ECU Bypass and CEL 5/8 Question?

Fascinating issue. I believe the earlier Bosch units did not have O2 sensors; mixtures were simply adjusted with a simple hex screw located within the distribution unit. As time went by the margins of O2 error became legislatively more narrow.

I remember my aftermarket suppercharger [5.0 Lincoln] would command a sudden rich condition at boost which took some time for the O2 sensor to stabilize. (That was Speed Density). The emision control device to eliminate this was to put a wooden block under the accelerator peddle so the test technician could not activate much boost.

In normal driving the rich condition never was seen long enough to smell sulphur but the Check Engine {rich condition} would flash on and off. A short length of black electricians tape over the light was sufficient.

My Mondi 3.2 does see rich condition from time to time and the light comes on then goes off. Never any sulphur smell. The light is where I never see it to begin with. And of course I do not have emissions checks out here in my rural area. But here is the thing!

I actually removed the cats from my 1984 Z-28 and still passed emissions by simply splicing a plumbing T valve into the PCV line. Just introcuce some sucking sound air to the intake and bingo. Full compliance.

It is not clear to me how many US States require a full exhaust sniffer test on older cars. My rural county in Georgia does not require any tests on any cars. Further, it is my understanding many jurisdictions simpy require a visual that nothing has been removed, and do not require an actual sniffer test on older cars.

This all seems like common sense to me. We call it 'The Grandfather Clause'. Specifcally, it is not worth the grief and cost to police up the few aborant vehicles mostly poor people use to get about.

 

I have the same weird setup on my T. Someone installed aftermarket cats and some of the sensors are unplugged and I have those weird buttons as well.

If you figure out anything more on this setup let me know. I'm getting ready to pull the cats anyway and install test pipes.

 

The weird buttons are for retrieving the stored ECU fault codes. Check my348.com for instructions on how they work. The green faced box on the left of your photo is the cat temp ecu. They can be disconnected but the main ECUs will not know how hot the cats are and therefore won't illuminate a slow down light in the event of an overheat. A few owners have installed aircraft style Exhaust Gas Temperature gages to monitor cat temps., a cheaper option than replacing the cat ECUs. The green face on yours indicates a replacement. Originals were black.

Dave

 

I had 3 issues.
The first time it was a dirty MAF sensor plug contact on the right bank.
Deoxit-5 to the rescue. Cleaned the contacts, wiped off the excess. Fixed.
The second time I had a cooked thermo sensor that is screwed into the Cat. That was replaced and all was well.
The third time I got a slow down light which then went to a stop engine light. It was the little green ECU. They are real crap parts. Any dampness or moisture that creeps into the ECU between the plastic shell and the epoxy will cause havoc.
If you take the ECU out and put it in the hot sun for a few hours with a couple of small screw drivers separating the plastic shell from the epoxy, the moisture will evaporate out. Then re-glue the shell to the epoxy encapsulate with silicone bathroom caulk, the good stuff that lasts 50 years. That should seal it up forever. Hopefully no more moisture will get in to that thing.
I got tired of this crap and had the innards of the cats removed. So now there is no way I can get an over-heat condition, there is nothing to overheat.
The car runs the best it ever has.

DavidJ