Help! No clicks on MFI idle adjusting
 

Hello.
I have a problem with 72 S. After adjusting part load to 7.5% CO, I tried to adjust idle speed. I turned the adjusting screw two clicks at each time to the clockwise then measured CO. Totally, I turned six clicks to clockwise and got 5.6% CO at idle speed. After test driving for 20 minutes, I got 7.8% CO at idle speed. WHY? Anyway I had to turn the idle adjusting screw to the counter clockwise to get it leaner. I turned two clicks to the counter clockwise and got 6.4%. I tried to turn it to the counter clockwise to make it leaner, but I could not feel any clicks. I tried to turn it to the clockwise and counter clockwise. NO clicks!! What should I do to get clicks? HELP,please.
Thank you
Takahiro

1) Are you pushing the screw fully in? If I remember correctly, it is spring loaded away from the rack, so you need to push in and then turn until it engages the rack. I assume you knew that since you were already making adjustments, but it never hurts to ask.

Press it and turn. You will feel it click. Write down how many positions you moved it. Are sure the screwdriver is engaging the screw? I had to file mine down a little before it would even go in far enough to touch the screw. The adjustment screw is at least .5" behind the bolt, and probably 1.5" into the pump

Thank you jluetjen,Shuie for your replies.
Yes I pushed and turned toatally 6 clicks to the cw and 2 clicks to the ccw. I got the result through these clicks. When I tried to turn one more click to the ccw, I could not feel any clicks.
Thank you
Takahiro

Takahiro,

Welcome back to the Forum. Seems I remember throttle linkage issues a year or two ago.

Where are you in the CMA procedure? Have you been through the entire sequence and are now finally adjusting the idle mixture?

When you initially had the part load at 7.5%, what was the idle mixture? Would it idle?

Best,
Grady

it's hard to distinctly feel any "clicks" on the idle screw, due to the way you have to access it. i would think your roughly 6% idle mix would be fine. any leaner, they tend to have a less than smooth acceleration off of idle and a poor transition. just what i've noticed over the years.

Grady,Johan, thank you for your replies.
I have done dwell angle and iginition timing,rod correlation and throttle screws. I tuned the part load to 7.5% CO. After that I tried to tune the idle speed.
I got the 5.6% CO at idle once, but after driving it raised to 7.8%. I tried to lean it, but i could not feel the clicks.
Help me please. Thank you
Takahiro

Takahiro,

I guess the basic question is how well does it run with the current settings?

Are you required to pass emissions tests? If not, the criteria is to not dilute the oil with gasoline, not waste gas and have the 2.4 911S engine perform outstandingly as it should.

I’m not trying to avoid your question but I want you to look at the overall picture, not just specifications.

Best,
Grady

Grady and other mfi gurus here.
Thank you for your replies. I have found the black attachment at the end of the idling adjusting tool is free, so I can not feel any clicks.
As Grady said the mfi pump is not a separate component, it should be cosidered as one part of the system. I hope I have done linkage and other things before adjusting CO. The only problem that I have now is the 3rd thorottle plate might be leaking, because if I turn the 3rd adjusting screw about 2 turns like other screws, the air comes much more into the the 3rd, so the 3rd screw is almost closed to get the air volume equally. I get reading of the sychrometer is about 5.5 with the 3rd almost close and others 2 turns open. So the idling speed is 1100rpm. I can not decrese it to 900 rpm. I turned into the 3rd plate stopping screw, no change. I think the 3rd plate shaft might be worn. Is it time to restore the throttle hosing?
Thank you
Takahiro

Takahiro, the best way to check your #3 stack is to remove the throttle body and hold it up to a bright light-- if you can see light coming from around the edges of the throttle plate, that's an indication that it's worn.

John, thank you for your reply.
Yesterday I put the carb cleaner into the #3 stack to see the throttle plate or the shaft is worn or not. #3 idle screw is almost closed. The result was that the motor began to cough. So I think the throttle plate or the shaft is worn and the air comes throgh the plate or the shaft. Do you think this is right?
Thank you
Takahiro