mobird

Hey guys,

I'm pretty sure my quadrajet has a big vacuum leak. It's not running great (surging idle, inconsistent idle, not great throttle response). The reason I'm thinking it has a vacuum leak is that if I cover the mouth of the carb the idle revs up (should die if it's working properly right?).

I already tried spraying carb cleaner all around the base of the carb with no effect. I checked all my vacuum caps and they all seem to be in place and crack free. Where else should I be looking for a leak?

Thanks.

'75

If it has an auto trans, check the vacuum hose to the modulator. Also check the brake booster for a vacuum leak.

mobird

Manual trans. What's the best way to test the brake booster?

croaker

Cap the ports one at a time

mobird

Will do. My cars pretty loud (side pipes) so I gotta wait till it's a little later in the day before firing it up and testing.

lars

Simply disconnect every vacuum line to the carb (including power brake line and PCV) and cap every one of those ports on the carb. If it still has the same symptoms, you have a lean condition, not a vacuum leak.

Lars