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
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.