83 CIS - mixture adjustment screw frozen?

[911gilley]

Just got all electrical probs straightened out on my '83 SC project car. Starts, goes to around 1600 RPM for approx 5-10 minutes, then stalls out when becoming warm. I adjust idle all the way out and it still stalls.

Car started and idled prior to fixing electrical problems/new alternator/new o2 sensor, but not well (starting idle always very high (> 2000 RPM) . Car had bad circuit to alternator light in dash which was causing a non-charging battery and low or no voltage to any components.

I believe that the car's CIS was previously adjusted to compensate for all of the electrical problems by PO, but now that they are fixed, needs to be re-adjusted.

Seems like mixture is bad? I search posts and find method to adjust mixture by "ear" method.

The problem is when I put 3mm hex key tool into hole, the adjustment screw does not seem to want to turn. It seems like tool finds the screw head but screw will not turn. If I push down with a good deal of pressure while trying to turn, it seems like it might be turning, but I certainly do not hear the "clicks" that I should, as the methodology notes.

Can anyone tell me:

1. How much force does it normally take to turn the screw (ie. finger-tip light at 1/2 lb. of torque, or harder at 2 lbs. and leverage at end of tool)?

2. At what intervals should the "clicks" be heard (ie. 1/8, 1/4, 1/2 turn)?

3. Is the screw frozen or missing possibly? Can one lubricate it in some manner?

4. Has anyone had this problem before?

Any insight greatly appreciated,
-Ed

[mb911]

Most adjuster that I have seen do not click! The screw should turn easy as all it does is change the air meter hieght and nothing else. I am not sure but I think if you take the air filter off you can see the allen wrench through the opening ( I have never looked before)

[ruf-porsche]

Don't think that its the mixture screw that is causing your problem. WUR? Maybe the famous vacuum leak. What happens when you remove the oil cap when the engine is running?

[mb911]

Do you think that the engine will always drop when removing the oil fill cap??

[911gilley]

Ben, I'll check that out.
Ruf-porsche, my WUR does not have the vacuum (I believe that was CIS pre-'81); the K-Jetronic Lamda has the o2 sensor, which I believe replaces the vacuum in this "newer" system ('81-83 CIS). It only has the hard lines -- 1 in from the fuel dist (control pressure), and 1 out back to the fuel return plus electrical hookup.
I am guessing that because the proper electrical current restored + new o2 sensor installed, the mixture is now off (not tested, but maybe the WUR has correct pressures now as well as a proper o2 reading due to the above "fixes" and so the mixture is now throwing off the idle?)
Just hypothesizing......

[911gilley]

Ruf,
I will try the oil-cap thing. What does this establish?

[mb911]

Thats what I was wondering as if it won't idle it means its to rich not enough air..

[911gilley]

Yeah. I'm going to try what you suggested and see if I can get a visual on the screw from the airbox side to see if it's frozen/missing. If I get it to move, I'll try to lean it out (by turning counerclockwise) a little to see if i can get it to idle. I guess I should keep the idle screw cranked all the way out to maximize idle until I can get it to idle, then work it back in while adjusting the mixture, and continue doing this back and forth?

[ruf-porsche]

Opening the oil cqp will cause a massive vacuum leak, so if it doesn't idle with the cap on but idle with the cap off we can conclude that the air mixture could be too rich.

However if nothing happens, we can conclude that perhaps you have another vacuum leak somewhere else.

If the idle drops down like it is suppose to we can conclude that the mixture is correct.

[ruf-porsche]

Originally posted by 911gilley
Ben, I'll check that out.
Ruf-porsche, my WUR does not have the vacuum (I believe that was CIS pre-'81); the K-Jetronic Lamda has the o2 sensor, which I believe replaces the vacuum in this "newer" system ('81-83 CIS). ......

Vacuum could be leaking from other vacuum hose, not just from the WUR (if you WUR has vacuum lines).

[911gilley]

Ruf,
You're right. I did check vacuum hoses on car and all seem good. Will try oil cap thing and re-check vacuum hoses though.

[mb911]

remember that the car has to be completly warm when checking otherwise the aar will be making a vacum leak enough said

[Sunroof]

Talk about frozen adjustment screws?
Here's my story so maybe this will help..........................

I could not turn my screw as well and it turned out the previous owner put locktite on it! Simply, remove your filter housing and hold the bottom of the sensor plate with one hand, while you adjust with the other. I had to pick out the licktite with a dentla pic, but shot some BP blaster in their to help loosen it up.

This might work for you.

Bob
73.5T

[Paulporsche]

Sometimes the allen slot in the head gets gummed up w/ dirt, sound pad crumbs, etc. If you stick the allen wrench into where the slot should be and then drop some PB or other solvent down it into the slot, that should loosen things up. You could also use a wire to pick out any debris. If you look in after removing the air filter, then you will be able to tell if you are correctly located. It is easy to think that you are in the slot, when the wrench is actually sitting next to the screw and turning nothing.

The adjustments on both my 77 and 80 engines do not click.

Do you have the plug that fills the access hole, so you do not get gunk down in there?

[911gilley]

FIXED!
Tremendous thanks to all that replied. 2 major problems I found:
Here's what I did:

1.)BAD O2 WIRING HARNESS CONNECTOR
Connector on harness side of oxygen sensor (in engine compartment, the little white barrel with a brass pin sticking out of it located below fuel accumulator) was cracked off and hence sensor wire not connected. Plus, I think the harness wire shorted out back to ECU (Motronic brain unit under passenger seat). This wire is a green 16Ga wire with a "shield" running back to pins 2 and 4 on the ECU. I think the severed connector caused it to short itself out to the shield and cause the ECU to think that the car was running rich or lean or something. I cut the old connector off and luckily had an entire spare wiring harness for my car where I harvested another connector. I reattached the new connector, being careful to isolate the splice for "inner" wire and "outer" braiding.

2.)UNFREEZE MIXTURE SCREW AND ADJUST MIXTURE AND IDLE
Took off air filter and cover so I could see adusting screw and mechanism. Sprayed some Lubejob (like WD40 but better) into area and let sit. Screw now turning much better and I could visually see it turning (with mirror on airbox side).

Took out idle adjusting screw and cleaned off (for those following this thread, this is a different screw on side of throttle body, not the mixutre adjusting screw). Replaced and turned all the way in, then back out approx 2 turns.

Disconnected o2 sensor.

Started engine and after 4-5 minutes it stalled out (warmed up a little bit).

Restarted engine, it ran for 4 seconds, then stalled.

Turned "in" (clockwise) the mixture adjusting screw approx 1 1/2 full turns. Started engine, it ran for about 1 minute and stalled.
Turned "in" mixture screw another 1/2 turn. Turned out idle adjusting screw 1 more full turn. Started engine, it ran but was rough but RPM decent at around 1100. I let it run for 10 minutes like this to get a good warmup.

Turned "in" another 1/4 turn and began to run well.

Turned "in" antoher 1/8 turn and began to run perfectly smooth.

Adjusted idle to 850 RPM.

Took her for a test drive approx 40 miles.......RAN PERFECTLY SMOOTH, acceleration crisp, returned to perfect idle at any stops, no hesitation, no backfiring. When I remove oil cap, engine RPM drops and goes toward a stall like it should.


In conclusion, I think that the O2 sensor wire had some bearing on the poor performance of the CIS, but that the mixture adjustment was off as well. I know that the spec for adjusting the mixture instructs one to "disconnect o2 sensor" before making adjustments, so that even with it disconnected the car should be able to idle. Buy my car wouldn't. Even after I fixed the broken wire/connector. Unless the "shorted" wire on the connector was causing the ECU to try to send a constant correction to "lean" out the mixture?

[911gilley]

The car seems to be running great now. I also reconnected the o2 sensor after completing all adjustments. Do I have the mixture correct? Should I take it somewhere to put a gas analyzer on it to check? Could it seem to run perfectly and still not be adjusted properly?

[Westy]

Originally posted by 911gilley
FIXED!
Tremendous thanks to all that replied. 2 major problems I found:
Here's what I did:


Took out idle adjusting screw and cleaned off (for those following this thread, this is a different screw on side of throttle body, not the mixutre adjusting screw). Replaced and turned all the way in, then back out approx 2 turns.

Disconnected o2 sensor.

Started engine and after 4-5 minutes it stalled out (warmed up a little bit).

Restarted engine, it ran for 4 seconds, then stalled.

Turned "in" (clockwise) the mixture adjusting screw approx 1 1/2 full turns. Started engine, it ran for about 1 minute and stalled.
Turned "in" mixture screw another 1/2 turn. Turned out idle adjusting screw 1 more full turn. Started engine, it ran but was rough but RPM decent at around 1100. I let it run for 10 minutes like this to get a good warmup.

Turned "in" another 1/4 turn and began to run well.

Turned "in" antoher 1/8 turn and began to run perfectly smooth.

Adjusted idle to 850 RPM.

Took her for a test drive approx 40 miles.......RAN PERFECTLY SMOOTH, acceleration crisp, returned to perfect idle at any stops, no hesitation, no backfiring. When I remove oil cap, engine RPM drops and goes toward a stall like it should.

Congratulations Ed

Just one question. Did you just figure out this adjustment sequence, or is this a procedure someone explained to you? Just curious, 'cause I was having some of the same issues.

Thax,,,Brian

[Paulporsche]

Ed,
You have several options:
For a more secure peace of mind you can have a shop measure and set your CO and tell you what the setting is. This is important if you have to meet emissions requirements. If not, JW recommends 3.5%. Or you can try the push/pull method on the air sensor to see if you are set correctly. Or you can richen the mix until the idle speed fluctuates and/or the engine wants to stall when the car comes to a stop. Or, if it seems to be running just fine now, leave it and drive. You may have to adjust it later as the summer temps rise, and again in the fall. Either way, that should only be a very small increment, say 1/16 or 1/8 turn.

[911gilley]

Westy, I just figured out that adjustment sequence. I think that in the beginning when the screw was tight, I might have been turning it back and forth without knowing that I was, thus throwing it further out of wack.
I think I just lucked out by choosing to turn it in the 1 1/2, then another 1/2....I just flipped a coin to make that decision and it seemed to get me in the right range (by allowing car to idle) so that I could make the final "finite" adjustments.

Paul, I think I will just leave it as is for now and drive it. The push-pull creates a stalling effect either way like it should. I may pick up a gas meter if I spot a cheap one.

[SCWDP911]

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