Hunting down Fuel Injection issues

[BA2000FI]

Hello,

So I have been trying to diagnose why my engine has been misfiring / running rich. I've replaced Sparkplugs, Air Filter, Starter, Fuel Filter, Oil Filter and Oil Change. This helped but the car still idles high and will almost cut out when I give any throttle input. I measured the CTS at ~78 Degrees F to be ~2100 ohms at both the sensor itself as well as at the ECU Connector. Checked the voltage from the cold start valve and its getting volts on cold start (have not checked it at temp to see if its cutting off properly). Checked the AFS at the ECU connector and im getting ~360 ohm on pins 6 to 8, ~3000 ohms on pins 7 to 8, and ~200 ohm on pins 8 to 9. The 7 to 8 value seems all out of line so am I safe to assume that the AFS is the issue? When I pulled the unit out of the car it seems like the "door" inside is stuck open. Is there anything else I should check first?

-Brysen

[TheBender]

Have you taken a look at the fuel injection trouble shooting guide on Mirafiori? If not, might be a good source of information for you.

[BA2000FI]

Have you taken a look at the fuel injection trouble shooting guide on Mirafiori? If not, might be a good source of information for you.

Yes, i have followed those steps. That’s where I get the idea that the AFS is the issue

[18Fiatsandcounting]

When I pulled the unit out of the car it seems like the "door" inside is stuck open.

Do you mean the flap inside the AFS is stuck? It should move proportionally to the amount of air rushing by, thus varying the voltage signal it sends to the ECU. If that flap is stuck open, the ECU thinks the engine is at wide open throttle and sends a lot of gas through the injectors. That's likely the reason you're running rich.

-Bryan

[BA2000FI]

When I pulled the unit out of the car it seems like the "door" inside is stuck open.

Do you mean the flap inside the AFS is stuck? It should move proportionally to the amount of air rushing by, thus varying the voltage signal it sends to the ECU. If that flap is stuck open, the ECU thinks the engine is at wide open throttle and sends a lot of gas through the injectors. That's likely the reason you're running rich.

-Bryan

Yes the flap moves but it doesn't return to a closed state when the engine is off. So that makes sense, I just need to replace it and hopefully it solves my issues

[spider2081]

Curious what model year you Spider is. I thought Fuel injection models started in the later part of the 1980 model year. I think a 1979 Spider would have left the factory with a carburetor not fuel injection. Is this a modified Spider?

[18Fiatsandcounting]

Yes the flap moves but it doesn't return to a closed state when the engine is off.

Maybe the return spring is broken or popped loose from its mounts? Wouldn't hurt to pop the cover off and see what's going on with the flap.

-Bryan

[BA2000FI]

Yes the flap moves but it doesn't return to a closed state when the engine is off.

Maybe the return spring is broken or popped loose from its mounts? Wouldn't hurt to pop the cover off and see what's going on with the flap.

-Bryan

So I popped open the cover, and started taking a look. I have a background with electronics and the mechanism is pretty simple so I took all the electronic components out and everything looks good from a quick glance. The return spring is operating fine, but with tension from the spring removed the door itself is rough to move and makes an awful squeaking noise so I think that may be my problem. Not sure if anyone has tips on cleaning the unit and lubricating that pivot.

For reference this is as far as I have disassembled the unit
https://drive.google.com/file/d/1Oot-z5 ... sp=sharing

-Brysen

[BA2000FI]

If anyone knows how to safely remove the return spring as shown in the above link that would be great

Edit: I figured it out it just pulls off

[18Fiatsandcounting]

I've never taken one apart, so I'm probably not much help here. I'm guessing the collar that holds the spring around the shaft is pressed on, and you probably don't want to try and remove that lest it end up breaking. If all the plastic and electronic components are removed, I'd soak (or the spray) the whole assembly in degreaser and try to get it as clean as you can. See if you can see rust on the shaft for the vane. If there's rust, there may not be a good fix. After cleanup, you could try dripping some oil onto that shaft and work it around and see if it helps. Oil is also a good way to remove light rust with some gentle abrasion.

I don't have a good suggestion for a "permanent" grease for the shaft, as there probably wasn't any originally. Maybe some spray lithium grease?

-Bryan

[BA2000FI]

Yep it came off with little to no force. I cleaned the unit well and found the issue. The axel the vain sits on is slightly bent so the edges of the vane are getting stuck on the housing of the unit

[BA2000FI]

Final update!
I replaced the washers in the AFM and it allowed just enough clearance for the vain to move freely. Put everything back together turned the key and the car started right up and is running smooth as day! Only issue now is it’s running a tad bit hot and the radiator fan doesn’t seem to be kicking on not sure if it’s a bad sensor or fan motor but hopefully it’s an easy fix.

[18Fiatsandcounting]

Only issue now is it’s running a tad bit hot and the radiator fan doesn’t seem to be kicking on not sure if it’s a bad sensor or fan motor but hopefully it’s an easy fix.

Awesome on the air flow sensor fix! As to your question above, it is an easy fix, but you'll find endless posts on the overheating issues, especially with the 2L engine. Reason being is that the 2L engine sits taller than the earlier engines, that is, taller relative to the radiator which is where you add the coolant. So, it's easy to get an air pocket in the top of the cylinder head which leads to the cylinder head temp sensors reading high. Another common air pocket is in the lower radiator hose leading to the thermostat. Also not good.

Search on this forum for the various solutions to this, which include raising the front of the car as you fill the radiator, adding a coolant "T" in the heater hose at the back (the best solution), and burping the system.

-Bryan

[spider2081]

Great to hear your Spider is running again.