Re: engine wirring
My understanding is that you are all sort of right...
The engines computer (ECU) is mounted under the dash inside the Jeep behind the clovw box.
The Ignition control module (ICM) is mounted under the washer bottle on the drivers side engine compartment.
The ICM takes cues from the ECU to control the spark.
That's for the 4.2. I can only assume it's similar for the 4.0. Either way the actual computer ECU should be under the dash.
'88 Sahara, 4.2, auto.