Sensor Plate & A/F Mixture Baselines?

[jh225]

About ready to pull my hair out.

'77 3.0 (Turbo, but that should not be a factor).

First off, at idle, where should the sensor plate be? Should it be all the way up at the top of the housing, down a bit into the housing, down halfway, etc?

Secondly, what should the baseline for the A/F 3mm screw be? (example: like on a Quadrajet, all the way in, and then out 2 1/2 turns will get you in the ballpark)

Here is the problem.....................

Car is new to me. Came as no start/no run. Got the no start fixed (wiring) and then went onto the running issue. It will idle, but as soon as it comes off idle, it will hesitate and/or stutter, then want to die/does die.

New plugs, cap, rotor, drained tank, etc.

Reason I ask about sensor plate position is at idle, the plate is all the way at the top of the housing. Any attempt to push down on the plate or push the throttle linkage results in the stutter/stall.

Doesn't seem like it would be a WUR issue from what I have read, but I know zippo about CIS.

And now after playing with the timing & A/F screw the car won't even start (could be flooded, but probably not) which is why I need to know baselines.

And yes, with the key in the on position, pushing on the sensor plate will start the 2 pumps.

Thoughts?

[Paulporsche]

If you see the unit in section, you will see it is a cone shape. The walls slant in to a point where there is a waistline, where the wall is vertical, and then starts to flare back outward. The highest point ot the sensor plate face should be even with the the point where the cone changes its slope. This is @ rest. I'll try to find you a pic.

[Paulporsche]

This is for a NA engine. I really don't know if a turbo is different or not.

[jh225]

Originally Posted by Paulporsche

This is for a NA engine. I really don't know if a turbo is different or not.

Yes, same for the turbo as I found the online manual.

That is where mine sits. Basically, it just comes high enough to make a seal. BUT, I still need to know about the A/F screw as I can't get the car started. Turning the screw tightens or loosens pressure upon the plate, but if I don't have a baseline, I am still screwed up.

[longhornchris04]

If its the same as a NA car, then clockwise is rich, CCW is lean. At idle, it should be sitting just in the throat, as that is the minimum amount of air flowing through. I don't think there's a "default" location as it will depend on the variability of your control pressure, altitude, and other factors.

The adjustment screw simply alters the pivot slightly. The venturi shape (funnel) is calibrated such that you should get the correct AFRs provided that:
1- the idle point is set correctly
2- your control pressure and control pressure regulator (WUR) are working properly

Of course, right now you are fiddling with one of the adjustments w/o having any idea if the rest of your system is set right. It won't matter what you do with that screw if your control or system pressure are out of spec.

The first thing to do is acquire a set of CIS pressure gauges. With these, check your system and cold control pressure to make sure they are in spec. You can't check the warm CP w/o getting the car running, so assuming you can get those corrected, the next step is to adjust that set screw until she fires up. Personally, I would crank it way rich and lean it off until I go the motor to catch... taking breaks to let the starter cool. You should probably have the battery on charge inbetween attempts.

Once running, let the engine get up to operating temp... it may take a while at idle. If it hunts, then you are rich... you will probably have to lean it out as it heats up. Additionally, you may have to adjust the idle bypass to get your idle speed correct. Adjusting the AFR will affect idle speed.

After you get to this point, I would take it to someone with an exhaust analyzer. I know that with NA cars that aren't emissions tested you can get away with a "by feel" adjustment... I don't think I would risk it with a turbo.

Based on your description, you were running rich. I have no idea what you adjusted it too, but here are the signs (in an NA car) that you are rich:

1- hunting for idle / osciallating at idle (this can also be vac leak)
2- white smoke (this can also be oil)
3- fast RPM fall when off throttle - in mine it was like I didn't have a flywheel
4- trouble "capturing" idle - my idle is right at 1k rpm, but the revs would fall to ~500 before comming back up... or she would stall. This happened once in a turn when I was trying to downshift. A little thottle as I eased out the clutch and she spun back up. I quickly pulled over and made an adjustment.

Very slow adjustments toward lean allowed me to get rid of the hunting. I had to drive the car to get rid of the fast RPM drop and get a good idle return. Find a nice empty road, run the engine up then off the gas and pop the clutch... watch the engine fall to idle. Make note of the performance and adjust when I got to the end of the road. I still haven't had my exhaust checked, but I know I'm not running lean so I'm safe. I also had the benifit of having my pressures checked by the mechanic. The reason I had to adjust my settings is that I'm in Cali and the car was tuned for emissions. Idle ended up too high and was abnoxious.

[Paulporsche]

There is no "starting point" on these things. As others have said, you have to make sure the warm cp is right first, then the cold cp, and then the mixture. You can try Souk's "Push Pull " method for field setting the mixture, but, as chris said, I think I'd make sure I set it w/ an analyzer @ all throttle settings w/ a turbo.

[jh225]

This is the correct one for my '77, right?

From our host.... TOL-TA33865 Tests C.I.S. Non-Electronic with metric threads, C.I.S./Lamboda Electronic with metric threads and C.I.S. E-Electronic with metric threads.

[longhornchris04]

Oh, and you may want to post this question in the 930 forum. The turbo-CIS experts live there.