Adjusting CIS Fuel mixture

[x98boardwell]

Question,

I failed my smog test this past week. They said that I was running too rich.

1) How do I adjust my CIS mixture screw?
2) Which way changes to richer or leaner?
3) What increments do I use when adjusting.. 1/3 turn, 1/8th, etc.?
4) What is the "by ear" method? Can someone explain this?

I have searched the forum for this using several different descriptions and only have come up with the air/fuel issues, not how to actually lean out the motor.

Maybe a diagram or drawing of the system would help.

Thanks in advance for all of your help. If there is a thread that I have not been able to find, please provide a link and I will be happy to go there.

Merry Christmas,

Bryan

[fred cook]

You will need a long 3mm (I think) allen wrench to make the adjustment. There is a small hole just to the left of the fuel distributor. The allen wrench goes in the hole and into an allen head screw. To lean the mixture, turn the allen wrench in a counterclockwise direction. A very small movement (1/8th of a turn)will make a large change in the mixture. It is best to use an exhaust analyzer when doing the adjustment. You can buy a CO (single gas analyzer) for a reasonable amount of money, even for a hobbyist.

Good luck!

Merry Christmas and a Happy New Year to you and yours!

[Paulporsche]

Bryan,

A little more in depth searching may be required. Your questions, and their solutions, are very common on this BB.

Try searching Souk. He has a field test AKA the push/pull method for setting CO. There are also typical symptoms, eg a too rich mixture usually yields a hunting idle.

Check out Jim Williams. He has a Rennlist site on CIS which is very good.

Get to know the CIS components, especially the WUR, the AAR and the decel valve, all of which are common problem areas. The Bentley manual has a lot of info on CIS.

Your adjustment tool needs to be about 5" long an 3mm as Fred said. The adjustment screw is way down in the FD. Depending on the year of your engine, it may be easily accessible via a plug that can be simply pulled out, or may have to be drilled out.

I usually use only about 1/16 turn increments. Keep in mind that 1 complete revolution is equal to somewhere between 8 an 12% which is a huge amount.

Always complete an adjustment by turning clockwise, ie lean to rich. Good luck.

Some of us have our own ways of tuning by ear. The sound of the engine, how it revs and idles, tells you a lot about how it is running, but it helps to have experience w/ this.

In general, these engines need richening as they age. Also, often times people will richen the mix to make up for other problems. Ignition items, vacuum leaks, and general engine conditions should always be resolved before looking into the CIS.

A CIS fuel pressure gauge, avail from JC Whitney for $60, is helpful in diagnosing problems.

You might want to have someone w/ a gas analyzer set the mix so you have a baseline. Also, since you are in CA you have to meet regs if your car is newer than a 76.

You should state the year and model of your car, do more searching, and let us know how you make out. Good luck!

[911nut]

I just want to add that if you can't turn the screw once you have the allen wrench in it, the allen slot may be filled up with dirt. In that event you will have to clean it out.

[x98boardwell]

My apologies,

I have a 87 930. It is completely stock and passed 6 months ago with the previous owner.

Question, Was it Counter Clockwise to lean out or Clockwise? It looks like there are both in the posts.

I wonder if he had to lean it out to pass or not?

I will do some more searching to find those threads. I appreciate all of your input thus far... keep em coming. I will update when finished.

Thanks
Bryan

PS. I got the car from Santa. I have owned for less than a week. Great gift to myself. Here she is.

[shbop]

Counter clockwise-lean. Clockwise-rich. I think Paul was explaining that he always ends the process by going from a lean to rich condition. ie- adjust on the lean side, and bring it back to where it should be. Hope this helps.
Merry Christmas

[Paulporsche]

Your car looks great!

Some people have trouble fitting the allen key in the adjustment screw. You have to develop a feel for it. Also, as Paul B said , you may have to clean out the slot. I like to fit a skinny point, like from an unbent coat hanger, down in there to clean out debris. You can also dribble A LITTLE WD40 down the wire into the slot to clear away gummed up stuff.

Jon is right. CCW lean CW rich.

After you do an adjustment, remove the allen wrench and rev the engine. Don't rev w/ the wrench in place.

If you check the exploded parts views on his site, I think you will find a drawing of the fuel distributor.

I would consult the PO about his techniques for passing smog tests. You will find many techniques used by others by searching here.

[ninesixfour]

Just take it to a shop with an exhaust gas analyzer and let them do it. You'll never know if it's right without this equipment. I've had it done twice in the last 2 months (first time when I changed the exhaust, second time after changing plugs, wires, etc...) and I watched both times. It takes about 10 minutes and the mechanic doesn't even charge me for it.

[Jay Laifman]

Two comments. First, the little allen key adjuster is intentionally firm. A standard 3mm long reach wrench works just fine. But, the job specific "tool" is much nicer. It is just an allen key but the top is a large looped piece rather than just a little 1" bent end. It gives MUCH better leverage to make the turning simple.

Second, be careful with turning it lean to make the car leaner. A car that is too lean already can show rich on the tester, and you will only be making it worse. But, if the car is that lean, it probably would have less than perfect driving characteristics.

I went to my local smog shop. For $10 they let me hang out and adjust till the cows come home, as they say. That said, my car is still not running well and there is nothing left to change!

[x98boardwell]

In the picture below, what is the white arrow pointing to? What does this do? This can be pushed down with pressure... Not sure why.

Is the fuel adjustment screw inside this? Or more towards the center of the CIS?

Thanks

[turbobrat930]

Bryan, That is the mixture adjustment screw that you are looking for...... in a 930, you may not even need the allen wrench....just push down and turn... making very little adjustments.... IIRC, you can have the motor running when you do this... but you can rev it up until you release the spring, and have it return to the state that it is in the picture.... then rev up the motor to stabilize the mixture and pressures....and then that is the spot where you can take another reading on the test equipment.....

[JFairman]

Originally Posted by x98boardwell

In the picture below, what is the white arrow pointing to? What does this do? This can be pushed down with pressure... Not sure why.

Is the fuel adjustment screw inside this? Or more towards the center of the CIS?

Thanks

That little aluminum thing the arrow is pointed at has an aluminum plug in it from the factory to keep people who don't know what they're doing from messing with it and screwing it up...
Looks like the plug is already removed so you can insert a short 3mm wrench in there, push down carefully and turn lightly until you feel it engage.
Then turn
right_for_rich
and turn
left_for_lean
Do not rev the motor while the wrench is in there or you may break or bend something, and do your final small turn to the right.
Only turn it a tiny bit at a time.

[x98boardwell]

Well,

Smog is a success!!!! The PO had adjusted the mixture to an extremely rich setting to compensate for a poor running motor.

Problem you ask... It was the two orange colored seals that are inside the intake between the turbo and the intercooler. One was cut and the other was almost non-existent. $4.00 for seals. Also, a slow adjusting O2 sensor.

Then, it only failed smog becuase of NOX, so swapped out a catalytic converter (so generesly donated by another pelicany) and it was as clean as my 06 (HEMI) Jeep Grand Cherokee.

I would love to know who was working on this before. Now, she purs like a kitten and shows better fuel economy as well.

Hope this can help someone out there. Thanks to all who replied and offered suggestions.

Bryan