AFM Vane/Flap

[55Dave124]

Hi All, First time poster here. Just got a 1982 124 spider that had not been driven much lately. It is running rich at idle and has a slight misfire. I checked the plugs, (black but not oily) and cleaned out the AAR valve which seems to be working OK. I am changing the plugs and 02 sensor. The AFM flap is open at rest, is it supposed to be closed at start? It is open about 3/4 inch, is that normal? It also offers no resistant to close it to the right against the spring pressure. If i remove the main intake hose the car will fire for a second than dies. I cannot see if the flap closes or not. If I increase the rpm to 1500 with the main intake hose on it runs good. All the vacuum hoses have been replaced so as to eliminate any vacuum leaks. Thanks in advance to all posters, I have learned alot about this car from this forum.

[18Fiatsandcounting]

The first thing that I would check is the Coolant Temperature Sensor (CTS), the one on the coolant neck at the front of the head (not the ones next to the spark plugs). Sometimes the electrical plug connection simply goes bad.

I would think the AFM would close all the way, but I'm not an expert on FI systems. Maybe someone else is. And yes, if the rubber "ducting" from the AFM to the throttle body inlet is disconnected, the AFM doesn't sense any air flow, and the ECU shuts off fuel to the injectors.

-Bryan

[55Dave124]

Thanks, I'll check that out.

[55Dave124]

Ok, I checked the Ohm resistantance with my multimeter at the CTS. It read 1750 Ohms at 92 degress F. ambiant air temp, engine cold. Does this sound right?

[18Fiatsandcounting]

That sounds right. I found a reference that says the resistance should be:

Between 7000 and 11600 ohms at 14 oF
Between 2100 and 2900 ohms at 68 oF
Between 270 and 390 ohms at 176 oF.

So, it looks like the resistance of your CTS is right in that range, so that's likely not the problem. Check the wiring connector, though.

-Bryan