Rpm Doesn't Drop As Fast As It Should Be.

[blueapple]

I have a 88 Corolla SR5 Carb engine.

Now the problem is, when I let go the throttle and push the clutch in, rpm doesn't drop as fast. It takes 3-4 or even more seconds to drop to idle speed, and sometime doesn't even reach idle speed.

I think it's the choke plate. The car used to have a problem starting cold. But that was solved by washing the butterfly with carb cleaner. ( so it doesn't stick anymore) But the dropping slowing in RPM problem is still there. Very annoying when shifting fast.

One more thing that I have notices is: the choke plate is spring loaded when it's cold, and the plate just play freely when it reaches operating temperature. is it normal?

what could be wrong?

[Unity Jon]

at normal temp the choke should be wide open for unrestricted air flow, If your butterfly was sticking perhaps your jets are blocked, especially if some of the carbon build up from the butterfly has dropped into one of them ?

count how many half turns are required to remove the jet, when its out clean it with spirit, fuel, carb cleaner...whatever you have handy, blow through it gently in BOTH directions then screw it back in th exact same number of turns required to remove it.

Do this for the fuel and air jets.

hope it helps.

[blueapple]

Thanks! but I was wondering, if the jet is blocked, shouldn't it be dropping faster? since there won't be enough fuel? This thing occasionally drops pretty fast, but regularly dropping very slow.

What is controlling the dropping? I know there is a piston or something that slows down the dropping, so the shifting can be easier... which one is it? is it controlled by vaccum?.. or electronically?