Idle Control – Conversion to Later ECU
The early 944 is equipped with a warm-up valve and an adjustment screw on the throttle body that allows the idle speed to be adjusted mechanically.
The later 955 models (from model year 1985 onward) are equipped with an electronically controlled idle control valve. The ECU monitors the idle speed and operates the idle control valve to maintain the specified engine speed.
When converting to a later-type ECU, we recommend also upgrading the idle control system to the later-type configuration.
For this purpose, we have developed a special conversion kit. This kit allows the vacuum hoses to be adapted with minimal modifications, so the later-type idle control valve can be installed and function correctly.
We also supply a 3-pin connector including wiring, which allows the idle control valve to be connected directly to the corresponding ECU connector.
Installation Instructions
You will need to remove the intake manifold.
We do not supply a mounting plate, but the component will be secure enough; a cable tie attached to the existing mounting plate is sufficient.
The hoses are pre-assembled; after connecting them, you only need to tighten the hose clamps.
You currently have an idle control valve with two wires: a 12V connection and a ground connection.
You can check the 12V connection with the ignition on; it must be connected to the red wire. If you do not have a multimeter, you can use a 12V automotive bulb instead.
The red wire then runs to the center pin of the black connector.
This way, the new idle control valve receives power as soon as the ignition is switched on.
The valve is controlled by the new ECU via the blue and green wires.
The blue and green wires must be connected to the main connector (35-pin), at pins 33 and 34.
You will need to test which wire goes to which pin.
If the idle speed rises above 1200 rpm, then drops and rises again, the wires are connected the wrong way around.
When connected correctly, the idle speed should be around 900 – 950 rpm.
The idle control valve has only a limited control range; you can use the adjustment screw by the throttle valve (effectively an air bypass) to bring the current idle speed within this control range.
Keep in mind that the idle control valve takes about 2 seconds to respond.
If you adjust the screw and hear the engine respond immediately (within 2 seconds), the idle speed was outside the control range. If you hear no response, the idle speed is within the control range.
