Hello all. Newby on this forum.
I'm dealing with a '89 Wrangler with the 4.2 and an auto trans. The rig has about 165,000 miles and I don't believe there has been any work done to the 4.2. The original BBD stepper carburetor has been replaced with a non-stepper BBD, but all else appears factory.
The owner has not been able to get the rig through emissions testing and has asked me to help. I am not overly familiar with the 4.2 and much of the information I have seen seems contradictory,
Ford Guy...I understand your frustration, the BBD carburetor and feedback system is complex, and the ECU/MCU and vacuum circuit interface with the distributor can be confusing as well.
There are two concerns here: A/F ratio of the fuel mixture burn at the emissions testing rpm and the ignition performance at these same speeds. Also, the engine has several emissions related components, including the Pulse-Air system, the cat, an EGR valve and vacuum circuit plus an O2 sensor.