1995 chevy lumina dies when stopping and reversing?

My brother's 1995 chevy lumina 3.1 engine has been dying while braking for a stop and while reversing. Has replaced fuel filter, map sensor, throttle sensor, o2 sensors and still no change. He says he doesn't believe a tune-up is the cause either.
Any ideas?

Put it in neutral or park running. Step on the brakes. If you see rpms fluctuating, suspect brake booster check valve. Relatively cheap.

Does it start right back up, are there any other performance issues?

Put it in neutral or park running. Step on the brakes. If you see rpms fluctuating, suspect brake booster check valve. Relatively cheap.

he tried that method but there was no change in rpm.....the car starts up fine even after dying but he said that sometimes it acts as if it doesn't want to start....i remember a few weeks back when he put the car in reverse gear it would die on him unless he would give it some gas (sometimes it still would die)

yesterday he tried disconnecting the brake booster and using the brakes to see if it would stall but the brakes just became hard

If you have an egr valve disconnect the plug see what happens, also clean the throttle body and remove the iac and clean that also.

If you have an egr valve disconnect the plug see what happens, also clean the throttle body and remove the iac and clean that also.
I'd have said "test the IAC"; with cleaning recommended if the thing works at all.

I would suspect IAC aswell. Maybe Battery connections? Ive also heard on older cars that 3.1l that is, that the computer wiring will begin to come lose at the ecm. Just a couple of ideas thrown out there. IAC couldnt be more than what 30 bux or less? Pull one from a scrap yard haha, and clean it.

Plus the thing HAS to have a check engine light on. What are the codes? Could be crank shaft POS sensor, if that doesnt work it will die. There might be two of them aswell. Another idea.

I agree with Max......try cleaning the throttle plate edges, and the mating bore in the throttle body, remove the IAC and clean the pintle and the surface of the mating passageway.....check the connection in the harness for the IAC for loose connectors(drag test with a male connector).....

Has the car been scanned for codes?