Rough idle on warm start.

[graynada]

When the car is warm, ie the temperature gauge is between the stop and 90C, my car idles really roughly. If I am stationary for more than a couple of minutes then the CAT light flashes. This is noticeable from a cold start and having driven about 3 miles or when the returning to the car after a short stop.

When the car is up to normal temperature it is fine. When it is stone cold it is fine. Under any throttle it is fine.

For this reason I have discounted vacuum leaks, dodgy MAF as I guess these would not be so temperature dependent. When pull the codes it is always both lambda sensors showing no activity and random misfires; however I suspect this is symptom rather than the cause.

Can anyone give me any pointers where to start?

From previous marque engines I have worked on I would be thinking of cleaning the Idle Air Control Valve. How does this engine (ABZ) control air flow at idle?

Thanks in advance