Adjusting the air flow meter on old EFI's

[datzenmike]

Does anyone have any experience adjusting the air flow meter on an old (pre '84) car like the 280zx or 200sx? This is the old Bosh Jettronic? batch fire system using an air flow meter consisting of a flap that is pushed and rotated by the entering air. The flap valve rotates a variable resistance sending a signal to the ecu dependent on the air volume entering the motor. A friend has put this system on a larger Z24 motor and is having problems getting it to idle and run properly. It does run, but poorly.

 

Does anyone have any info or theory on which way to turn the adjustment to richen or lean the mixture? How much? Ideas?

 

thanks.

[athoose]

Just came across this.

 

http://www.geocities.com/jfairladyz/AFMrebuild.html?1144191577198

[Z-train]

Mike- i just did this to my 810.I'm headed for Yuma right now.Get ahold of me on Monday.

[athoose]

You may also want to check the AFM per the service manual procedure, for proper operation. All you need is a voltmeter. You need the specific FSM for pin location and resistance/continuity specs and checks. I have them for 80/81 200sx if needed.

[SHADY280]

its really not as hard as it seems. if you really want to get it right you need an air/fuel wideband, but can always use the spark plugs for a good idea. its basically pull the side off and adjust the spring tension. tighter is lean, looser is rich, kinda like a carb. just dont let the flapper go when you loosen the set screw. count the teeth that you move and go for a good drive. use the seat of you pants as well, but we all know how accurate that is. look out the mirror for black smoke, or blue if you over rev!

[datzenmike]

You may also want to check the AFM per the service manual procedure, for proper operation. All you need is a voltmeter. You need the specific FSM for pin location and resistance/continuity specs and checks. I have them for 80/81 200sx if needed.

 

I sure would like that. Can you p/m them to me. After modifying it would be great to check the readings.

 

thanks.

[athoose]

PM sent. Let us know how it worked out.

[HP11]

I have an exhaust gas analyzer that I use when/if I do that adjustment. It's really a good idea to use something whether it be an analyzer or an an air/fuel wideband as SHADY280 mentions. 'Seat of the pants' really isn't accurate enough. The only time I ever look at that is prior to s smog check.

[Bleach]

I just marked with a black pen on the white gear where I started. Adjust a couple teeth more rich and then let the engine run. If its warmed up and you can open the throttle all the way suddenly without any backfire then its close. :)

Also make sure your timing is accurate and that your vacuum advance works before even messing with fuel.

[datzenmike]

Thanks Kevin, I'll pass that on too.

[Bleach]

also, upgrade to a Nissan EFI that uses a MAS. so much better. (if possible)

 

I'm doing the Z31 swap on my turbo 280ZX this year.

[datzenmike]

Yes, my plans are to use KA throttle on 200sx manifold:

KA top 200sx bottomhttp://i138.photobucket.com/albums/q251/datzenmike/720%20stuff/720ECU007Large.jpg[/img]"]

 

Bored out throttle chamber:

http://i138.photobucket.com/albums/q251/datzenmike/720%20stuff/720ECU012Large.jpg[/img]"]

http://i138.photobucket.com/albums/q251/datzenmike/720%20stuff/720ECU014Large.jpg[/img]"]

 

Finished product:

 

The rest of the wire harness/ECU and sensors are from the 240sx.

 

A buddy in northern BC is just swapping the complete 200sx EFI onto his Z24. This is who needs the info. Thanks again for your help.

Edited March 24, 2009 by datzenmike