I was trying to adjust the mixture to pass emissions, and I did something that I can't figured out. The is a '81 240 with a B21F(K-jet). Last year I had to adjust the mixture to get it pass emissions. It passed within limits (well inside limits).

Before I messed with it this year, the dwell with the oxygen sensor connected at idle was ~25, and the dwell with the oxygen sensor disconnected was ~60. This should mean that the mixture is too rich, so I tried to lean it out by rotating the mixture screw counterclockwise (I can't every tell if the allen wrench is on the screw or not).

After messing with it, the dwell with the oxygen sensor connected at idle is ~82, and the dwell with the oxygen sensor disconnected is ~60. With the oxygen sensor connected and the engine speed is increased, the dwell drops to ~35. I checked the voltage at the oxygen sensor (connected), and at idle the voltage is ~ 0.05, and when the engine speed is increased, the voltage increased to 0.90. This should mean that the mixture is too lean, so I tried to make it rich by rotating the mixture screw clockwise, but nothing in the readings change (And again, I can't tell if the allen wrench is on the screw or not).


Any ideas with what is wrong?? I did replace the oxygen sensor, but readings are the same.

Paul