1994 4.0 Running out of options... SOMEONE PLEASE HELP

[itty.bitty.ali]

So, my mom has a 1994 4.0 Ranger that was handed down from my grandpa.

Initially, it was having problems with the ABS light coming on and felt like brakes were completely shot... so that got fixed and then...

ALL HELL BROKE LOOSE....

HERE ARE THE PROBLEMS...

Engine runs PERFECT when it's cool and driving straight shots, no red lights, no stop and go.

When then engine warms up, you come to a stop, or are just sitting in one spot for anything longer than 45 seconds, you get:

• loss of power
• hesitation
• wants to die
• irratic idle
• misfire

here is everything that has been changed.

• Spark plugs and wires
• MAF
• O2 sensor
• fuel filter
• coolant sensor
• temperature sensor
• throttle position sensor
• just about every sensor EXCEPT the idle control (why is beyond me)
  
  Noticed when my mom would run the AC that it hella screwed up, so we disconnected the A/C compressor. It also ran better w/ the MAF sensor disconnected so she left it that way (bad i know but she's stubborn)
  
  When scanned it got every sensor code that we replaced and even said at one time, that it couldn't make contact with vehicle.
  
  I have been driving this PITA lately and am honestly tired of stalling in intersections, and dying out on me at lights...
  
  ANY SUGGESTIONS...
  
  last thing I could think of is ECM?

 

[RonD]

Computer has two basic modes of operation.
Open Loop
Closed Loop

In Open Loop the computer operates the engine from Factory data, basically no O2 sensors feed back.
Open loop is used when engine is cold, the temp also sets a Choke routine, high idle, advanced spark and Rich fuel mix.
Open loop is also used when MAF sensor or O2 sensor data is not available(unplugged or similar) or is suspect.

Computer switches to Closed Loop after about 5 minutes of engine warm up.
Computer then relies exclusively on MAF sensor to determine the volume of air coming in, it uses that to calculate the 14:1 air:fuel ratio.
After that mix is burned in the cylinder, computer watches O2 sensor data from the exhaust for that burn, if there is too much oxygen then burn was lean, too little oxygen and the burn was Rich.
Computer then fine tunes the original calculated ratio, this is the Fuel Trim that gives the best MPG.
When engine is warm and idling computer switches to Open Loop again, idle must be rich so computer ignores O2 sensors when idling.

Yes, it is a shame about replacing all those sensors, they say 90% of DIY replaced sensors were not bad.
And 10% of new sensors don't work out of the box........so.....lol, you just add another problem when swapping out sensors.

All sensors or controls can be tested with volt/ohm meter, so $25 meter will save $100's in bad swap outs.

IAC(idle air control) valve is used by the computer to set high idle(1,100) when cold, and then warm idle (650)
Does the engine idle high when cold?
Does idle bump up when A/C is turned on?

After engine is warmed up, let it idle and then unplug the IAC valve's wires, idle should quickly drop to 500, or engine may stall, either is good.
If idle stays the same and then slowly dies, replace IAC Valve.

Spark is not part of the computer on a '94, it uses an EDIS-6 module, computer does send this module spark advance info for better performance, but EDIS-6 does just fine without it.

Could it be the PCM(ECM)? sure, it could, if it doesn't "talk back" to scanner then maybe.
PCMs don't fail that often, but it isn't unheard of either.
Generally if you pull it out and open the top cover you will see damage in the circuit board.
This is what it should look like inside: http://www.auto-diagnostics.info/ford_eec_iv

 

[93 4x4]

Yes go to the computer open it up and look for broken connectors on the diodes or black dots underneath The diodes on the circuit board, they have a tendency when they get old to leak

 

[holyford86]

reading your issues it seems like its a ground related problem, it will cause all sorts of strange stuff. Also, diodes don't leak, capacitors do.