Upon medium to heavy breaking in firsr gear the engine RPM drops to around 200 and occasiionally stalls.

I'll give you the senario:

Accelerate in first gear to 4000 Rpm depress the clutch and step hard on the brakes...not hard enough for the ABS to kick in. The RPM drops to around 200 and then recovers to 850 - 900. This is a new occurence. The Autometer AFR is behaving as it normally would, so I tend not to think that it is the Mass Airflow Sensor but I may be wrong. Possibly the fuel filter?

Any ideas any one please...

Thanks

 

Could be the little hose under the flexible rubber pipe from the MAF pipe to the turbo inlet pipe. If it has come out, it can cause poor idling.

Have you changed anything in that region lately??

 

Thanks P20SPD

The engine idles fine its just the strange problem when braking, but I will check it anyway.

Any one else with any ideas?

 

If its an early car, its probably worth cleaning the idle speed control unit.

Hold the car at 2000 rpm and squirt half a can of carb cleaner down the pipe that feeds it with air from the main intake pipe.

Because the recirculated oil vapours go through the ISC, they can get gummed up and become a bit jerky in their action.