83 ROW mixture screw

[AlKidd]

My new to me (Oct '20) 83 ROW has always ran rich. Plugs and tailpipe sniffer confirm that and no oil consumption. Attempted to adjust the air fuel mix with a fellow 911 owner / Mechanic. Nether of us can find the 3mm screw in the hole next to the fuel block. We looked at 2 CIS systems in his shop and both have the screw.
There are many posts on CIS adjustment and some hint at adjusting mixture elsewhere but I wasnt able to search what or how. Am I missing something, or did a PO possibly plug the allen key? We cant even see the extra arm above the main arm of the CIS where the screw would be. All help will be appreciated.

[boyt911sc]

Originally Posted by AlKidd

My new to me (Oct '20) 83 ROW has always ran rich. Plugs and tailpipe sniffer confirm that and no oil consumption. Attempted to adjust the air fuel mix with a fellow 911 owner / Mechanic. Nether of us can find the 3mm screw in the hole next to the fuel block. We looked at 2 CIS systems in his shop and both have the screw.
There are many posts on CIS adjustment and some hint at adjusting mixture elsewhere but I wasnt able to search what or how. Am I missing something, or did a PO possibly plug the allen key? We cant even see the extra arm above the main arm of the CIS where the screw would be. All help will be appreciated.

Alkidd,

To be able to inspect the fuel mixture screw, you need to remove a lot of parts. Even with the AFM (airflow meter) sitting on your bench table, there is sill no direct view of the fuel mixture screw. You can not see it clearly even with a tiny dental mirror maybe a little bit.

You have to remove the following:

• Fuel distributor
• Air flow meter

With the air flow meter on your work bench, continue to remove these:

• Circlip
• Circular metal disc
• Plastic washer
• Ball bearing

Repeat the above removal (circlip, metal disc, plastic washer, ball bearing) plus an extra spring.

We are not done yet, the rod where the sensor arm pivots has to be remove too. It would not slide out because it is held by a screw. The screw is also holding the counter weight. Finally the lever assembly could come off now. See picture below.



That is a lot of work and parts to remove just to inspect or view this set screw. Putting back all these components is another tedious project you got to do. If you like your car to run.

Tony

[icarp]

Just keep stabbing at it , you will find it . Remove the air filter , shine a light ont he sensor arm where the screw should be , this may help you in your confidence to find the screw
Ian
All of us have spent 10 minutes at one time trying to find the 3mm screw

[john walker's workshop]

They tend to get dirt in them which makes it hard to get the 3mm tool to enter. It's in there, just keep poking. You can support the arm through the air filter hole as you stab.

[AlKidd]

Just keep stabbing at it reminds me of something else that was a little awkward the first time however thanks to all for the insight. Thanks to Tonys pic, I can see how it comes apart which wasnt obvious on the spare one but Im trying to avoid removal if I can because the car runs well other than rich. I did try and support the arm from below but couldnt feel it bite at all. Didnt want to put too much pressure as it feels delicate. Will carb cleaner hurt anything? Thinking of sticking the hose in the hole and give it a squirt.

[boyt911sc]

Originally Posted by AlKidd

Just keep stabbing at it reminds me of something else that was a little awkward the first time however thanks to all for the insight. Thanks to Tonys pic, I can see how it comes apart which wasnt obvious on the spare one but Im trying to avoid removal if I can because the car runs well other than rich. I did try and support the arm from below but couldnt feel it bite at all. Didnt want to put too much pressure as it feels delicate. Will carb cleaner hurt anything? Thinking of sticking the hose in the hole and give it a squirt.

Al,

Don’t worry about hurting the fuel mixture screw, it’s very robust and built like a tank. I took some pictures after receiving your PM’s. Below is the picture of the AFM with sensor plate arm partially elevated because it was resting on the table top. Look very closely to the access hole. You can’t see anything.


Next picture, I raised the sensor plate lever and you could see partially the “cup” that has the 3-mm hexagonal key hole.


If you slightly lower the sensor plate lever, the key hole will be directly below the access hole. Put the 3-mm Allen wrench through the access hole and let the wrench locate the cup and eventually lock into the hexagonal key hole. Turn the wrench left or right and you could feel if the wrench has lock-in or not.


Keep us posted.

Tony

[AlKidd]

After a couple PM's to Tony and my favourite suggestion ever, to just keep poking at it till it goes in, plus some liberal spraying of carb cleaner I was able to get a hex key to take hold. For those trying this, avoid hex keys with the ball on the end. They work well in a clean hex hole but wont bite if its gummed up.
Now to do it all over again once I get the car warmed up.
Thanks to all
AL