Fuel Mixtures - Mark
I think my cars running a slightly rich mix (spark plugs were fairly black when I changed them) so... I know where to change the mixture but which way do I turn it?! Is in more fuel/richer mix or is out?

The car's an '88 Audi 80 1.8 carb. I think the model of the carb is a Kleihn II or something similar to that.

I know it's a bit tight fisted but I resent paying somebody to turn a screw!

Thanks in advance,
Re: Fuel Mixtures - David Lacey
The CO% adjsuting screw is usually located near to the base of the carburettor (They have a habit of hiding them!) Turning the screw out (usually) allows more air to bleed past the taper of the screw therefore weakening the fuel/air mix. The only real way to do this adjustment is to pay somebody with the correct equipment. If you do get it wrong, you are leaving yourself wide open to roadside emission test failure, meaning you will be forced into a full MOT test even if your car has 8 months left. Be warned.
Re: Fuel Mixtures - Adam Going (Tune-Up Ltd0
Sorry, but I think you have got this one a bit back to front!! Turning the mixture (or volume) screw anti-clockwise / out allows more FUEL past the end of the taper, thus richening the mixture. Perhaps you have seen the mixture lean off after turning the air-bleed (idle SPEED) screw out to raise the idle speed - this does have the effcet of slightly weakening the mixture. Usually the mixture scerw is smaller than the air-bleed / speed screw, both normally being located close together.
As others have said, it is easy to end up outside emission limits without correctly calibrated test equipment, and anyway, emissions are influenced by a lot more than just the mixture screw. Personally, if someone asks me "just" to adjust their carb I say no, as it is literally the last thing to be done during a comprehesive tune-up, after all the other areas have been checked/adjusted.
Regards, Adam
Re: Fuel Mixtures - D J Woollard
You're not just paying for a turn of the screw. The emissions testing equipment used may cost thousands and the guy will get it spot on. Take it to an MOT station and just ask for this test/adjustment. After all if some guys are doing a whole MOT for £20 you might get away with £5 - £10. Well worth it.
If you really can't stomach the thought of paying others to do this go to Halfords, buy a Haynes manual for £12.99 and a Gunsons CO tester for about £75. Then you can do it yourself.
Re: Fuel Mixtures - Mark
Yes, you're right. I should get it done properly. The MoT's due in about 2 months anyway so perhaps I'll just get it done early this year.
Re: Fuel Mixtures - Cliff Pope
If you have a friendly MOT man just mention it to him in advance and he will probably give the screw a tweak as he tests the CO2 and it will cost nothing. Mine did.
In my experience MOTers are well worth cultivating.
Re: Fuel Mixtures - Andrew Moorey (Tune-Up Ltd.)
Not telling!!!!!!!!
Clockwise to weaken,Anticlock to richen. Oh if it was only that simple!!!
Hang on guys! - John Slaughter
Hang on guys! Before you start tweaking the carb., or paying someone else to tweak it, you need to ensure it is the cause of the rich mixture. Plug colour can only be gauged after the engine has been allowed to warm up fully and preferably checked only immediately after a long fast run. Then make sure the plugs are the correct grade, that the timing is correct, that the float level in the carb. is correct, that the float valve isn't worn and that the air cleaner isn't blocked. Only then assume it's the carb. setting. Otherwise you're trying to compensate for faults, rather than correcting them!


Re: Hang on guys! - Adam Going (Tune-Up Ltd0
Beat me to it by minutes Andrew !!

Re: Hang on guys! - Adam Going (Tune-Up Ltd0
SORRY !! Beat me to it by minutes JOHN !

The end of a long day !

Re: Hang on guys! - Mark
Ok, now you've uncovered my ignorance re: engine tuning I'll get the yellow pages out.

Re: Hang on guys! - Guy Lacey
Alright Tune-Up boys - calm down and get on with some work - remember what that is? You must have a load of people doing the work for you or no work at all.

Anyway - I *love* it when someone gets one up on my "all-knowing" brother Dave. No wonder my 850 Mini never ran right.

Keep it up!

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