> i have cleaned the idle speed regulating valve but how can i check whether it works or not?

You can check visually by removing it and applying power to it..

Or you can press the button on the small diag box 3 times in a row (engine not running!). This will start a test-sequence of most of the actuators on the engine and you can listen for the idle control valve to make a buzzing noise. Should be a 'smooth' sound without any hickups.

> If the ecu had a fault and needed replacing would it give a fault code?

Depends if it can detect such a fault or not.. But usually is the ECU pretty much the last thing that's broken in most cars.

> My car has 94000Km, should i replace the oxygen sensor with a new one?

First check for the vacuum (and also exhaust) leaks you mentioned. This would cause the engine to run lean and can cause the ECU to think that the sensor is broken.

At 94.000km it may need replacing, but you can check by attaching a high impendance voltmeter to the sensor wires (the data signal, not the heater wires :) and see if the sensor gives a voltage or not and if the voltage fluctuates between 0 and 1V. If it's not doing anything then the sensor may indeed be dead.

You will probably destroy the sensor when trying to remove it.. Even on relatively new cars they tend to get really stuck in the exhaust..

> so i assume they checked the valve clearances and other stuff i cannot do my self

Valve clearance usually isn't a big issue on these engines. You will notice if the clearance becomes too big that it starts to sound a little more 'tappety' when running.

I think they officially only have to be checked/adjusted at 120.000km or so.

> Should i check the catalytic converter whether it has gone bad?

Only after you have fixed the oxygen sensor problem (wether by fixing vacuum leaks or replacing the sensor..) can you really tell if the cat is OK or not.

An exhaust gas tester from an MOT station should then be able to tell you if it's looking OK or not.

> What would you recommend that i should do?

One step at a time :)

First I'd go over the engine and it's hoses/wiring/connections and check them all out. Check the wiring, clean connectors (and spray with some contact spray and sealant), check hoses for leaks or leaky clamps, lubricate, etc.

After that I guess you have 2 problems:

- idling
- oxygen sensor

These should not really be related, although a bad oxygen sensor could (in theory) screw up your idling on a hot engine. The sensor is dis-regarded for the first 5 to 10 minutes after startup, so if the idle problem is immediate then it does not have an influence.

> I guess the clicking noise is there but i cant be 100% sure

Do you have a Haynes manual? I think they have the pinout for the throttle-pot in there, so you can theck the resistance and also check if the switch closes properly if you release the throttle.

Bye, Arno.