AFM Factory setting?

[Qberto]

Hey guys, been driving my '82 Fiat around lately but had some issues, one a little frightening while on the interstate.

The back story... (skip down to TL;DR near the bottom for the actual issue and question, please.)

I first had some issues with the Idle and starting. The idle was inconsistent. At time it would be around 1300 rpm, other times 600 rpm. The starting (specifically cold starting) issues have been persistent since i bought the thing. This is even after changing the CC injector and temp sensor(?, the one thats wayyyyy towards the bottom of the motor). So i figured that i'd take a look at the AFM. I have never seen or messed with one before so i thought that i'd take the top black cover off and have a look-see. After checking it out for a little bit i began to move the arm around to open and close the flap. To my surprise there was a rough spot in the travel. I began to think that this rough spot was causing the flap to stick a little open one moment and closed the other. For example, if i gave it a lot of throttle and quickly let off, the idle would be really low. Conversely, if i were to give it a lot of throttle and eased off the throttle slowly it would idle rather high. This made sense. So i took the AFM off the car and tore it apart to get to the bottom of it. It looked like something got in there at one time and banged around. There were little kicks here and there and even the butterfly was cracked. After taking sandpaper on a few spots i got the flap to open and close nice and smooth

Back on the engine it went.

Upon putting it back on i noticed that the teeth on the AFM black gear had a red mark. But it was wayyyy away from that W looking spring. "No matter" i thought, "I'd just put everything on as it was before" Lo' and behold the idle was consistent and smooth.

I stepped back and admired my newfound accomplishment. "No more weird idling and odd stop-and-go situations. But wouldn't it be nice if i fixed the start issues too?" This got be thinking, which normally leads me to unnecessary frustrations. Alas, i continued.

That red mark on the AFM gear seemed out of place and one of the previous owners must have messed with it. There was a zip-tie holding the back cover on the top, and i know that it didn't come from the factory like that. So i played with the AFM arm a little. I would start the engine, it would start to have difficulties, i then would swoop out of the driver's seat and zip right over to the AFM and move the arm around. If i left it alone, the engine would rough idle at first initially after the start, but when i opened the flap a little it would idle perfect. Once the engine warmed up however that very same spot holding the arm it didn't want to idle but instead preferred to idle where the flap would be relaxed.

So i figured maybe the spring was too tight. After all , the red mark on the black teeth was prob a half a rotation away from the W thing. So before i played with moving it around i marked it where it currently was and rotated the teeth a half a turn counter clockwise, softening the spring to make it easier to get in that sweet spot i found when i manually moved it around with my finger. I hear 4 clicks is enough to mess with the AFM, but this half a turn was substantially more than that! I have no idea, but it was a lot. At the red mark the spring was JUST strong enough to close the flap all the way. (One click more counter clockwise and it wouldn't close all the way without me nudging it a little with my finger slightly.)

Once set i got back in the driver's seat and cranked over the engine. It hesitated at first but then went right back up to idle without me having to constantly rev the hell out of it for 15 - 30 seconds like it used to. Seems okay so far. On a side note, last year when i took the spark plugs out they were VERY lean, so i figured that softening the spring would help richen it up too.

So thats where i'm at right now. I'll try tomorrow on a true Cold Start so see how things go and drive it around for a while, weather pending.



>>> TL;DR <<<
After fixing something on the car, i took a swing that maybe the AFM was causing some other issues. It seems ok for now. However, since it seems that previous owners may have already messed with it, i took an educated guess at its original settings. Is there anyway i can find out how to properly position the black gear that tightens and softens the spring on the AFM??? Thoughts? Suggestions?

Thanks and Happy Motoring!



-Matt

[joelittel]

This guy seems to know the L-Jet quite well.
http://www.hiperformancestore.com/ljetronic.htm

Someone here on the forum recently posted that they sent their AFM to a specialist shop and had it set back to factory spec. I don't recall the name of the shop, but a little searching through recent posts (within the last year) and I'm sure you'll find it.

Even if you were able to get your spring back to it's intended position, it may no longer have enough strength to control the flap the way Bosch intended it to.

Maybe http://www.midwest-bayless.com/?gclid=C ... gQodsZoM0Q or http://www.spiderroadster.com/ could help you with finding the spring.

[ORFORD2004]

https://www.youtube.com/watch?v=yQukm7lNux4

[RRoller123]

That is a great video! But the 18AWG wire will definitely effect the spring tension as the arm rotates, even with it being formed to a conforming curve. A 22AWG or similar very light wire would make more sense.

[Qberto]

* UPDATE *

Thanks guys for the video and references. I reviewed them both and seem to parallel with what i was doing and had in mind. I will think about sending the AFM to someone to set it back to normal if that time comes.

I tried to start it up again this afternoon with a true Cold Start vs last night's warm start. It behaved the same way whether it was cold or hot, which is good. It used to be a pain to get it idling and not dying, sudden spike in RPMs, and me having to baby the throttle until it got warm. Its much much better now. A little slow to get the RPM's up to 900, but as the seconds it takes to get warmer the idle starts coming up to 900, every time.

Very happy with the results so far. I'll try to drive it around for a bit later and check the spark plugs to see how they look compared to how they were last year. Last year they were very lean, chalk white. I"m hoping to see more color in them. Im also hoping i can prob adjust the black teeth in the AFM to get the right amount of mixer via examining the spark plugs.

[RRoller123]

Once warm, the O2 sensor (if good) should put out an average of 0.4 Vdc. It will jump around, but with a digital multimeter you can see if the mixture is far off or not.

Someone correct me if I am wrong about the 0.4Vdc, but I believe that is the correct figure.

[Qberto]

* UPDATE 2 *

Awesome.

Although i have not checked the O2 sensor yet i can tell there is a big difference already, much smoother off turns while getting on the throttle. Over all power is substantially better. The black teeth on the gear must have been WAY off when i bought it all this time. I deff noticed a power difference and i wasn't even really trying to feel a difference initially. Theres a road near my house thats pretty secluded and about 1.5 miles of straight road. Normally when i get on the road and floor the throttle i can only get to about 75ish by the time i had to slow down for the turn/stop sign. Today i was only just past half way and was already going 70ish before i had to slow down for a car that was coming towards me. Could have done a U-turn and see what speed i could get it up to but that was good enough for me to believe there was a difference.

Haven't checked the spark plugs or the O2 sensor yet for its voltage (ill do that sometime this week) but it was a huge step in the right direction. I'll fine tune it later in the week.

Very Happy