Audi 90 wont turn off or start - 1990 Audi 100

Hi Tox
The hall sensor on your 1987 Audi 90 is fitted in the distributor body,You can purchase the hall sensor on its own,Or buy a secondhand distributor.

get areal car audi is for lazy losers worst car ever

Check the clutch interlock switch on the clutch pedal arm. You can jump across this switch to defeat the interlock function as a test to verify the switch is the problem. Also try pushing the clutch all the way to the floorboard when turning the ignition to start. If the switch is good, then check for power at the starter solenoid and relay.

It sounds like you have a head gascet fault, if the water hoses are highly presurised with back pressure when car is running and you are lousing water, creamy coloured oil then these are all symptoms.
some audi's have platic water pump fins that deteriorate too this also could be a fault,
A pressure test on the cooling system should conferm what exactily is wrong.

key may need reprogrammed

It sounds as if the timing is out

I had that same problem on a 1990 audi 90.

Turns out the radiator was leaking, so the coolant kept running out causing the temp light to go on. as a temporary fix, you can keep topping up the coolant, but otherwise you are going to need to get that radiator fixed. by the way, audi 90s have TWO radiators; in my case it was the smaller radiator that had gone. 

new radiator later, and it was fixed. unfortunatley, my temp gauge has never work...

it's an electric fan that turns on only when needed --by a temp sender in the rad (at about 92˚ - 105˚ F)

Check for voltage at the coil or ignition module. If there is dc voltage, then check for ac voltage at the coil.
Do It Yourself Diagnosis and Repair

immob problem??