I know not another backfire through intake 1976 280z I think I tested it all

[240260280z]

Racebird, I am so glad to read your post and to know the crazy calibration tests I did many years ago are helping others! Thanks for your data too above.... good stuff in it for the Z community!

[cozye]

Specific afm's are supposed to be paired with specific ecu's . They aren't necessarily going to work with your ecu. You will need to make sure that the serial number AFM you have is compatible with the serial number ecu you at going to use. Once you have calibrated via blues method, you should leave the AFM alone. It's not a great method to use that adjustment to make the car run richer, as it will require somewhere around 12 teeth or more to get the air fuel right, and the AFM spring will not have enough tension at that adjustment to work properly at higher air flow. Several of us have tried that, and the fueling gets way off at higher rpm. It will have no power at all end get like 12mpg.

The best way is to put the potentiometer in the water temp circuit. Is there a reason why you don't want to try this?

[FastWoman]

Blue, yes, your crazy beer-can clockspring calibration method has helped quite a few of us. I've used it, as have Cozye, argneist, Zed Head, and probably countless others. Zed Head and I even played around with a refinement of the method using (US) pennies, which admittedly vary in weight by year.

Racebird, hook up your best AFM, leaving the cover plate off, start the engine, and carefully finger the AFM's mechanism a bit more open to provide more fuel. Idle should pick way up, and the engine should smooth out. That's an easy preview of what the potentiometer will do for you.

[racebird1]

Hey blue the calibration method took a ton of time to produce and I really appreciate the time you put into it. I will be using to the pot adjustment and I have one on order and should have it in a day or two. I have not decided where I am going to put it yet. Mybe temporarily under the hood then move it to the ECU area. I am going to order the new injectors so I can be sure that they are giving me the right amount of fuel. The two older afms don't have the serial number on them but both newer ones do. I am going to try one of the older ones since one of them was from the car and I have it calibrated to Blue's method. Since I am so close to it running pretty decent now these changes should get me where I need to be for awhile.

[racebird1]

I haven't had any spare time to get some of the changes to the car done yet this week so I can see if anything improves. My new E-bay injectors arrived today, that only took three days to get here so hats off for good service and the hoses are plenty long enough and I will even need to shorten them because they have about 3" of hose on them so naturally I was glad to see that. They look great and I hope they work as well as they look. My potentiometer my be here as well so soon as I get time I will try these changes and see how it goes.

[racebird1]

I finally got back to the Z today and did some more checking. I found that the cold start injector is not injecting. I pulled it out and checked it when my son started the car and nothing. It put my injector tester lead to it gave it power and it works fine but not when I start the car. I will need to look into the thermo time switch. I tested the main injectors a litttle differantly, I pulled the fuel rail and and turned the key to on and fingered the AFM enough to get the pump on then powered up the injectors up one by one and they all sprayed great so I don't think the injectors were bad after all. I installed the new ones anyway. I advanced the timing to about 25 degrees cold and the vacuum went up to 18 inches but the engine races too much so I backed it down to 20 and I don't get any intake backfire. I also fingered the AFM all the way when it was running and it bogs down the engine from being too rich so I think that is working fine as well. I will install the pot switch this week and see if that will help.