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That's the question. How do you adjust the air/fuel mixture on a 78 280. Thanks for any help
 

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What type of problem are you having first off. If it is running bad or acting up it could be a number of things. I have been working on my 78 for 4 months trying to get it tuned in to my satisfaction and am really close..
 

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> What type of problem are you having first
> off. If it is running bad or acting up it
> could be a number of things. I have been
> working on my 78 for 4 months trying to get
> it tuned in to my satisfaction and am really
> close..

I had to adjust the AFM spring internally then fine tune with the screw on the side of the AFM. First check and clean all other sensors to make sure some aren't faulty then mess with mixture.

Sam 75 280z
 

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> That's the question. How do you adjust the
> air/fuel mixture on a 78 280. Thanks for any
> help
If you want to richen your mixture you can insert a low ohm resistor (start with 10 ohm) inline with your water temp sensor. The ECU then thinks the engine is colder than it really is and richens your mixture. The higer the impedance the more rich the ECU will make the mixture.

Don
 

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Don is right about this part of it.. I started with 600 ohm and went down to a 165 ohm. Installed the K&N RU-0900 air filter and now running with no resistor and a few tweeks to the AFM adjustment screw.. Works for me..
 

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> Don is right about this part of it.. I
> started with 600 ohm and went down to a 165
> ohm. Installed the K&N RU-0900 air filter
> and now running with no resistor and a few
> tweeks to the AFM adjustment screw.. Works
> for me..
Gosh, what an interesting bunch of answers! The air/fuel mixture is adjusted by turning the air bypass screw indented in a hole on the side of the air flow meter. This screw is facing the tail of your coil facing toward the driver fender. Now this only adjusts the amount of air that is getting through when the car is at idle and the flap is shut. It is factory adjusted and shouldn't need adjustment. In other words you are not enriching or leaning the mixture during open throttle. Strictly speaking you cannot adjust air/fuel mixture. You can trick the ecu and that is what is done with spring tightening and resistors. Tightening the spring will richen up the mixture as will resistors and increasing fuel pressure which can be done as simply as putting a crimp in the return tube but what is your actual problem and what are you trying to accomplish? Most people are blaming the EFI system for other problems. Most often the problems are vacuum, fuel delivery or electrical. I have even seen a Porsche race car with whitish blue-green cheese all over the connectors under the hood. It wouldn't start for his race session! Big surprise!
 

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> That's the question. How do you adjust the
> air/fuel mixture on a 78 280. Thanks for any
> help

Rick, there really isn't a need to adjust the mixture. That's what the ECU does, you can trick it to thinking the engine is cold, but this can cause side affects including poor milage and fouled plugs,or worse. The ECU receives inputs from various sensors and contols the fuel mixture by controlling the injector pulse speed, and width. If you are experiencing a drivability problem, get your hands on a Nissan shop manual, the have a great troubleshooting guide. I have the fuel injection chapter copied if you have a hard time finding it. It may be that one of your sensors is out of tolerance, or you could have a low flow situation on one or more injectors(that's what my problem was). New injectors, and I was rockin' Good luck. TIM
 
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