Afm Flap - How 'springy' Sould It Be

[GLPoomobile 958]

Before you all start whinging, I know this has been discussed before, and I have done a search. I don't have a decent answer yet though, and this may benefit new members who have never even given the subject any thought before

 

Some of you may have read that I had a spot of bother with the Mi in the last couple of days. I eventually tracked this down to a buggered AFM. The flap was stuck wide open causing the engine to overfuel big time at idle.

 

Without playing with the AFM, my immediate response (as per usual, jump in with both feet and a wallet that can't sustain me!) was to post a desperate wanted add for a new AFM.

 

This morning I decided to see if I could fix the AFM. I was convinced the spring was dead as the flap moved reasonably easily but stuck in what ever position I moved it to. However, after a bit of moving it back and forward I started to detect some springiness returning, and with a healthy dose of WD40 and more playing around it now seems to be 95% OK.

 

But, if you open it very slightly and let go it stays in position (talking barely open here). It only tends to swing back if you open it much further, as the spring is under more tension. Works best if mounted flat (correctly) or with the flap hanging down, but in my car it was fitted at a 45 degree angle (plug pointing slightly upwards) so that the front of the AFM would clear the slam panel. At this angle, and with the current tension, I can see that with a little bit of dirt build up it would struggle to close fully after light throttle openings - which is probably why the other weekend my revs were bouncing up and down in stop/start traffic, like a kid with ADHD.

 

So getting to the point (at last ). How springy should the flap be? I know you shouldn't mess with them as it alters the fuelling across the range, that's not my intention. I just want to know if the flap should snap shut quite satisfyingly from any angle, or if it should 'glide' shut, and if it's normal for it not close fully from smaller openings.

 

Somebody pondered in an old thread if the springs would become weaker over time. This makes me think, that since I hear a lot of Mi owners saying their cars smell rich at idle, perhaps they have the same syptoms as mine, and the flap sticking open a little further than it should at idle and causing the mixture to run a little rich.

[Exile 0]

1. The flap should be springy and shut quite agressively.

2. Overfueling can be the effect of dirty/ faulty potentiometer

 

Resistance between pins should rise lineary from 200ohm to about 900-1000 (which pins depends on motronic/jetronic AFM)

by opening the flap. If it's ok, then go to MOT or sth and retension the spring using afr/gas analyser.

[DamirGTI 342]

Hi !

 

Try this (i don't wish to write again so this is my C/P from two or three days ago from another post .. ) :

 

EDIT : or if you loose toothed wheel position try this : remove the securing pin (well i don't know the right word for this in your language but it's a metal ting-wire/pin which blocks/keeps toothed wheel in position) completely then loose the wheel (or spring tension it's a same thing..) a little bit with your fingers until the wiper arm starts to goes/moves anticlockwise , then gently turn/tight the wheel back until wiper arm goes back clockwise to the end/staring point , temporary fit the securing pin and try to locate on which tooth the tip of the pin fits in (which tooth gets in center/in level with the pin tip when you move wiper arm back to the end - clockwise) when you move wiper arm from the middle to the end by turning the wheel , but you must do that very gently ! try a few times to be shuse on which tooth it stops ..

Mark that tooth and then count 18 tooths from that firstly marked one as you tight the toothed wheel/spring tension clockwise and then refit and tight the pin on that ending tooth ..

Well this is not so precise adjustment but I've try/test this on 4 different 1.9 engine AFM-s and they where all setted on the same amount of teethes 17 to 18 from when the wiper arm goes back to the starting point and i measure middle point at the pin tip and toothed wheel teeth..

 

Sorry but this is really difficulty for me to describe , but i hope that you will understand what i mean .. try that just for yourself and see if this idle improves (you can correct it later for fine tuning by turning tooth or two (but don't go more than two tooths on ether side) on the clockwise or anticlockwise side after you find this first starting point which you have loose before by mistake - listen to the engine and try to do/adjust that )

But rolling road is much safer option for that , this is just from my experience, DIY settings and experiments with AFM-s

 

(one more note this works only for 1.9 AFM not for 1.6 item as the 1.6 AFM has different spring tension amount ..)

 

ouch i tooks me 1 hour to write this !!

 

NEW EDIT : on 1.9 AFM-s the spring must be a bit loose , but on the 1.6 AFM-s is a little more tighter (all this references are from my experiments with AFM-s and don't take this so precise ! but this works for me , at least it's close 70% of how much the spring should be tensed ..)

 

Cheers

Damir

[DamirGTI 342]

also ... i have one fully dismantled 205 1.9 AFM i can take a picture of it so that you can see how many parts it has inside if you wish ?

 

if your flap is sticking in some positions (or rubbing on the AFM upper or lower wall..) this can be broken bearing because there are 2 little bearings inside , one bearing up and one bearing down on the flap shaft , theres also one spring one securing ring etc. .....

 

Cheers

Damir

[DamirGTI 342]

again : also if you wish (if you are interested in this things ..) you can read this , I've explane here how can you check/adjust air/fuel ratio by yourself cheap with an digital multimeter and an lambda sensor to see if your car is running lean/rich :

 

http://forum.205gtidrivers.com/index.php?showtopic=77176

 

 

(one note I've been at the MOT yesterday and I've pass without any problems and the guy sad that I've adjusted my engine mixture really good .. using these references all thou my engine is not a standard .. it has high CR , head job etc. .... so you can at least try to do that by yourself (if you have an wideband lambda sensor you can do this mixture adjusting/checking job really very good and precise) , and if you get lost you can always give up and go at the rolling road to set that precisely by professional ..)

 

Damir

[GLPoomobile 958]

I took my original AFM back out to the car this afternoon, and once I'd whippend my borrowed AFM off I compared the two flaps and mine is no where near as springy as the other one. The one I have borrowed snaps shut really quickly and easily, and has plenty of tension. Whereas my own AFM is more like a limp lettuce

 

I put my AFM back on the car just to give it a try and it does run again (as the flap is no longer stuck fully open) but it doesn't want to idle. The revs drop to 500rpm and it either stalls or they bounce up again and you have to try and balance the throttle to keep it idling.

 

I figure I've got nothing to lose so I'll try and re-tension the spring as per Damir's description.

[paulh 0]

Well this is not so precise adjustment but I've try/test this on 4 different 1.9 engine AFM-s and they where all setted on the same amount of teethes 17 to 18 from when the wiper arm goes back to the starting point and i measure middle point at the pin tip and toothed wheel teeth..

 

Damir

Have you any idea how many teeth adjustment you need on a 1.6 AFM. Mine has been messed with and could do with a starting point.

Thanks

[DamirGTI 342]

I took my original AFM back out to the car this afternoon, and once I'd whippend my borrowed AFM off I compared the two flaps and mine is no where near as springy as the other one. The one I have borrowed snaps shut really quickly and easily, and has plenty of tension. Whereas my own AFM is more like a limp lettuce

 

I put my AFM back on the car just to give it a try and it does run again (as the flap is no longer stuck fully open) but it doesn't want to idle. The revs drop to 500rpm and it either stalls or they bounce up again and you have to try and balance the throttle to keep it idling.

 

I figure I've got nothing to lose so I'll try and re-tension the spring as per Damir's description.

 

Hello !

 

Try adjust idle like this : http://autospeed.drive.com.au/cms/article.html?&A=2055 and then (if you don't have a lambda sensor buy one narrow band sensor with 4 wires (these ones haves heater so they don't need to be fitted close to the engine) , or wideband sensor if this is not too much for your budget .. you have description how to adjust AFM spring for good stable idle in this article above , and also how to mount lambda sensor in the exhaust pipe .. but i found this better fitted in the middle of the exhaust pipe just before the center muffer ..) connect a digital multimeter (try to buy a good quality one ..) on the sensor signal wires .

After you've adjust the AFM spring tension for good idle , switch on the multimeter (turn it on 20 DC ..) and go for a ride but you must wait/drive at least 20min. until the sensor tip heats fully and then he will give correct volt readings . Observe the multimeter voltage as you accelerate from the mid to high revs (don't bother too much about low and mid range voltages below 300rmp's , high rev voltages are most important and that you must look at) , the voltage must rise rapidly as you pres the pedal fully from mid revs to high (for example start from 3000-4000rmp and then you pres pedal fully and voltage must rise , well lets say from 0.80-0.82mv on 3000rmp as you accelerate that this rises like this : 0.80-0.82-0.85-0.88mv as the revs rises to fully 6000rmp, and this will depend on how hard you pres the pedal if you press/snap the throttle really hard it can also jump faster from 0.80-0.82mv straight to 0.88mv and stays in this area to fully 6000rmp which will indicate that your mixture is good .. well it can be a little richer but no way that it's lean if you see 0.85-0.88mv at the multimeter on 6000rmp it can be as high as 0.90mv on full throttle but this is a bit rich , it's good for power but not good for the fuel consumption )

You need 0.86-0.88 at full load and around 0.82-0.85 at mid range (4000rmp) , try that and adjust the AFM spring tension until you get similar readings , but not too much tooths at once , go on tooth at the time and then go for a ride write the readings and if it's not enough stop go one tooth more and go for a ride again and check voltage etc. .... also if the exhaust is popping or surging on over-run whey you let of the throttle this will also indicate to you that your mixture is too lean , but voltage readings will be good diagnose lean mixture ( anything below 0.80mv on the full load is not good - too lean , also anything below 0.70 on mid range is too lean and if you see voltage from 0.60-0.70 on mid range you will also hear exhaust popping and surging on over-run as i sad before ..)

In between this adjustments check for plugs color they must be coffee tan to rust brown (if they are shinny white this is dangerous : lean running plug - lean mixture..) for the best mixture , if the plugs are black or if you see tiny dry/or whet black specks/spots on the plugs which can you easy rub of wihte your fingers this will indicate to you rich running plug - rich mixture ..

After this adjust CO at idle with the AFM mixture screw (when you make good mixture on high revs and good/stable idle)

If your idle becomes bad (start to swing up and down badly) when you finish adjusting good mixture on high revs just back off the spring tension for one tooth back and unscrew the AFM mixture screw a little bit out (one or half turn out ..) I'm sure that it will be fine on idle (you can go 2 tooths back , but i can advice you that you don't go more that two for idle settings..)and will not harm too much on your's previous adjusting for high revs ..

Also you will feel that exhaust smells different/good when you adjust good idle mixture ..

 

Sorry but i didn't ask you is your 205 with mi16 engine or ? if so it has different AFM so this previous explanation on finding initial toothed wheel position will not worth on mi16 AFM , or maybe it will i don't know ?!

This my explanations was for 1.9 AFM-s but from 8v engines not the 1.9 16v (mi16) ...

 

Anyway you should be able to adjust this yours mi16 AFM as i described now with an multimeter and lambda sensor .. and the exhaust CO analyzer for the end settings of the idle mixture (you can go at the MOT and ask them to help you with checking/adjusting CO at idle if you don't have (or can't borrow this tester form somebody , you're mate or local mechanic guys ..) an exhaust gas analyzer ..)

 

hope this helps !

Damir

[DamirGTI 342]

Damir

Have you any idea how many teeth adjustment you need on a 1.6 AFM. Mine has been messed with and could do with a starting point.

Thanks

 

 

No sorry my engine is 1.9 so i didn't experiment with 1.6 AFM-s , i have just one 1.6 AFM but it was from not knowing previous car from a scrappy , so i don't know if it's ever been adjusted on rolling road and i don't have other 1.6 AFM (correctly adjusted) to compare these two and look for the differences on toothed wheel initial positions .. sorry !

 

But you can use this references above that I've just been described to our colleague GLPoomobile - buy an sensor , multimeter etc. ...

 

Kind regards !

Damir

[DamirGTI 342]

Some pics of fully dismantled 205 1.9 8v AFM :

 

http://i27.photobucket.com/albums/c151/Pie...is/IMG_5380.jpg

http://i27.photobucket.com/albums/c151/Pie...is/IMG_5381.jpg

http://i27.photobucket.com/albums/c151/Pie...is/IMG_5382.jpg

http://i27.photobucket.com/albums/c151/Pie...s/rrr43copy.jpg

 

And this is interesting - one example of badly damaged carbon track , but strangely enough it still works if very carefully/precisely retracked :

 

http://i27.photobucket.com/albums/c151/Pie...is/IMG_5384.jpg

http://i27.photobucket.com/albums/c151/Pie...is/IMG_5387.jpg

 

Cheers

Damir

[GLPoomobile 958]

I tensioned my spring up as per the description - released the V shaped clip, moved the toothed wheel anti clockwise until the flap opened, then slowly moved it clockwise again until the flap was just closed, then moved the wheel by 18 teeth and put the clip back in position.

 

I haven't tested it on the car yet, but I have a feeling it will be no good

 

When I compared it to the other AFM that I borrowed, my AFM now has too much tension. The flap is obviously much stronger on mine now, so the fueling will be no where near correct.

 

So this method might work on a 1.9 8v AFM, but not an Mi16.

 

On a positive note, it's a piece of cake to adjust, so putting it on a rolling road and making adjustments shouldnt be too much of a chore