Hello all... this is my first post as i just bought a 1981 c3 with what i was told are original 1969 side pipes on the car. The pipes sound great and the pipes are fully functional. I have a check engine light that comes and goes. The previous owner had the check engine light checked out and his mechanic said its bc of the side pipes and they are missing some sensor. He stated if i went back to stock exhaust the check engine light would go out and stay off... i love the side exhaust and do not want to go back to stock ehaust... Anyone know how to get the check engine light off and keep the side pipes installed and fully functional? Thanks in advance to everyone for their help.

 

YOU ARE MISSING THE OXYGEN SENSOR FOR THE CATALYTIC CONVERTOR.

So there are two things missing the oxs sensor and the cat.
The ECM is looking for oxs data.

Coff.coff

 

Beyond my pay grade. But before I start removing exhaust systems etc. I would assume you check and hook it up and get the codes to verify what it’s looking for.

Can you not add O2 sensors to the exhaust?
Would they be I the correct range to satisfy the computer ? Ike

 

Thanks for the help.

Is there any possible way to install one and get it to talk to the ecm to remove the check engine light?

 

While it may be possible to add the oxs via a welded in bung on the pass side (same a the warm up manifold flapper....I would look up the correct part number for an 81
and go from there.

The oxs in my 82 is in the central 2-into one exhaust pipe just before the CAT. So it is reading both banks....not just one.

Good luck.

Unkahal.

when you get this really squared away I'll bet it runs better. I am presuming that the Varijet carb is long gone????

 

I believe the original carb and distributor are still on the car but not 100 percent sure i can check tomorrow. The car is a 42000 mile survior with nothing touched other than the side exhaust from what i was told. It was babied its whole life.

 

Take it to a shop and have them weld a fitting to the exhaust. Not too far downstream. It has to reach high enough temp

 

Cut the ground wire going from the ECM to the light and motor on

 

Or, have an aftermarket CAT installed and a bung for an oxygen sensor and get it back operating as intended.

 

That's what I would do. Or just pull the bulb out.

No way I'd put the stock exhaust back on, or a cat.

 

No need to! They make an o2 sensor sensor cancelor that solders to the 4 wire o2 sensor original harness conector that is probably hangining near you left side ,driver side exhaust manifold. I will send you the product name and where to purchase one tomorrow if needed. Once attached it will always send a proper volt signal to the ECM no matter what is coming out of the manifold as far as oxygen levels in your exhaust...

 

I’m in the process of updating mine also,and installing long tube headers,so would love the information on a alternate route with the sensor thanks.

 

Me too! I could use this info, I'm planning to put side pipes on this summer. Thanks!

 

you either use the E4ME setup correctly or you remove it. the O2 sensor tells the ecm whether to ricjen or lean the part-throttle (gas mileage) fuel mixture. you do not need a cat. the cat is after the O2 sensor. it is not like the P0420 codes on modern cars which are grading the exhaust AFTER the cat to check converter function for emissions inspectors.

 

Derek brings up a good point. In my limited knowledge of these systems, I thought the O2 sensor only helps it run smoother and more efficiently. There is no good reason to jump it out. They are cheap and easy to change when worn. The cat? Eh…ditch that bitch. Who cares. But the O2? Put it back.
please correct my logic, if wrong.

 

it is a primitive system but still works. the ecm sees the oxy signal and either leaves the main metering rods up for richer or down for leaner for a longer time. a solenoid cycles them up and down. if the ecm sees ideal mixture it will most likely stay at lean. this system regulates fuel at idle and at light load cruise speed. which is where our cars spend most of their lives. and if it is leaned out at light throttle at 55 mph, the lack of gasoline to burn may make the engine start burning aluminum piston tops instead. what i would do with a CCC setup is jump the pins and read all the check engine codes. then talk to flyskidsup. he is kind of new here, but knows the CCC carb setup and is less prone to say sell it on ebay and buy a 77-80 q-jet and vacuum-controlled distributor. but you need to know what all works and does not work with that system. as soon as it stops getting inputs, it is in limp mode. full rich on the metering rods and very basic 'centrifugal" advance only. gas mileage will suffer. your best bet may be to back date the car with pre ecm carb and distributor. your worst bet is to try to run it without all the inputs working. and worst-case? you put an O2 sensor in the exhaust. e4me and ecm test NFG. you get an earlier q-jet and HEI distrib. NOW you have a place to put the wideband oxy sensor to dial in your new carb correctly. a digital readout of fuel mixture is more accurate than looking at spark plugs...