The stumbles.

[JConnerly]

Recently had the valves adjusted on my 81 FI and overall it is still running better than since I got it a year ago. The fouling of plugs one and two has stopped and combustion seems to have improved. Three weeks later two problems have arisen and I don't know if they are related or not.
1. Temp gauge shows the engine running cool, around 130- 140. Spot check with an infrared meter shows normal engine temp with the fan coming on at just over 190. Have a new thermostat. There was a little break in the insulation on the rear temp sensor and I noticed oil on the connector (probably from spillage during the valve adjustment). Have cleaned both sensor connectors and repaired the broken insulation. No change.
2. About a week ago it began stumbling at about 2200 RPM when just cruising. Isn't noticeable at idle, isn't there at higher RPM. Went 75 on the freeway without problems. Have just changed the spark plugs. Have new wires this spring and the cap and rotor are a year old. Timing was set at 15 degrees at the time of the valve adjustment because my vacuum advance is toast. Fuel filter is new. I did notice a black greasy residue in the throttle body around and behind the butterfly. Don't know if that was there before.
Thoughts?

[narfire]

I'd be thinking the temp sounds fine. Mine, in air temps of 30-35 deg C here, the engine while driving, is around what you stated. In the Tim Horton's drive through line ups it spikes at 190, fan comes on and pretty much stays there till the wankers in front of me finish ordering for the office and I get moving again.

Second issue... I'm trying to make a somewhat educated guess here but hows the O2 sensor, been replaced?
Ok second thing I'd check is if the flap on the AFM is sticking a bit. Perhaps there might have been a bit of a backfire once upon a time and it could have tweeked the flap in the afm and sticks at that opening when engine is at that rpm.
Just a guess
Chris

[rlux4]

This may or not be it, but I had this issue and it was a bad spot on the resitance track in the AFM. I loosened up the set bolt on the sweep arm and pushed it down the shaft ever so slightly and it cleared right up. This sets the sweep arm into contact with a fresh track on the resistance plate.
Ron

[narfire]

but I had this issue and it was a bad spot on the resitance track in the AFM.

Ron, how in H...s name did you figure this one out... man are you a go to guy or what.

[rlux4]

Chris, the only credit I can take is having a mind that craves to learn. I decided early on with my FI Spider to learn as much as I could about it and "hit the books". Actually "hit the internet" is mostly where I learned what I know. This tidbit I got here:
http://the944.com/afm.htm
To get a basic understanding of how the system functions I studied Brad Artigue's FI section in his Fiat Maintenance Manual like I was cramming for college finals.
Actually, this is the last thing I did that turned my car from a good running one to one that runs absolutely perfectly.
Ron

[JConnerly]

Problem #1 fixed. Replaced both temp sensors on the head with new ones ( thanks to Mark for the overnight delivery). Temp gauge now reads right on 190 at operating temp. Sigh!
Problem #2: thanks Ron for the link to the article on the AFM. In reading the article and and looking at mine I can see the tracks from the potentiometer and will take a stab at refurbishing it in a day or two. One question, the cover on mine comes off very easily and I could see how it might come loose and allow dirt and moisture to get into it. Should it be sealed with something like silicone?

[So Cal Mark]

use a clear silicone to seal the cover once you get the afm where you want it

[JConnerly]

Finally got around to adjusting the AFM as described in the article in the above link. It made an instant difference in the way the engine cruises at around 2200 RPM. It also seemed accelerate more quickly but that's probably wishful thinking. It's so hard to be objective when the top is down and the exhaust note is singing in your ears.

[rlux4]

Great! Thanks for the update.
Ron

[RRoller123]

This may or not be it, but I had this issue and it was a bad spot on the resitance track in the AFM. I loosened up the set bolt on the sweep arm and pushed it down the shaft ever so slightly and it cleared right up. This sets the sweep arm into contact with a fresh track on the resistance plate.
Ron

Would it be possible for someone to post a photo showing the location of this set bolt? I have the same issue. Thanks.

Pete

[JConnerly]

Click on the link in Ron's posting above. It will take you right to it. It has very clear photos and instructions.

[rlux4]

Did you go to the link I gave for AFM repair? It shows the bolt a lot better than any of the pictures I have. The author calls moving the sweep arm either "north" or "south". What he means is up or down.
Ron

PS; just saw the post by JConnerly. But I thought I'd add the bit about the direction anyway.
And you're right J, my pictures of the open AFM don't show the detail anywhere near as clear.

[RRoller123]

Thanks, I got it. Is this the bolt they are talking about?

Looks like moving the wiper down flexes the arm a little, pushing the contact point further out on the ceramic.

[JConnerly]

That's the one. I just pushed it down about a 16th on an inch. Still running much smoother than it was before the adjustment.

[RRoller123]

Pissah. Thanks, I will give it a try.