Posted on: Thursday, February 16th, 2006, 10:50:14pm
Official C.O.C Contributor
Gender: Male Posts: 23604 Posts Per Day: 3.48
If you have a ticking noise coming from under the bonnet when the engine is idling, chances are it is the Idle Air Control Valve (IAC), also known as the Idle Speed Control Valve (ISC). Circled in red in the pic below.
There are two methods of curing this noise depending on why it is causing the ticking. One reason is it is getting fouled by deposits. These deposits can usually be cleared using an aerosol of Fuel Injection Intake and Carburettor Cleaner. With the engine running, remove the inlet hose to the valve (arrowed above) and spray one-second bursts directly into the inlet of the valve. This can cause the engine to stall if too much is applied in one go. If the engine begins to falter simply wait until it recovers and then continue spraying. How much you need to do this will depend on how fouled up the valve is.
The other reason is that the duty cycles are set incorrectly. You will need to first check that the engine idle speed is 950±50 r/min (with engine at normal operating temperature). If it not within these limits adjust it by turning the idle speed adjusting screw.
To carry out the following checks you will need either a digital multimeter that can measure duty cycles or an analogue, swing needle, type meter. The monitor coupler is located towards the front left side of the engine compartment.
Close up of the monitor coupler.
Next check that the A/F duty is 60±5% (ON duty meter indication) or 8.4±0.7V (using an analogue type meter) when battery voltage is 14V. Ground terminals B (Diagnosis switch terminal) and E (Test switch terminal) and read through F (Duty output terminal). If A/F duty is out of specification you will need to replace the CO resistor (location shown in pic below) or install one if none was fitted (see table).
Recheck idle speed.
Next measure the IAC duty (A/C off) which should be 35±5% (ON duty meter indication) or 4.9±0.7V (using an analogue type meter) when battery voltage is 14V. Ground terminal B (Diagnosis switch terminal) and read through F (Duty output terminal). If idle speed and/or IAC duty is not within limits adjust it by turning the idle speed screw.
To check engine idle speed and IAC duty when A/C is on (with heater blower switch set to max) the idle speed should be 1050±50 r/min. IAC duty should be 35±5% (ON duty meter indication) or 4.9±0.7V (using an analogue type meter) when battery voltage is 14V. Ground terminal B (Diagnosis switch terminal) and read through F (Duty output terminal). If idle speed and/or IAC duty is not within limits adjust it by turning the adjusting screw on the A/C SV valve.
Drop me a PM if you would like to be added to the ClubCappo Member Map. More details can be found here. We now have an official Facebook group as well as a page! See here
Cappuccino Owners Club › FAQ › How to... › Cure the IAC (aka ISC) valve tick (Moderators: )
Author
Cure the IAC (aka ISC) valve tick (currently 2481 views)
Male
Logged
Locked Board