1984 280SL - Surprising Smog Test Results

[ctaylor738]

Today I took my newest problem child in for its smog re-test. Car has 160K on it and smoked profusely. Following a head rebuild, I adjusted the mixture in the shade tree manner but leaning it until the idle started to decrease, and had it tested for emssions and it failed miserably.

Car had no plumbing or wiring for a lambda computer or frequency valve.

So, did the following:

- Cleaned injectors
- Installed an 87 degree thermostat
- Installed a Timevalve cat and header pipes with a fitting for a pre-cat O2 sensor
- Installed a Bosch single wire O2 sensor ($16.95) pre-cat. Ajdusted mixture to get close to the reference voltage of .45v, which according to the spec is the ideal 14.7 air/fuel ratio. Car runs very well but a bit sluggish.

The results of the re-test surprised me. Idle and 2500 RPM were very similar:

HC ppm: 26 Limit: 220

CO%: 0.00 Limit 1.20%

Basically near new car standards.

Who says these old hooters are polluters?

If I can find someone to do a NO reading, will do so and report. Also intend to use the sensor voltage to richen the mixture a bit to improve performance.