1990 Lumina Euro Odd Probelm when braking

Hello,

I have the aforementioned 1990 Lumina Euro with the 3.1L EFI engine. Starts and runs well, however, sitting in the driveway, in park, when I apply the brakes the idle drops and almost stalls but not until i release the brake pedal. After the dip it returns to idle. When driving this will frequently stall the car. It does idle a bit high.

I feel it is obviously a vacuum issue but given the symptoms not really sure where to start. Any suggestions? Whould a stuck EGR contribute to this?

Many thanks,

Chris

try disconnecting the vacuum booster. don't drive of course, see what happens, you also could remove the egr and see if it is carboned causing it not to seat fully.

Sounds like the power brake vacuum booster check valve is stuck open. Set the parking brake. Remove the hose from the check valve that sits in the brake booster. Plug the hose. Start car,step on brake,release,step again...any better? Replace the check valve and the rubber grommet it sits in. Should be available at most auto parts stores. Do not drive the car in this condition. HTH