vac leak intake

i have a 96 bravada just bought 89000miles super clean but when it is cold outside it idels high. does it hot some times but mostly cold i can hear a sound like a vac leak comeing from around the intake manfold.i replaced all the vac lines i could find. they were real bad but still held a vac could it be the intake gasket or is ther a line i am mising.

Check all connections around the intake.

Check the pcv valve hose and make sure the pcv valve is seated properly.

ye my pvc vaulv fits very loose into the vaulv cover but when running is tight becaues of the pull of the vac

it should be tight at all times.

that is your vac leak.

ye my pvc vaulv fits very loose into the vaulv cover but when running is tight becaues of the pull of the vac

the rubber seal (in the valve cover) that the pcv sits in, can be replaced if its loose, but its common that its not as snug in its seal when the vehicle is off. it makes plenty of hissing sound unplugged, so it may be the noise if theres a leak. Id replace it if its loose. Theres a few gaskets in that area that can be leaking as well you might want to check in addition to the the PCV and Vac Lines. Theres a gasket around the fuel spider that seals it into the upper intake cover....a gasket around the cover itself, and a third that seals the throttle body. All three come in a kit together for approx $30 from GM Dealer. Just worth checking all three.

FYI - you may want to get as close to the leak sound as you can and spray a slight ammount of starting fluid in the area (on the pcv, etc) paying attention to any change in rpm after you spray each area. If the rpms rise for a second and fall, you probably just hit the leak source and it sucked the starting fluid into the intake.

You can use a propane torch to check for leaks. Turn gas on and run around possible leaks. Listen for rpm change.

Carb cleaner would also work and be a little safer.

thanks blazer lt and joshbarber im also going to do blazerlts pvc catch can it is a very good idea and cheap i will post some pics of the mod later

You can use a propane torch to check for leaks. Turn gas on and run around possible leaks. Listen for rpm change.


yeah, uhm...I wouldnt reccommend using a propane torch for this. something about a steady flow of propane gas near possible electrical connections (shorts or not), and a constant spark from the plugs......