engine problems

[bovine]

I have a 1993 Ford Explorer with the 4.0 that I have a problem with the rpm's gauge falling and cylinders cutting out when they drop. I have been trying to figure this out and for a few months now and the only thing I can think of is the ecu is crapping out but I wanted to check all other possible problem before I drop $100 on something and it doesn't help.

 

[arco777]

PCM failure is very rare. I doubt that is your problem.

I don't really understand the problem you're having, can you describe it better?

Also have you scanned for KOEO, CM, and KOER codes?

 

[buckwill]

it could be your getting a voltage drop insufficient to support ign and fuel injection, or your simply getting inj failure and resulting drop in rpm, that cud be inj signal loss,

 

[bovine]

when the rpm gauge is down at zero the engine run fine but when the rpm gauge decides to work the engine cuts down to 3 cylinders and spit and sputters but you can shut it off and crank it back up and it will run fine again.

 

[arco777]

Sometimes the tach itself goes bad. Fix is a junkyard unit, or in some cases there are bad solder joints that can be repaired. But since it correlates with your engine issue, I'd work backwards from the tach issue.

The tach gets its signal from the PCM. The PCM gets the ignition signal from the Ignition Control Module via the Ignition Diagnostic Monitor circuit (see diagram). I believe this module is located behind the left or right headlight and says something like EDIS-6 on it.

These failures lead me to believe there is either a wiring issue or failure of the Ignition Control Module itself. Failure of the Crank Position Sensor (CKP), located near the harmonic balancer, is another possibility.

 

[bovine]

Ok thanks i will try that since i have already changed the crankshaft position sensor.