anyone know what could cause this????

whats up guys. i have a 89 mazda b2200 carbed, and the problom im haveing is that once it warms up and the choke kicks off and im idling at a stop light the idle will change from like 750 and in exactly 5 seconds it will rev up to 1100 and then in 5 seconds it goes back to 750 and so on. what can cause this???? the engine is totally stock and runs fine other then that. thanxs for the help ahead of time!

You need to rebuild your carb for like $10 bucks

ya my 87 carb doesnt do that but its fucked as well, garbage.

i had a couple vehicles that did that in the past but they were not carbed. 2 times out of the 4 it was the a/c clutch engaging on its own. then the engine would idle up as if if were trying to compensate.

If it is anything like a Nissan factory carb you have an air to fuel ratio selinoid at the base of the carb and that is what it sounds like is going bad. There is a spot you can drill out carefully and there is an adjustment screw. Doesn't always work though and may not be something you would want to mess with yourself. If the carb is going bad you can get a Webber for less or about the same as a factory replacement($300-$350)and it is alot better and cleans up all the vacume lines and relays and shit. Hope this helps a little.