Does anyone know of a web site or have information available for the
proper sequence of adjusing all the different idle adjusting screws
on the 1986-89 Accord carburator?
I cleaned the carburator (which was full of dissolved filter
material) and repaired all the broken diaphragms attached to the
carburator, but am at a loss how to correctly adjust all the idle
adjustments that this carburator has.
To set the fuel mixture manually, you'll need to perform a propane boost
test. The tool distributors make an expensive special tool for this but you
don't need it. Just get a regular propane torch and remove the flame tip.
Now, attach a section of plastic tubing about 5 feet long. Attach a
tachometer, and with the car running, remove the top of the air cleaner and
slowly feed propane into the primary barrel of the carburetor, i.e., open
the torch's valve slowly and continue until the idle peaks out (but stop if
it's more than 500 rpm you may need to adjust the idle mixture screw before
proceeding). You should get an idle boost of about 100 rpm when the fuel
mixture is set correctly. Adjust the idle mixture screw so that you get the
correct amount of boost. Afterwards, set the idle speed screw to the specs
on the underhood sticker, usually about 800-850 rpm for a car with a manual
transmission, and recheck the timing.
I've never seen a Honda carburetor without a mixture screw. However, on
many models, Honda installed a metal guard type plug over the mixture
screw. The mixture screw can still be accessed but the plug has to be
removed first and this usually requires removing the carburetor since the
screw is at the bottom back end of the carburetor next to the firewall.
That could be why I've never found it... but then I've never seen any
mention of it in any shop manuals either. The consensus on another
board is that mixture is controlled by the "ECU" (such as it is) and
isn't user-adjustable on the third-gen Accords.
The procedure is described in the factory service manual from Helm. It's on
page 11-22 in my copy. You can get one from http://www.helminc.com . It is
not surprising that other manuals, such as Haynes or Chilton, do not include
the necessary level of detail that is found in the official factory service
manual from Helm.
While it is true that Honda used feedback carburetors for fuel control under
different driving conditions, the base fuel mixture is set via the screw at
the back of the carburetor. The factory service manual actually specs a
propane boost of 60 +/- 20 rpm. However, a boost in the range of 75 to 100
should be fine as per my prior post. When servicing a Honda carburetor,
I've found that it's best to follow the directions which are included in
Honda's factory top clean kit. This kit was put together many years ago by
a dealer Honda tech who developed a relatively fast and easy way to service
Honda carburetors without removing the carburetor from the manifold. The
kit even includes a replacement o-ring and washer for the idle mixture
screw. The only problem is that you need to remove the carburetor in order
to access the screw on cars with the mixture screw cap. The top clean kit
also does not include floats which must be purchased separately if needed.
I forgot to mention that the first step is usually to set the float height.
There should be a window on the side of the carburetor with a black dot at
the center. The float height adjustment is correct when the fuel level is
at the center of the black dot in the window.
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