How does the AFM screw works? - Alfa Romeo Forum
You are currently unregistered, register for more features.    
 7Likes
  • 1 Post By BigAl33
  • 1 Post By BigAl33
  • 1 Post By BigAl33
  • 1 Post By BigAl33
  • 1 Post By BigAl33
  • 1 Post By BigAl33
  • 1 Post By BigAl33
 
Thread Tools Search this Thread
(Post Link) post #1 of 20 Old 24-08-16 Thread Starter
Status: -
AO Member
 
Join Date: Jan 2010
Location: Portugal
County: Coimbra
How does the AFM screw works?

Hi

On the process of trying to start my 1.7 16V I turned the tune screw of the AFM.
I did not turn if 1 or 2 turns, but A LOT of turns and I tried both sides.
So now I dont know how to solve this...
I know by this site that if we turn the screw clockwise will rich mixture, if anti clockwise will lean it.
So far so good... or not.
The problem is that at some time I think did some 50 turns!!!... so as you can understand Im lost!

The AFM has an endless screw and because of that I can not say if Im at the begining of the scale or at the end of it...

How does it work internaly? (the screw mechanism)

How is it possible to tune te car (on the AFM screw) without a gas analyzer.

Yesterday I tryed to lean it (anti clockwise lots of turns) and no diference on the engine...

Thanks

Last edited by gralalfafan; 24-08-16 at 14:50.
gralalfafan is offline  
Sponsored Links
Advertisement
 
Status: -
AO Silver Member
 
BigAl33's Avatar
 
Join Date: Feb 2006
Location: U.K Surrey
Images: 4
The manual says if changing an ECU or AFM then you need to set idle with lambda disconnected.
voltage on pin 1 on the AFM fluctuates between 0V and 5V when you rotate the CO adjustment screw, set it to 2.5v as a starting point

Does your car have a lambda sensor? If so, disconnect the black wire and take measurements from it. (leave the 2 white heating wires connected) aim for about 0.45v
gralalfafan likes this.

Last edited by BigAl33; 24-08-16 at 21:14.
BigAl33 is offline  
(Post Link) post #3 of 20 Old 24-08-16 Thread Starter
Status: -
AO Member
 
Join Date: Jan 2010
Location: Portugal
County: Coimbra
Thanks for your reply.

My car is from 1991 and has no cat and no lambda probe, 137cv version

Quote:
voltage on pin 1 on the AFM fluctuates between 0V and 5V when you rotate the CO adjustment screw
What is pin 1?
The one counting from the left to the right?


Quote:
set it to 2.5v as a starting point

And thats it???
Have to turn as mutch turns it needs to have 2.5V?
Measure it between pin 1 and negative from battery?
gralalfafan is offline  
Status: -
AO Silver Member
 
BigAl33's Avatar
 
Join Date: Feb 2006
Location: U.K Surrey
Images: 4
If you take the wiring loom plug off the AFM and look at the AFM you will see pin 1 numbered, you may need good vision or a magnifying glass.
Without a lambda sensor you will need a gas analyser

The idle mixture screw is like a long grub screw on a variable resistor track, adjusting the voltage between 0 and 5 volts. When you get to the end of the track either way, turning it further makes no difference.
gralalfafan likes this.

Last edited by BigAl33; 24-08-16 at 21:47.
BigAl33 is offline  
(Post Link) post #5 of 20 Old 24-08-16 Thread Starter
Status: -
AO Member
 
Join Date: Jan 2010
Location: Portugal
County: Coimbra
Quote:
Without a lambda sensor you will need a gas analyser
But is the process the same, if I turn the screw searching the 2.5V on pin 1, is it possible it will be near correct tune?
gralalfafan is offline  
Status: -
AO Silver Member
 
BigAl33's Avatar
 
Join Date: Feb 2006
Location: U.K Surrey
Images: 4
No idea its the best you can do without a gas analyser.
Do you know a friendly garage with one that can let you use it?
gralalfafan likes this.
BigAl33 is offline  
(Post Link) post #7 of 20 Old 24-08-16 Thread Starter
Status: -
AO Member
 
Join Date: Jan 2010
Location: Portugal
County: Coimbra
Quote:
No idea its the best you can do without a gas analyser.
Do you know a friendly garage with one that can let you use it?
I dont know anyone with one...

I will try to check the voltage on pin 1, and try to set it to 2.5V.
After that Ill take it to the inspeccion (similar to english MOT) and will try there to tune it.
If its something easy to solve/tune the guys usualy let us solve it and sometimes they help.
gralalfafan is offline  
Status: -
AO Silver Member
 
BigAl33's Avatar
 
Join Date: Feb 2006
Location: U.K Surrey
Images: 4
Sweet, that's all you can do
gralalfafan likes this.
BigAl33 is offline  
(Post Link) post #9 of 20 Old 27-08-16 Thread Starter
Status: -
AO Member
 
Join Date: Jan 2010
Location: Portugal
County: Coimbra
Its done.

When I measured it at first time it showed 0 volts.
I turned the screw until I got 1.96V
After a bit of time tuned it to 2 volts
Lets hope the exaust gases are ok
Thanks for you help.
Attached Images
File Type: jpg IMG_20160827_185950.jpg (117.6 KB, 7 views)
File Type: jpg IMG_20160827_190008.jpg (46.5 KB, 5 views)
File Type: jpg IMG_20160827_190605.jpg (116.0 KB, 6 views)
gralalfafan is offline  
Status: -
AO Silver Member
 
BigAl33's Avatar
 
Join Date: Feb 2006
Location: U.K Surrey
Images: 4
Good luck with the inspection, as I said it's a starting point and will probably need fine tuning to get it right.
gralalfafan likes this.
BigAl33 is offline  
(Post Link) post #11 of 20 Old 05-09-16 Thread Starter
Status: -
AO Member
 
Join Date: Jan 2010
Location: Portugal
County: Coimbra
I took the car to the inspection and I have now a green paper
It was ok, CO was at 2.59 (3.5 is the limit here for non cat cars).
But now I notice that it is pinking a lot!
At 40 its almost normal but you notice its starting pinking...
At 70 its pinking a lot.
At 90 its almost "undriveble" as it pinks almost all the time! (2000, 3000,...)
Something is not right.
No strange smoke, idles fine...
No "popcorn" on the exaust...
What can mess with the advance???
gralalfafan is offline  
Status: -
AO Silver Member
 
BigAl33's Avatar
 
Join Date: Feb 2006
Location: U.K Surrey
Images: 4
Well done gral
why didn't u adjust it to the limit or just under.
check the distributor. take the cap off an when the engine is at tdc make sure the rotor arm is pointing to the line on the main body of the distributor.

http://www.alfa-pages.co.uk/viewtopi...ributor+timing
BigAl33 is offline  
(Post Link) post #13 of 20 Old 05-09-16 Thread Starter
Status: -
AO Member
 
Join Date: Jan 2010
Location: Portugal
County: Coimbra
Quote:
why didn't u adjust it to the limit or just under.
I didnt touch it because I think I read somewhere that the correct value was 1.5, and so I let it be in the middle (1.5 - 3.5)

Quote:
check the distributor. take the cap off an when the engine is at tdc make sure the rotor arm is pointing to the line on the main body of the distributor.
Ok...
Ill do that tomorow.
I thought that it was not important because I always read that the ECU would deal with it, that it only would have to be near...
Is that important?
Can it be the reason of pinking a lot?
gralalfafan is offline  
Status: -
AO Silver Member
 
BigAl33's Avatar
 
Join Date: Feb 2006
Location: U.K Surrey
Images: 4
ahhh ok.
yes, read my post on the subject lol.
didn't seem to make much difference for me.
what fuel are you using.
in the u.k cars with no cat and no lambda correction use 97 ron ignition advance map, someone may correct me if i'm wrong.
does your wiring loom have a fuel selector dongle type plug, probably doesn't, if so there should be nothing in it, colours are, blue, yellow, red.
BigAl33 is offline  
(Post Link) post #15 of 20 Old 05-09-16 Thread Starter
Status: -
AO Member
 
Join Date: Jan 2010
Location: Portugal
County: Coimbra
Im using 95ron.
You are right non cat cars should user 97/98 ron fuel, but even before it broke I used 95 ron without a problem.
My wiring loom doesnt have any dongle.
gralalfafan is offline  
Status: -
AO Silver Member
 
BigAl33's Avatar
 
Join Date: Feb 2006
Location: U.K Surrey
Images: 4
when were the spark plugs done?
weak spark?
only things I can think of would cause bad emissions, so no point in going through them.
anyone else want to chime in?
you could try the blink test, check for error codes.
http://www.alfa-pages.co.uk/ml41sd.php

any mods to the car? 5 min AFM mod?
BigAl33 is offline  
(Post Link) post #17 of 20 Old 05-09-16 Thread Starter
Status: -
AO Member
 
Join Date: Jan 2010
Location: Portugal
County: Coimbra
No mods on the car.

What is the 5m AFM mod???

The spark plugs are the ones that were in the engine before it broke, they have many years but not mutch Kms, the car was not working for about 8 years.
gralalfafan is offline  
Status: -
AO Silver Member
 
BigAl33's Avatar
 
Join Date: Feb 2006
Location: U.K Surrey
Images: 4
cool, that makes it easier to diagnose for someone who knows more than I.
the 5 min AFM mod is done to adjust the mixture by moving the flap spring to a different position, making it weaker, allows the flap to move further therefore a weaker mixture as more air is coming in but the ecu thinks the air amount is normal... vive versa. don't bother as this will effect emissions.

Fuel looses about 1 ron per year, maybe you need to wait until all the fuel has been used and then use 98 ron.

ADMIN
why did my post, which had a relevant link to another forum, get removed, if that's the way its going to be I wont bother posting here anymore
gralalfafan likes this.

Alfa 33 16v

Click the link below to see what I'm doing to raise money for cancer research
http://myprojects.cancerresearchuk.o...es/mrt-mohican
BigAl33 is offline  
(Post Link) post #19 of 20 Old 07-09-16 Thread Starter
Status: -
AO Member
 
Join Date: Jan 2010
Location: Portugal
County: Coimbra
I think I found the problem...

Two problems!!!

The old fuel and a f#ck$ng radiator full of clay!

I put about 13 liters of 98ron and it got a lot better, but part of the problem was still there.
But I noticed that the car was working very hot, most of the time near 100, and few times past it (a little)
I replaced the original radiator with an old one from a normal 33, the temp is now normal 80s when driving, and now it pinks the normal...

I have to order a new rad, this one is old and came from a series 2 car that I had for parts, its all metal, (no plastic parts on the side) and in the meddle it is copper.
gralalfafan is offline  
Status: -
AO Silver Member
 
BigAl33's Avatar
 
Join Date: Feb 2006
Location: U.K Surrey
Images: 4
Well done Gral,
You got there in the end
gralalfafan likes this.
BigAl33 is offline  
Reply

Go Back   Alfa Romeo Forum > Supported Alfa Romeo Models > Technical & Vehicle Assistance > Alfa 33, Sud & Sprint

Tags
afm , screw , works

Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome