Idle mixture on 1.8 M40 MAF
Moderator: martauto
Ok, now I've got my vacuum leak fixed, I need to get the idle mixture adjusted. The guy at the MOT testing station tried to adjust it the other day, but couldnt because of the vacuum leak. I've just had a look at the brass flat head screw under the red cap on the maf, and it just turns and turns, and doesnt seem to hit a stop. Is this normal?
1. This is not an idle adjustment as there is no idle adjustment on the M40.
2. It's not a MAF (Mass air flow), it's afm (Air flow metre).
3. I hope you remembered how many time's you turned it cos' you need to put it back to the same place. You are either running too Lean or VERY rich now after adjusting this.
4. If the afm has not been tampered with before hand then it was the air leak that was causing any problem's and was probably fine.
All you have done my friend is cause another problem after fixing the other
Never mind, at least it ain't broke
2. It's not a MAF (Mass air flow), it's afm (Air flow metre).
3. I hope you remembered how many time's you turned it cos' you need to put it back to the same place. You are either running too Lean or VERY rich now after adjusting this.
4. If the afm has not been tampered with before hand then it was the air leak that was causing any problem's and was probably fine.
All you have done my friend is cause another problem after fixing the other
Never mind, at least it ain't broke
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smithy318i
- Engaged to the E30 Zone
- Posts: 5797
- Joined: Thu Apr 28, 2005 11:00 pm
- Location: Tyne & Wear
im waiting for someone to reply too. 
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Brianmoooore
- E30 Zone Team Member
- Posts: 49358
- Joined: Mon Jan 10, 2005 11:00 pm
Never really thought about it in terms of weakening or richening the moixture, as it just needs to be tweaked to get the correct reading on a CO meter (0.7% @ 3000RPM for an M40), but logically, anticlockwise opens up the air bypass, less air flows past the flap meter, so less fuel is injected. I.E. Anticlockwise weakens the mixture.
You need to make sure there is no air leak's anymore and get it back on the CO meter mate. The reading's for idle are 1.2% to 1.5% but 1.2 is too weak but the MOT bloke will tell you that's how it should be. Try to put it around 1.3 to 1.4 and it should be alright.
Let me know how you get on and see how she is from there
Let me know how you get on and see how she is from there
OK just to update, I didnt get round to having the mixture looked at because the car has been running so well, and the plugs look great. However, today I took the car for the MOT, and yep you guessed it, it failed on High CO 
The reading for CO was 5.165, and should be less than 3.5 to pass the MOT (I know it should be 1.3-1.4 to be ideal). I've got it booked in for Thursday to have it setup properly.
The reading for CO was 5.165, and should be less than 3.5 to pass the MOT (I know it should be 1.3-1.4 to be ideal). I've got it booked in for Thursday to have it setup properly.