Hi, All, and thank you for a great forum! I posting here because my 1984 El Camino Conquista (305 V8/ 4 bbl) is failing smog test...on its first ever test.
The El Camino was purchased new by my father in San Francisco; as he lived in a non-biennial inspection county in California, the car was never smogged during his ownership; beyond religiously 3500 mile oil changes, he had the car serviced sporadically at a local good ol' boy shop. When he passed at 94 in 2013, I inherited it with probably 100k miles (odometer broken), and in California that doesn't require a smog inspection for in-family transfer of ownership.
The car remained registered in the non-biennial county until this year, when we sold the house. I now have to register it in San Francisco county, so it must pass smog....which it doesn't. All the factory equipment appears to be in place and the check engine light was not coming on, so I took it to a test-only local inspection station known for experience with older cars.
It passed all the visual inspections, and failed only NOx, with the following readings:
15mph CO2 13.7 O2 2.6 HC 30 (93 max allowed) CO 0.01 (.62 max) NO 1002 (783 max allowed)
25mph CO2 13.6 O2 2.7 HC 25 CO 0.00 NO 1018
The smog technician noted that the EGR valve appeared to be non-functional; manually lifting the diaphragm at idle had no effect, and the valve wouldn't hold vacuum with a hand pump connected to the EGR hose port, suggesting a broken diaphragm. He suggested having the EGR replaced and ensuring all the vacuum lines and sensor wires were intact.
I took the car to a mechanic who replaced the EGR, and found the coolant temperature sensor was defective, and replaced it and its connector. He also discovered the thermostat was missing, so he flushed the cooling system, installed a 180 degree thermostat and refilled with fresh coolant/water mix.
Following these repairs, the mechanic suggested adding a can of Sea Foam to the fuel tank and driving it around while before re-testing; added 16oz Sea Foam to 16 gallons gasoline and drove for 30 miles.
On the re-test, results were basically the same. The Smog technician suggested "adjusting the carburetor for a richer mixture" because the high NO was likely due to a lean mixture condition, and also consider replacing the O2 sensor. The mechanic suggested just driving it around some more with the Sea Foam, and felt there was no point in replacing the O2 sensor.
I found this excellent forum, and located the resource videos regarding CCC carburetor smog systems. I was particularly overwhelmed by the "CCC drivability" video, with it's punches and chisels on the carb base (at around 7:00) to access the mixture screws! Given the car's service murky history (and the absence of a thermostat), I looked at the carb on the car and sure enough, the base had been "serviced' with the plugs covering the mixture screws missing. I'm not familiar with the fuel circuits of a Quadrajet...are these the main jets?
So, what to do now? I'm fortunate that the smog shop will re-test at no charge (the technician is the owner and really likes El Camino's), but I'm reluctant to just fool around with the mixture screws and hope for the best. The "CCC Drivability" video mentions (at 9:06) that the mixture screws setting can be anywhere from 1.5 to 6 turns...given the high NO and low HC/CO, it IS likely that the engine's running lean and with high combustion chamber temperatures, but I'm unclear about the ECM's role in affecting air/fuel mixture in a CCC Quadrajet. No wonder they invented fuel injection!
Any help is appreciated; This car's been in my family since new, and I'd hate to retire it or give it up for an LS motor swap.
Thanks,
Marc
The El Camino was purchased new by my father in San Francisco; as he lived in a non-biennial inspection county in California, the car was never smogged during his ownership; beyond religiously 3500 mile oil changes, he had the car serviced sporadically at a local good ol' boy shop. When he passed at 94 in 2013, I inherited it with probably 100k miles (odometer broken), and in California that doesn't require a smog inspection for in-family transfer of ownership.
The car remained registered in the non-biennial county until this year, when we sold the house. I now have to register it in San Francisco county, so it must pass smog....which it doesn't. All the factory equipment appears to be in place and the check engine light was not coming on, so I took it to a test-only local inspection station known for experience with older cars.
It passed all the visual inspections, and failed only NOx, with the following readings:
15mph CO2 13.7 O2 2.6 HC 30 (93 max allowed) CO 0.01 (.62 max) NO 1002 (783 max allowed)
25mph CO2 13.6 O2 2.7 HC 25 CO 0.00 NO 1018
The smog technician noted that the EGR valve appeared to be non-functional; manually lifting the diaphragm at idle had no effect, and the valve wouldn't hold vacuum with a hand pump connected to the EGR hose port, suggesting a broken diaphragm. He suggested having the EGR replaced and ensuring all the vacuum lines and sensor wires were intact.
I took the car to a mechanic who replaced the EGR, and found the coolant temperature sensor was defective, and replaced it and its connector. He also discovered the thermostat was missing, so he flushed the cooling system, installed a 180 degree thermostat and refilled with fresh coolant/water mix.
Following these repairs, the mechanic suggested adding a can of Sea Foam to the fuel tank and driving it around while before re-testing; added 16oz Sea Foam to 16 gallons gasoline and drove for 30 miles.
On the re-test, results were basically the same. The Smog technician suggested "adjusting the carburetor for a richer mixture" because the high NO was likely due to a lean mixture condition, and also consider replacing the O2 sensor. The mechanic suggested just driving it around some more with the Sea Foam, and felt there was no point in replacing the O2 sensor.
I found this excellent forum, and located the resource videos regarding CCC carburetor smog systems. I was particularly overwhelmed by the "CCC drivability" video, with it's punches and chisels on the carb base (at around 7:00) to access the mixture screws! Given the car's service murky history (and the absence of a thermostat), I looked at the carb on the car and sure enough, the base had been "serviced' with the plugs covering the mixture screws missing. I'm not familiar with the fuel circuits of a Quadrajet...are these the main jets?
So, what to do now? I'm fortunate that the smog shop will re-test at no charge (the technician is the owner and really likes El Camino's), but I'm reluctant to just fool around with the mixture screws and hope for the best. The "CCC Drivability" video mentions (at 9:06) that the mixture screws setting can be anywhere from 1.5 to 6 turns...given the high NO and low HC/CO, it IS likely that the engine's running lean and with high combustion chamber temperatures, but I'm unclear about the ECM's role in affecting air/fuel mixture in a CCC Quadrajet. No wonder they invented fuel injection!
Any help is appreciated; This car's been in my family since new, and I'd hate to retire it or give it up for an LS motor swap.
Thanks,
Marc