a/c vent closes when on the throttle ...

Their might be a thread out already with this issue but I have this issue wondering if someone can point me in the right direction.
A/C works awesome but when I get on the throttle a little bit the direct air vent blowing towards the passenger and driver shut the blows the air to defrost, then comes back to normal when I let off the throttle. I can here the vent flap shut in the dash and directs the air els where. I was thinking maybe a vacuum line some where any hints before i tare the dash apart???
Thanks guys

Key word: Vacuum

Check all the hoses on the passenger side of the rig. Especially under the battery tray and to the vac reservoir behind the bumper. When all those are tight without cracks, breaks, gaps you should be fine.

I use the smoke test on vac line...makes leaks alot easier to find.

The vac line to follow comes out of the firewall. It's a black line next to a pink or tan line. That runs all your HVAC blend doors. The vac cannister...behind the bumper...holds enough vacuum to supply vacuum when accellerating. When you are off the pedal it switches over to regular (not stored) vacuum.

If you have an aftermarket bumper the ball may be missing. if not, it's there. Several guys/gals?, including me, have relocated the reservoir to the engine bay. Shorter lines, easier to deal with.

thanks ParadiseXJ i will troubleshot it today

Aside from damage to the vacuum reservoir mentioned above, it's also common for battery leakage to eat away the line running to it, so check that line where it runs under the battery.

i had this problem lately, none of the under hood lines were the problem, it was the hose for the blend door under the dash, it is orange and near the passenger kick panel, it was loose.