87 honda accord idles rough

i have an 87 accord carb. engine. when i first start
it up it runs fine but after it runs a little while it starts to idle
rough. it will rev up to 1200 rom's then drop down till it almost cuts
off then it will rev up to 1200 rpm's again. it will do that a few
minutes then cut off. it will start back up fine and then it might do
it again or it might idle ok thanks

 

Check for vacuum leaks. The most common is the carburetor base gasket. You
can check this by spraying carburetor cleaner around the base of the
carburetor. If there's a boost in the rpm then a leak is most likely
indicated (note that you can also do a propane idle boost test - search the
newsgroup for posts where I've described that technique). However, a vacuum
leak could also be due to a broken piece of vacuum tubing this typically
occurs at bends in the tubing. Sometimes you need a small mirror and a
flashlight to check the vacuum lines.

Also check the distributor advances. The vacuum advance should hold vacuum
and the mechanical advance should allow the distributor rotor to turn 10-15°
and then spring back. If it doesn't move freely, then the distributor may
need to be overhauled due to a stuck mechanical advance mechanism.

Eric