Cis issues

[76targauk]

Hi

I seem to be having an issue with my 762.7 CIS, My car takes a few cranks to start then is rubbish untill i rev it over 2000rpm

However once warm it seems to be fine but takes a while.

If i help the venturi just by lifting it 1mm it picks up the revs fine??

How can I adjust this, is the mixture??? Whats the issue??

Many Thanks

Scott

[Paulporsche]

Hi

If you use the search function, you will see there is a lot of time spent on this. If you are lucky it may be merely that your mixture is a little lean. This can be corrected by turning the screw down in the mixture control unit in a clockwise direction in small (1/32 or 1/16 turn increments). This is the simplest/cheapest item to check and fix.

There may be other issues however. You should search info on the AAR and WUR, both of which come into play during start and warmup. The WUR continues on working throughout the entire temp range. Often these go out of adjustment and need to be reset or replaced.

[76targauk]

Hi,

How do you know what setting the mixture should be, so I need a gas analyser


Scott

[Paulporsche]

I can't tell where you are located, but if you don't need to pass a smog test, the recommended CO is 3.5% (per JW).

Without a meter, you can still get a good setting, even though you don't know the exact figure by raising the sensor plate in the mixture control unit while @ warm idle, which it sounds like you have done. If the revs rise you can go richer. If lowering the plate makes the revs rise you can go leaner. If you raise the plate and if you lower the plate and the revs fall then you are OK.

If, after warmed up, you get a fluctuating idle you are too rich. Set the mixture back a little leaner. If you get any popoff valve popping, you need to enrichen.

If, after this, you are still having warmup idle problems, you need to check your WUR and AAR.

[Nitrometano]

What is the AAR?

[clevy70911T]

Aux Air Regulator, pass side engine down near injectors.

number 36


www.pelicanparts.com/911/911_Parts/1978-83/1-7-2.JPG

[76targauk]

HI,

How Can you reset the WUR

[Paulporsche]

Searching will yield the various techniques and procedures for "knocking the plug" and for making the WUR infinitely adjustable.

[Nitrometano]

What can cause an high idle (4,000 rpm) at the start up when the engine is cold?

[clevy70911T]

My aux air valve was bring it up to about 2000 rpm, so I plugged it and then I'm down to 1000 warm, but after driving awhile it rose to 1300. My AAR is closed now and I have no air leaks and my throttle plate/ idle screw is closed also. I might have to see if the decel valve is still allowing air to pass. To check them I occluded them with a duct tape diaphram and stuck the hoses back on to see where my idle was. In the a.m. I will start again and see where my cold idle is with my new setup. I think I knock the plug alittle too far so cold morning starts will require a slight warm up time. Still much better than before.

[Nitrometano]

what is the decel valve?