Adjust Mixture now that I have the tool?

[bagpiper47]

My 1981 SC mixture adjust tool just arrived from my monthly shipment from Pelican, along with a Fan Belt (Just in case) and the only tool missing from the original tool kit the (fanpulley holder wrench Just in case again).
My question is should I adjust the richness as it seems when my clutch and airbox were installed in JanuaryI watched the mechanic adjust it right before I got it back and it doesn't seem to have quite the power it had before. I dont have the analyizer but would like to try a few clicks richer. Will this hurt anything? How many clicks should I turn it? Recent tune up in November
had it running great. The new fuel accumulator I put in stopped the warm start issue but I wonder if a new fuel pump is on the agenda (it hums and both cold and warm start takes about 3-4 seconds) it used to start right up. Anyway back to the richness issue. OK to give it a try?

Sorry about the ramblings. New to DIY

[Paulporsche]

If you have been reading any of the many past threads on this, then you know that these cars run pretty well within a wide range of CO settings, from under .5% up to over 3.5%. Obviously you can't know exactly what your setting is w/o the analyzer. However, you can tell some basics about where you are through some typical symptoms. For example, if your engine backfires under acceleration you are set too lean. If the revs hunt @ idle, you are set too rich.

You can try to richen the mixture by turning the screw clockwise (as seen from above) and seeing if you still get a steady idle. If so, then you will probably be able to take advantage of the greater power and lower temps that you get from the richer setting. Keep in mind how much you turn the screw and, if you get hunting, turn it back just a little.

By the way, they don't always click, in which case you should limit your adjustments to as small an increment as you can discern. Also, I am assuming all other aspects of the car are running correctly, eg no vacuum leaks, WUR control pressures correct, distrib and timing correct, etc.

[strupgolf]

Paulporsche, where is the adjustment screw for the idle mixture?. Newbie here, and my car does hunt for a good idle upon startup, then settles down later. But Im still getting a rich condition, smell, etc. Thanks

[stlrj]

where is the adjustment screw for the idle mixture?

There is a small hole located between the air boot and the fuel distibutor. Run your allen along that area and it should fall right in.

-Joe

[kstylianos]

From a previous post:

The following needs to be done with the engine warm so the WUR and other CIS components are not compensating for cold enrichment.

"I found that every CIS engine has its particular 'happy place' where it likes to run. No two are exactly the same but CO% usually falls between 2-3.5%.

This can be set by ear and its very acurate for best performance. If tuning CIS w/ lambda, disconnect the O2 sensor first.

The trick to find your engines happy CO is to get the engine at least running and with the airbox cover and filter off, SLIGHTLY lift the air sensor plate via the exposed elbow with a finger, knuckle or whatever. All is needed is very slight pressure to notice any change in RPM. If the engine RPM increases it wants to be richened. This is also true if you were to pull down on the sensor plate. If RPM's increase, then it wants to be leaned out. Make very small adjustments with the 3mm allen as necessary. The trick is to get the engine at a max RPM so when you either push or pull on the sensor plate, the RPM's will drop (from either being too lean or rich)."

[rcaradimos]

Originally posted by kstylianos
From a previous post:

The following needs to be done with the engine warm so the WUR and other CIS components are not compensating for cold enrichment.

"I found that every CIS engine has its particular 'happy place' where it likes to run. No two are exactly the same but CO% usually falls between 2-3.5%.

This can be set by ear and its very acurate for best performance. If tuning CIS w/ lambda, disconnect the O2 sensor first.

The trick to find your engines happy CO is to get the engine at least running and with the airbox cover and filter off, SLIGHTLY lift the air sensor plate via the exposed elbow with a finger, knuckle or whatever. All is needed is very slight pressure to notice any change in RPM. If the engine RPM increases it wants to be richened. This is also true if you were to pull down on the sensor plate. If RPM's increase, then it wants to be leaned out. Make very small adjustments with the 3mm allen as necessary. The trick is to get the engine at a max RPM so when you either push or pull on the sensor plate, the RPM's will drop (from either being too lean or rich)."

Charlie, if I understand you corectly, any movement to the air box flap open or closed should make rpm drop, that would be perfect balance. What would the CO reading be at that point? and is the procedure the same w/ the 3.2l air box? any pics on this?

[kstylianos]

Charlie, if I understand you corectly, any movement to the air box flap open or closed should make rpm drop, that would be perfect balance.

Correct. At this point, this is where a particular engine is happy.

What would the CO reading be at that point?

Happy CO% differs between engines. With O2 sensor disconnected, CO% will be anywhere between 2-4%

and is the procedure the same w/ the 3.2l air box?

No. This is only for CIS injected engines up to 3.0. The factory 3.2's used Motronic where the AFR mappings are totally computer controlled. Steve Wong (911chips.com) can help here if you have a 3.2 with Motronic.

any pics on this?

No pics, unfortunately. The air sensor plate/elbow is exposed in the back in the CIS airbox. If you are totally unfamiliar with how CIS works, the Probst book is very good. For a quick rundown, the air meter plate regualtes the amount of fuel to the injectors. The more air that passes by the plate, the higher the plate rises, the more fuel is delivered. All this is regualted by air and fuel pressures. At idle, the plate is just barely suspended and any adjustments to the plate height here will affect your air fuel ratio in the lower RPM's. Thus, this is why folks like to richen up the mix a little at idle for a little better throttle response.

FYI: This procedure only work if you are going to run open loop (O2 sensor disconnected).

[rcaradimos]

Thanks

[marcar911]

Charlie,

I plan on trying the above method to find the "happy" CO on my 82SC.

Will the richer setting harm the CAT long term? Or, is it safer to run a bypass when utilizing this method?

Marlin

Marlin