Thanks. This is federal emissions. I have seen 2 degrees after for this car also, Under hood sticker says 7 BTDC, so I tried it both places, but seems to run best at 7 BTDC. Still blistering my plugs. Checked for air or vacuum leaks-none. Vacuum gauge held steady at 17 inches hg. At idle, and my altitude is about 2500 ft. Above sea level, if that matters.
My new O2 sensor has a 3 wire connector. I have not tried to test it since installed, about a month ago.
I was checking vacuum sensor operation per Chilton: voltmeter on terminal 9 to ecu should show 4 volts with no vacuum applied. I had near battery voltage-didn't write it down, just noted "batt voltage?". So did not proceed to applying 25 in, vacuum and checking for 0.5 volts. Took a coffee break, had a few smokes. Do I have a bad vacuum sensor? I checked voltage into the firewall mounted sensor (it has 3 wires: ground, signal from, and signal to computer. Well, that only middle wire had voltage and that was near battery voltage, like 12.0 volts, if I recall. Would the ecu send battery voltage to this sensor? When it is supposed to measure about 4 volts ranging down to about 0.5 volts as a signal to the ecu? So I'm at a loss, bad sensor or bad ecu?
Last question, if I check sensor again and note voltage with no vacuum applied, and then apply vacuum to sensor and note a voltage drop of about 3.5 volts, can I assume that sensor is working right, and that I have a bad ecu? Kinda hoping so, cause a remanufactured control unit is about $200, but their vacuum sensor is $420. And I only paid $300 for this 71,000 original miles Sentra, not running. Are map sensors critically calibrated, or can an old gm map sensor work just like my "vacuum sensor"?
Sunday, May 19th, 2013 AT 3:28 AM