AFM setting, and cutting out 1.6 CTi

[lagonda 41]

Chuffed after months of work to have the CTi pass its Controle Technique first time. The CO reading this time round was 0.47%, which sounds rather too lean to me. January 2022 the reading was 1.55%, but they may have been wth my other AFM fitted. What CO reading is considered ideal? How many turns/degrees turning the AFM adjusting screw to get to that "ideal" reading from where it is now?!

 

My CTi now has a new petrol pump and spark plugs fitted. The tachymetric relay I'm pretty sure is fine. Swapping the coil, ignition amplifier, AFM, and distributor, and cap, and rotor arm, and signal lead all have had no impact on it cutting out. It tends to cut out once it's hot, and it happens more at low rpm than higher. Sometimes it'll cut out for several seconds ... which enables me to see it isn't cutting out totally, but temporarily sticking at idle. On those occasions, pumping the pedal will eventually encourage it to behave.

 

Observations/advice please!

[Tom Fenton 1,536]

If it runs nicely leave it alone is my advice. The adjustment on the air flow meter only really adjusts the idle mixture and not the rest of the rev range as it is just an air bleed bypass around the air flow meter flap to fine tune the idle mixture.

 

The cutting out for seconds at a time, or really just becoming unresponsive but still running, in my experience is the air flow meter at fault.

[lagonda 41]

Hi Tom ... OK, but if that's the case then both the original and my spare AFM have the same fault ... is that likely?

 

I took some cakes round to the garagiste that pressed out my worn wheel bearing, and mentioned electrical problem to him. He immediately stated he felt it was more likely a fuelling issue. Just fitted a new Bosch pump, so that leaves filter and pressure regulator. The injectors have been cleaned a few years ago. I changed the filter a few years before that and doubt it needs changing. Which just leaves the regulator. Could that be a likely culprit?

[welshpug 1,644]

I doubt it but it's not difficult to test, stuff is getting old now.

 

get an inline pressure gauge fitted, if present don't cut the original fuel lines to fit it as they are a nylon line sleeved with rubber, very long lasting and don't come off the fitting without damage.

[petert 577]

Sounds like it’s too lean on the idle circuit. Is the mixture screw blanked off, like on DFZ engines? If so, remove the tamper proof plug and have a fiddle.