Air / Fuel adjustment

[95pontiac]

How do you set the air/fuel adjustments on a Motorcraft 2150 2bbl carb on a 360 V8 ('88 Grand Wagoneer).

The idle speed and choke are set correctly, but it runs a little rich. I just plugged a vacuum leak that I had.

In addition, do you close both air/fuel screws at the base of the carb(clockwise) and open them the same number of turns, or do you set them independently?

Thanks!

[Serious Johnson]

Poncho:

Idle A/F mix is best set using a vacuum guage, adjusting each screw for the highest reading. Lacking a guage, it can be fairly approximated by iteratively turning each screw SLOWLY and settling on the setting that results in the highest idle speed. You'll need to then reset the idle and try it again, and so on until you get tired. Making the final turn clockwise seems to help prevent future changes from vibration.

I assume that you understand that this only affects idle, and that open-throttle mixture change requires swapping jets.

Note also that rich running can result from such common faults as a blown power valve or clogged cat.

:-

[ February 10, 2003, 01:44 PM: Message edited by: Serious Johnson ]

[Don S]

..
95pontiac ...
... Just thought you might need or like some tech links

http://www.ifsja.org/tech/fuel/2150.shtml FSJ MC-2150 CARBURETOR

http://home.earthlink.net/~bubbaf250/2150carb/carb01.html MC-2150 CARBURETOR

Good Luck ;) and CUL.. Don S..

[crispyboy]

btw - how do you use a vacuum guage to check the idle mixture-
where do you attach the vacuum guage?

[Don S]

Originally posted by 13lftmfsj:
btw - how do you use a vacuum guage to check the idle mixture-
where do you attach the vacuum guage?..
13lftmfsj:...
...... There is no indication of which engine you have but hook the vacuum gauge up to the intake manifold. At this point you can follow the advice given above by Serious Johnson.

Below is another way to do it from the IFSJA tech files

http://www.ifsja.org/tech/fuel/2150.shtml
Good Luck ;) and CUL ;) … ds..

Copied from;http://www.ifsja.org/tech/fuel/2150.shtml

Michael Baxter
Final Set-up:

* Idle speed & mixture adjustment: It is crucial there are no engine vacuum leaks in order to adjust the idle mixture and idle speed and obtain a smooth idle. Vacuum leaks can be diagnosed using spray carb. cleaner. Ensure the vapor can't enter the carb. normally and spray around any engine vac. connections. You may have to plug some vacuum lines which run through the fire wall in your process of elimination (as you shouldn't spray carb. cleaner inside the FSJ). Don't forget any vacuum connections around the transfer case and front axle as necessary.

- Warm the engine to normal operating temp.
- On the anti-diesel solenoid bracket, the normal idle adjustment screw faces rearward. Most use a 5/16" wrench to adjust.
- Set the idle speed to a reasonably low level.
- Chock the wheels and set the emergency brake.
- Put the transmission into Drive if automatic transmission.
- Set the normal idle speed to the underhood sticker specs, the Service Manual specs, Carb. kit specs or your preference.
- Disconnect the single wire for the anti-diesel solenoid. This shuts-off electrical flow and the solenoid retracts.
- Using the idle speed adjusting screw located on the carb. body adjacent to the driver's side throttle shaft/linkage, set the idle speed to 500 RPM or less.
- Plug the anti-diesel solenoid wire connector back together, put the transmission in Park temporarily if an automatic and then blip the throttle valves once as the solenoid is not capable of opening the throttle valves by itself.
- Now adjust the idle mixture screws in very small increments for a smooth idle. A little adjustment goes a long way when it comes to the idle mix screws. Try turning them in (leaner) 1st. They shouldn't need any more than 1-1/2 turns out nor less than 3/4 turns out. If you loose track, you can turn each screw individually until it seats (gently) and then back out the desired number of turns without the engine dying (it'll run rough though). I find 2150s usually around 7/8 of a turn for 360s. On the 2150-2, it is easiest to adjust the driver's side screw if you 1st disconnect the EGR vac. line. Since this is a port vac. source, it doesn't need to be plugged. Remember to reconnect it when done.
- readjust the idle speed as necessary after setting the mixture screws.
- Put the transmission in Park and shut-off the engine when complete.

This is another adjustment which might need to be made seasonably. In the Summer when the hot air is less dense and the accessory load (A/C) higher, you may want to adjust the idle up a little. Vice versa for Winter.

* Fast idle speed adjustment:

- Open the throttle valves at the carb. and hold them open.
- Push the choke valves fully closed and hold them there.
- Release the throttle valves and then choke valves can be released. This sets the fast idle cam.
- Start the engine but, don't touch the accl. peddle or throttle shaft at the carb.
- Adjust the fast idle screw located on the lower choke linkage on the passenger side of the carb. to the spec.'d or desired speed.
- Blip the throttle and the fast idle mechanism will release.

* Miller Time! Substitute your favorite libation for "Miller" as required. :)

Corrections and comments gladly accepted.