I decided to run my '85 1.9l with the O2 sensor unhooked from the FI system and wired to my digital voltmeter. The readings were high, consistently ranging from 0.8 to 0.85 VDC. I then reconnected the O2 sensor and then "teed" in the voltmeter. The ECU adjusted the mixture some, dropping the voltage to 0.7 to 0.75 VDC. Is this still too high? Is it worth opening up the AFC and tinkering with the spring? A couple of interesting observations. The O2 sensor puts out a usable voltage in less than a minute---this is the one-wire type. I thought it would take several minutes to heat up. When you get off the gas, the O2 sensor voltage drops to almost nothing, and then recovers after a steady exhaust flow is established. It takes awhile at idle to level out. The WOT switch does work! It goes to 0.9VDC when you floor it--with or without the O2 sensor connected. My conclusion is that if your engine runs better with the O2 sensor disconnected, you have other problems. You probably have a vacuum leak and the richer open loop mixture helps correct it. How many notches should I move the AFC spring (and which way) to lean it out? This a new AFC, by the way. As a side note, I am running my timing at "0" TDC and it does seem to run better. I am hesitant to advance it much farther. Would this affect the O2 sensor readings? Jay '85 Westy |
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