This is one of several pages designed to help you out in knowing your way around the engine compartment of your Saab 900.
Click on the image for a larger view.
|AIC Valve||Fuel Pressure Regulator|
|NTC Resistor and Fuel Injector||APC/EZK Knock Sensor|
First up, is the (in)famous Automatic Idle Control (AIC) valve. This valve is a motor that keeps the idle steady, and can adjust the idle according to commands from the LH-Jetronic brain box.
At least, that's what it's supposed to do.
After a number of years, they get gummed up. The consensus recommendation is to remove it from the motor (two big hoses, clamp, electrical connector), and spray out the valve with Carb cleaner or similar noxious solution. Let it dry, and spray a little WD-40 in there to lubricate it. Re install. You should be good for another 100,000 miles.
The Fuel Pressure Regulator maintains the fuel pressure to the injectors by bypassing some of the fuel back into the fuel tank. There are several different values for this unit. The stock unit on a turbo is usually replaced by a 2.8 bar, 3.0 bar, or rising-rate unit (available from places like Group 6, Acellerated Response Motoring, etc.). The purpose is to richen the mixture under high boost, helping to give you more power.
The NTC resistor (lower left) is attached to the intake manifold, and penetrates to the water jacket of the head. It tells the LH brain box how warm the motor is, and thus what to do at startup.
The injector (1 of 4) supplies fuel to the motor via a fuel rail. On one end of the rail is the inlet from the fuel flter, on the other is the Fuel Pressure Regulator. All injectors connect to this rail.
The Knock Sensor is a small microphone that communicates with the APC system (in the case of APC turbo cars) and the EZK Ignition system (in the case of normally-aspirated 16 valve cars). It's hidden down below the intake manifold.