[JMH82SC]

I have decided to hook up my O2 sensor and play with the stock set up to see what I can get for gas mileage. I have searched and invested many hours of reading and feel I have a good understanding of the CIS system. For background I have replaced all rubber relating to the system when I did the engine rebuild and do not have any vacuum leaks. I had my CO set to 3.5 at a local shop and car runs well OPEN LOOP and I do not have any issues but I just want to give the Lambda system a shot. I have tested system and control pressures and WUR is in spec.

My first impression with O2 plugged with CO still set 3.5 is a chugging effect with light throttle at constant speeds. This chugging is not bad and I have heard it described like pulling a trailer ( push pull thing.) One good thing is I do not have as much of a rich smell at idle because Lambda is pulling mixture lean at idle (? 45-50?).

As for testing I have a MAC EM710 digital volt meter that has both dwell and duty cycle settings. With all testing done with + at the green and white wire at test port and – grounded to engine I get 50% duty cycle with open loop I get 50% (normal). With car cold I do not get the 65% duty cycle but it is 80 degrees here so the cold start switch is not grounded because it is too hot. If I ground the wire for the switch I do get 65% cold start value. The only thing that has me scratching my head is if I ground the Lambda O2 wire I do not get 90% I get 70 or so. Because I do not get the 90% with Lambda wire grounded does this point to the brain? If it is the brain could this be the reason for chugging effect?