Bad Air Flow Meter?

[Lani Kai]

I'm suspecting my air flow meter has gone bad. The car is running rich and occasionally stutters at high RPM, generally past 4,000. I've looked at just about everything else that factors into setting the fuel mix but I want confirmation before replacing the AFM because it's not a cheap part and only available on a core-exchange basis from MSA.

Is there anyone in Orange County, CA with a healthy AFM that I can borrow and test before I needlessly spend money? I'd reimburse you for gas costs and provide a beer or something

[Darrel]

Why don't you test your old one? It's all in the factory service manual and can be diagnosed with a multimeter.

go to the zenon web site for manual downloads and the efi bible.

[grantf]

have you tried this? http://atlanticz.ca/zclub/techtips/afm/index.html

[FastWoman]

It's a rather simple device, so I'd also test it and clean it up. In addition to the FSM tests, I'd use a mechanical (needle) type of multimeter to measure the resistance from one end of the potentiometer to the wiper contact, throughout the entire sweep of the potentiometer. You want to see the resistance move smoothly, with no stuttering or gapping in the needle movement.

Things that I'd also check, if you haven't already:

-- Stuck cold start valve.

-- bad thermotime switch

-- misadjusted or malfunctioning throttle position switch

Also pull your plugs and see if they all read the same. You might have a problem that affects only some cylinders.

FAIW, it's more common for these machines (particularly the '78's?) to run lean. A severe lean condition will give you carbon fouling of the plugs, owing to incomplete combustion, so it might look like a rich condition. Do you get backfiring through either the exhaust or the intake? If you have backfiring through the intake, you might have a severe lean condition. Backfiring through the exhaust would probably indicate a rich condition.

[darom]

You don't need to buy an AFM from MSA. I got mine from Amazon for $150 shipped. Of course, per previous posters' advice, test your electronics first before committing cash.