I too have a high idle problem with my 75 280z, and can't seem to figure out what causes this problem. My car does not back fire, but it does seem to run very rich and it also will cut out suddenly with no warning at all. It then will not start until it is good and ready. I too would like to find out what causes these problems. I'm in the Phoenix AZ area, and would be appreciate some advice. DrR.
Very high idle
Hi everyone. While changing out my AFM 3 weeks ago something weird happened. The reason I was swapping them is because the one that is currently in the car has been tampered with to run richer and I wanted to put the stock one back on for fuel economy (gas is ridiculously high priced! 
)I put the stock one on and drove it for about 3 miles (generally to when the car was warming up) When sitting at a stop light by my complex i noticed the idle was sitting a little high; 1100-1200rpm. I pulled into my complex and went to turn down the idle air control and all of a sudden the car jumped to 1700rpm. I thought i must have knocked something off so i checked all of my vacuum lines (even propane tested) but to no avail.
I had my friend look at it and after tampering around a bit he found out that when he made a hot line go to the BCDD the idle would go back down. So obviously the BCDD wasn't getting power. We tested the line to see if I had somehow pinched it but it had good continuity. I then decided to try if i could get continuity directly from the main harness connector off the ECU to the end of the BCDD wire by testing every pin but I couldnt find any connection. I have gone through the FSM and the fuel injection bible but i cant manage to find a schematic of the BCDD circuit anywhere. All I could get out of the manual is that there is an amplifier on the back of the speedometer but I would rather confirm that that is where i need to start testing before I go and remove my entire dashboard.
Does anyone have any clues to what I should do? Or does anyone have a hidden schematic of the BCDD circuit? Im at a loss right now and currently have the BCDD hot wired which causes my car to backfire when its warm every time I change gears, so I'd really like to take care of this issue asap. Thanks in advance, Lionel
)I put the stock one on and drove it for about 3 miles (generally to when the car was warming up) When sitting at a stop light by my complex i noticed the idle was sitting a little high; 1100-1200rpm. I pulled into my complex and went to turn down the idle air control and all of a sudden the car jumped to 1700rpm. I thought i must have knocked something off so i checked all of my vacuum lines (even propane tested) but to no avail.I had my friend look at it and after tampering around a bit he found out that when he made a hot line go to the BCDD the idle would go back down. So obviously the BCDD wasn't getting power. We tested the line to see if I had somehow pinched it but it had good continuity. I then decided to try if i could get continuity directly from the main harness connector off the ECU to the end of the BCDD wire by testing every pin but I couldnt find any connection. I have gone through the FSM and the fuel injection bible but i cant manage to find a schematic of the BCDD circuit anywhere. All I could get out of the manual is that there is an amplifier on the back of the speedometer but I would rather confirm that that is where i need to start testing before I go and remove my entire dashboard.
Does anyone have any clues to what I should do? Or does anyone have a hidden schematic of the BCDD circuit? Im at a loss right now and currently have the BCDD hot wired which causes my car to backfire when its warm every time I change gears, so I'd really like to take care of this issue asap. Thanks in advance, Lionel
