Air Flow Meter Question

[ferniespider]

I have a 1982 spider with 25000 miles. When I bought it it was hardly running at all - Some electrical issues.

My mechanic couldn't get it to run right and suggested replacing ECU. I did this it still did not run right. The injectors weren't right so I replaced them with rebuilt ones. Still not running right. Plugs are very black - running Very rich.

I checked my Air Flow meter (AFM)
Resistances for terminal numbers
7 - 8 measured 1377 should be less than 1200 ohms
6 - 8 measured 446 should be less than 600 ohms
9 - 8 measured 246 should be less than 300 ohms

When I moved the airflap and monitored resistance on 7-8 the resistance jumped around all over the place - down to 100 then up to 1200 and everything in between. I concluded the AFM had some problems

I ordered a remanufactured AFM. I plugged it in no luck the car won't run at all

I measured the Resistances (with flap closed)
7-8 181 ohms seems very low (Max is 1200)
When I moved the flap the reistance climbed to 1000 (flapped moved 1.25" as measured with a dowel oushing the flap)with some jumping around then decreased to 350 full open
6-8 206 ohms (Max is 600)
8-9 117 ohms (Max is 350)

I think the reman unit is defective based on these resistance numbers - Any insights out there?

I played with my old AFM while I was waiting for the reman unit and I managed to make it worse so it doesn't work now as well

I live in Canada and winter is coming soon. I would like to drive this car before the snow falls.

[2ndwind]

Fernie,
My car ran poorly when I first got it so I paid the big $$ for a rebuilt one too. Replaced, Auxiliary Air Flow Valve twice, and temp sensor in coolant tee, I still had problems with the idle which eventually turned out to be a cracked air intake hose and poor idle screw o ring. Now it won't idle below 1400 RPM with the accelerator stop screw backed completely away from the stop. New information came to me via buying a second spider.

My other FI spider wouldn't hold an idle AT ALL and I could barely keep it running when cold. I had to keep revving the engine to 3-4000 with the accelerator for 5-8 min till it was warmed up, often it would choke itself out during this period. It ran fine once it reached 140 degrees. I took all the readings at the ECU and everything was within spec. Now What? On a whim, I switched with the AFM off my first spider and VOILA! it ran perfectly and at 1400 rpm idle. That is when I discovered the rebuilt AFM is causing the 1400 RPM at idle. I was lucky enough to buy a used, working AFM from George K. parting a car on this forum. When I installed the used AFM, the car runs perfectly. I even switched it with my first car and ended up with the proper 950 rpm idle, no problem. Apparently there is a temperature sensor inside the AFM that is not serviceable.

So now I am terribly biased and tell everyone to find a KNOWN good AFM from a well-running car put it on your car and try that first.

[CarlosJavier]

The measurement between ECU terminals 7-8 is the resistance between an electric sweeper and a swept arc surface found under the black lid on top of the AFM. The sweeper is attached via a shaft to the AFM flap, so they move together.

If you open the AFM lid and press the sweeper onto the swept surface you can bring the resistance between ECU terminals 7-8 within spec.

Regarding the changes in resistance between terminals 7-8 as you move the AFM flap, that is normal. The changes in resistance let the ECU know how open the flap is, and thus how much air is entering the engine.

[divace73]

My experience with the AFM was that the arm that sweeps 'wore' a track into the PCB, I just moved the PCB a little so it would seewp on a new unworn track that would cross all the necessay resistance paths. That seemed to work.
ALso check the IAT (intake Air temp sensors) and compare the 2 units you have. Test the resistance in ambient air, then pop them in the fridge and do the same and compare the two.
If you pm me I can send you some other pdf's that may help.

I hope this helps

Cheers
David