford V6 coil packs
Spark plug wiring on coil pack
3 4
2 6
1 5
front

OR
1 5
2 6
3 4
front

The 1 2 3 side I get right every time
The 5 6 4 side I get wrong, even after double and triple checks, I KNOW IT IS RGHT!!!, and it isn't, lol.
These are "matched pairs" 1/5, 2/6 and 3/4 so have to be next to each other

I even reversed 5 and 6 wires AT the spark plugs once

And this does cause rough running, lol

So double check, follow each wire to its spark plug, simple to do to take it off the table

 

I'll do this again but I'm sure the firing order is right

 

Yes, me too, and every time it was wrong I KNEW it was right

 

Im going to have to take it to a shop becuase it has been burning gas