93Euphoria

Friend has a 91 chevy C/K with a carb 350 and he is trying to diagnose why the motor idle really low after revving it. Ill rev it than it drops down to about 300-400rpm for about 2 second before it goes back to 850~ I thought that maybe its his accel pump?! No vacuum leaks!

v8sten

iTrader: (5)

When was the last time the fuel filter was changed?

93Euphoria

He has no idea, he told me he picked up the truck a month ago. Its been doing it since and no one can figure it out.. Nobody knows anything about carbed engines anymore -_-

v8sten

iTrader: (5)

Are you sure its carb'd and not the original TBI?

93Euphoria

Could very well be for the year it is.. Please explain what could be the issue.

cambirdracing

iTrader: (4)

Need to know if it is carbed or TBI before anyone can diagonse it. It makes a difference. A big difference.

93Euphoria

Thats the tricky part. Im not too good with either. He says its stock with the truck. So whatever motor came in the C/K of that year, but maybe both came standard or there wouldnt of been 2 posters ask about if its either carbed or TBI. But my conscious is obviously leading me to a fuel issue.

cambirdracing

iTrader: (4)

91 is most likely TBI. Pull the throttle body and check to make sure that the vacuum port is clean going to the PCV. You will need a new gasket, a few years back, they were cheaper at the dealer than the auto parts store.

v8sten

iTrader: (5)

they didnt come with both. it originally came with TBI. 2 reasons why i asked was you said it was carb'd and its a 22 year old truck and may very well have been changed to a carb.