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Discussion Starter · #1 ·
Does anyone know how I can adjust the Air Flow Meter on my 78 280Z without having to take it into a shop?

Z-folks I've talked with can only say ...take it to a shop that has a CO meter to measure the exhaust gasses....

Isn't there another way? There's no way at all to set that potentiometer thing using a volt-ohmmeter or something?

I can't spend much money on the car (already spent too much), so taking it to a shop really isn't the preferred solution. I'd rather spend 5 hours fiddling with a volt-ohmmeter than $75.00 taking it to a shop.

-Rob
 

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Discussion Starter · #2 ·
Take the black cover off the AFM and loosen the screw that holds the cog. Be careful it's under tension and will unravell if you don't hold the cog while you loosen the screw. If you move the cog to the left it will cause the door flap to more with less resistance. Don't move it too much (one or two tooths)as it will throw off you air fuel mixture. Hope this helps.
 

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Discussion Starter · #3 ·
> Take the black cover off the AFM and loosen
> the screw that holds the cog. Be careful
> it's under tension and will unravell if you
> don't hold the cog while you loosen the
> screw. If you move the cog to the left it
> will cause the door flap to more with less
> resistance. Don't move it too much (one or
> two tooths)as it will throw off you air fuel
> mixture. Hope this helps.
Rob,
There is only one adjustment for the AFM. The discription above is an old racer trick to richen the mixture by fooling the ECU into thinking the engine is getting more air than it is. Although it does effectively do this I doubt that it does what you were thinking. Actually the only adjustment is to a screw (slotted) in a hole on the side of the AFM facing the coil. This adjusts the amount of air that gets through with the AFM flap closed. In fact you do need a CO meter to adjust this accurately but you could fiddle with it and ballpark it. They come preset from the factory so it shouldn't need too much. What are your symptoms?
 

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Discussion Starter · #4 ·
> Rob,
> There is only one adjustment for the AFM.
> The discription above is an old racer trick
> to richen the mixture by fooling the ECU
> into thinking the engine is getting more air
> than it is. Although it does effectively do
> this I doubt that it does what you were
> thinking. Actually the only adjustment is to
> a screw (slotted) in a hole on the side of
> the AFM facing the coil. This adjusts the
> amount of air that gets through with the AFM
> flap closed. In fact you do need a CO meter
> to adjust this accurately but you could
> fiddle with it and ballpark it.
> They come preset from the factory so it
> shouldn't need too much. What are your
> symptoms?

I should've asked, How do I determine, using driveway mechanic's tools, exactly where to set the potentiometer to make the AFM be properly set to mix the correct amount of fuel?

The car flunked smog (terribly, gross polluter, way way too rich). Before it flunked smog it sat for 2 years not running, then I pulled the head to repair it, then put it back together. During reinstall I took the cover off the AFM and unscrewed the phillips head screw holding the white plastic gear on the potentiometer. I tried to reset it by simply fiddling with the car running, and setting it where the engine seemed to run best. Then I smogged it, and it flunked badly.

I'm working through the multiple other sensors and controls one by one, but since I already fiddled with the AFM I want to know how to properly set it. I have extracts from the service manual that cover the AFM, but it doesn't say here's how to set the thing with the car sitting in your driveway and with only common household tools.

The whole point might be moot anyway, because about 2 hours ago my Z started sounding like either the transmission was falling off or like engine parts were loose inside the block and bouncing around. I limped home, parked it, and I'm considering giving up on it and selling it for whatever I can get. No fun anymore working on a car that isn't cooperating....
 

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Discussion Starter · #5 ·
> I should've asked, How do I determine,
> using driveway mechanic's tools, exactly
> where to set the potentiometer to make the
> AFM be properly set to mix the correct
> amount of fuel?

> The car flunked smog (terribly, gross
> polluter, way way too rich). Before it
> flunked smog it sat for 2 years not running,
> then I pulled the head to repair it, then
> put it back together. During reinstall I
> took the cover off the AFM and unscrewed the
> phillips head screw holding the white
> plastic gear on the
> potentiometer. I tried to reset
> it by simply fiddling with the car running,
> and setting it where the engine seemed
> to run best. Then I smogged it, and it
> flunked badly.

> I'm working through the multiple other
> sensors and controls one by one, but since I
> already fiddled with the AFM I want to know
> how to properly set it. I have extracts from
> the service manual that cover the AFM, but
> it doesn't say here's how to set the
> thing with the car sitting in your driveway
> and with only common household tools.

> The whole point might be moot anyway,
> because about 2 hours ago my Z started
> sounding like either the transmission was
> falling off or like engine parts were loose
> inside the block and bouncing around. I
> limped home, parked it, and I'm considering
> giving up on it and selling it for whatever
> I can get. No fun anymore working on a car
> that isn't cooperating....

Hope I can help

I don't know if I can help with the emission problem, but I should be able to get it running properly.

#1 start with the car at operating temp.

#2 remove the cover on the Air flow meter

#3 set the mix screw ( air bypass scew) to the middle.

#4 move the the pot. left and right. one way it will rev the engine slightly then die off, the other it will start dropping off right away.

#5 once you have determined witch way it has to go, adjust the bypass screw untill you are right at the peak rpm. then adjust it slightly rich, no more than a quarter turn.

this should set your mass air flow sensor where it is delivering what the engine wants in fuel.

The engine is going to take in what ever volume of air it wants. The M.A.S. just determins how much fuel to deliver acordingly. So if you set it to the left more, you will lean out the mix, to the right, you will richen the mix.

Hope this helps.

Will.
 

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Discussion Starter · #6 ·
Clarostat to Richen Fuel Mixture???

I too have been considering adjusting my AFM in my 83ZX N/A, since purchasing a performance throttle body. When I received the throttle body, the guy who I bought it from was nice and threw in a clarostat (just a variable resistor), which will allow me to make my fuel mixture more rich. Do I still need to modify the AFM, or should this clarostat work instead? Thanks.
 

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Discussion Starter · #7 ·
> Hope I can help

> I don't know if I can help with the emission
> problem, but I should be able to get it
> running properly.

> #1 start with the car at operating temp.

> #2 remove the cover on the Air flow meter

> #3 set the mix screw ( air bypass scew) to
> the middle.

> #4 move the the pot. left and right. one way
> it will rev the engine slightly then die
> off, the other it will start dropping off
> right away.

> #5 once you have determined witch way it has
> to go, adjust the bypass screw untill you
> are right at the peak rpm. then adjust it
> slightly rich, no more than a quarter turn.

> this should set your mass air flow sensor
> where it is delivering what the engine wants
> in fuel.

> The engine is going to take in what ever
> volume of air it wants. The M.A.S. just
> determins how much fuel to deliver
> acordingly. So if you set it to the left
> more, you will lean out the mix, to the
> right, you will richen the mix.

> Hope this helps.

> Will.

I know we all tend to see things in terms of our own universe but I feel compelled to point out that Rob is talking about his 78 L6 Z Coupe here. There is no air mass sensor on a 78 Z. It is an air flow meter which is simply a potentiometer that reads a varied flap position and sends a signal to the ECU based on that flap position. An Air Mass Sensor is an entirely different and more advanced concept. There is only one legitimate adjustment to an air flow meter. Any other adjustment is an invitation to driveability nightmare unless you are lucky and luck is rare in these curcumstances. The only real adjustment is to turn the by pass screw to allow more or less air in at idle. He is trying to pass smog here not win an autocross. More than likely from his discription which he e-mailed me privately it is not an air flow meter problem.
 

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Discussion Starter · #8 ·
> Take the black cover off the AFM and loosen
> the screw that holds the cog. Be careful
> it's under tension and will unravell if you
> don't hold the cog while you loosen the
> screw. If you move the cog to the left it
> will cause the door flap to more with less
> resistance. Don't move it too much (one or
> two tooths)as it will throw off you air fuel
> mixture. Hope this helps.

That's what I did made a big difference in performance. Not sure about smog don't have inspections where I live. You can fine tune it with the screw on the side. Sam 75 280z
 
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