Which Screw is the Air/Fuel Mixture?

MeatProduct

For various reasons I'm getting the impression that the air/fuel mixture is way out on my car (Mitsubishi Mirage 1994 1.3 auto). To that end I've been given the advice to turn air/fuel mixture screw 1/2 in to see if that makes a difference. However there are 2 screws on the carb and I don't know which one to turn, 1 is the idle and the other is the mixture?




Any advice greatly appreciated

Thank you,

Nick

greglo23

its screw B. the problem with those is they are a tamper-proof system so you may have to break off the plastic surround to get at the fuel screw unless you have the special bits to adjust it. clockwise makes the mixture leaner so adjust in the screw until the engine begins to run roughly and then come back out a bit . you will see the difference as the mixture changes. an old trick was put a cup of water on the engine and try to get it as still as possible which meant gave you the optimum mixture.

MeatProduct

greglo23 wrote:

its screw B. the problem with those is they are a tamper-proof system so you may have to break off the plastic surround to get at the fuel screw unless you have the special bits to adjust it. clockwise makes the mixture leaner so adjust in the screw until the engine begins to run roughly and then come back out a bit . you will see the difference as the mixture changes. an old trick was put a cup of water on the engine and try to get it as still as possible which meant gave you the optimum mixture.

That's great Greglo, thanks very much for that. I'll have a go of breaking off the plastic bit, was wondering about that. It does shake a lot so I'll aim for the stillness

Thank you very very much.

Nick

kluivert

Do multi point injection cars have something similiar, my engine shakes and ticks and I was wondering maybe the fueling is rich because I have to drive very ecomoncial to get 40mpg. Normally check 36-38 mpg.

1999 1.4 Astra

greglo23

id say you've got a dirty throttle body / stuck butterfly which is pretty easy to sort with a bit of spray fuel injector cleaner and a clean cloth.

AMurphy

kluivert wrote:

Do multi point injection cars have something similiar, my engine shakes and ticks and I was wondering maybe the fueling is rich because I have to drive very ecomoncial to get 40mpg. Normally check 36-38 mpg.

1999 1.4 Astra

May have depending on EFI system.

Start with the throttle cleaning as above.
Then take some pix of your throttle body see if we can locate idle adj screws on it.
also insure the ignition system is OK, and times properly, if adjustable.

Some have manual adjust, some have auto adjust/fast idle/choke, which you cannot adjust, without also adjusting the brain of the system.

mike65

As a rule tweaking the air/fuel mix without an exhaust gas probe is so hit and miss as to be a waste of time.

Mike.