UK Car Repair: Stalling when breaking, throttle position sensor, vauxhall astra

Question
I wonder if you could help to solve this mystery. I have a Vauxhall astra 1.6i automatic, 2002, 67000 miles, petro, 16 valve. The car runs well except it can stall unexpectedly at junction/roundabout/traffic lights when the car slows down. It feels as though the car is running out of petro and suddenly the battery sign on the dashboard comes on and then the engine is totally cut off. When the engine is off, I lost the brake as well. I have spend about £350 in total in the vauxhall dealer service centre, but the problem still exist, from about 15 times per week down to about 5 times per week.

Answer

Takes a few tries to restart?
Belches smoke once it has?
Maybe hard to start in the morning?
Noticed a weird sucking sound under the dash?
Fuel economy gone to the dogs?

Well, a few things could be wrong. However; I have had one other person ask about a car like yours and after some research of my own I have found that beyond the normal mechanical issues there is a weak link in the system. My question to you is... Did the dealer replace your ECU?
From the price you quoted me it sounds like they haven't.
I would check into it, it appears to only be referenced to the 8 valve version. However, the likelihood of the computers themselves being completely different is nil, just separate programming.

The issue with a rolling stall in an automatic car is usually referenced to three systems. One would be a car with a locking torque converter that is not unlocking. Another would be throttle air control issue ether stemming from a bad idle air control valve or a dirty throttle body. The third issue would be on cars that are designed with a fuel cut deceleration. That is when you remove your foot from the gas; the engine shuts off the fuel supply to the engine to save burning excess fuel in a situation where none is needed. That system is affected directly by the Throttle position sensor and if the throttle position sensor has a worn spot at the lower aria of the sensor and the computer is unable to compensate for the lack of signal it will stall. As a matter of interest to the brakes, do they get very hard or do they stop working all together and go right to the floor? Also, do you smell any funny smells coming from the vehicle? Get back to me and we will try getting to the bottom of this issue.

John