1995 Aerostar starts then dies.

[HikerDave]

95 Aerostar has a problem no one can figure out. When the MAF is plugged in the engine will die. If unplugged engine struggles but runs, using the default setting in the ECM. You can drive it but will die when stopped unless you put it into neutral or park, ie. unload the engine.
If you plug in the MAF any airflow at all kills the engine.
Here's the obvious:
New MAF makes no difference
Housing is clean
It's not the fuel pump
ECM caps changed out
Don't ask about OBD1 KOEO codes: engine won't run long enough to get any readings with MAF plugged in and unplugged it just reports that the sensor is not working.
Connectors and wires are good

Everyone has given me their best educated guesses. I'm hoping to find someone who knows, who's actually run into this problem before.

Hiker Dave

 

[BrooklynBay]

How did you determine that the mass air flow sensor had to be unplugged to start it? You don't have to scan for codes while the engine is running. You probably have codes stored.

 

[HikerDave]

Starts but dies quickly. Started checking fuel system, air, etc. Checking the MAF revealed that behavior. My reader only shows that the MAF is not working/connected.

 

[BrooklynBay]

Clean the mass air flow sensor, idle speed control/air bypass valve, and the air charge temperature sensor. Check the condition of the spark plugs & cables.

 

[Josh P]

I'd see if it will stay running on starting fluid longer than what the fuel system does. You could pull the fuel pump relay to test. I have read your post entirely, and I'm surprised fixing the ecm didn't cure the issue. Does it run the same when it is a cold startup or warm?

 

[HikerDave]

Answering BrooklynBay:
The MAF is clean and as I stated I even swapped in a new one. It's not the problem. The plugs and wires may be OK: when running and loaded it scoots around fine, not missing, has power, no vibes etc. I do want to change them out though. (What a pain to get to anything. I swear they just took a Ranger poured a van body around it!) I will check the IAC and ACT, thanks.
Josh:
It starts and will run, MAF unplugged. At low RPM and loaded it will die. Even in Park or Neutral it will struggle. Fuel pump and relay were swapped out, no change.
Something I didn't mention concerning hot and cold running. When cold, like winter, it has hard time starting but runs ok (as good as it can with no MAF). A problem preceding all this by many months was that when hot, like summer and running hard for awhile it will really not want to start. It'll shutter and complain. One guy said it's akin to a vapor lock on a carbbed engine. He said that the fuel line is laying right on engine and when stopped the gas in there will vaporize and the engine will be starved intermittently. Sort of makes sense cuz if I force it to get rolling it will behave in a short distance. I'm thinking that as cooler fuel gets in the line the injectors are getting liquid and not vapor. But... Ive seen others on forums having that problem and adding recommended extra insulation to the line didn't help.

 

[BrooklynBay]

Will it start, and run with your foot pressing lightly on the throttle pedal? Did you check the engine coolant temperature sensor with an Ohmmeter to see if it's the correct resistance on a cold start?

Another test for the 4.0L is the CPS. Turn on the electrical system but don't start the engine. Put a ratchet on the engine pulley to rotate the engine a few degrees. You will hear the fuel pump prime with each small manual rotation.

Check the vacuum lines, pcv valve, brake booster check valve, and grommets for leaks & clogs.

 

[HikerDave]

Swapped out the IAC, no change. I can't even find the PCV location. I'll keep at it.

 

[BrooklynBay]

Follow the vacuum line to the pcv valve. There's an emissions sticker under the hood.

 

[don-ohio]

Check EGR valve too. They can really make an engine act up.