v5 STi
Engine lumpy from cold start, idles at around 800rpm

Intermitant problem over the last few weeks when starting from cold but clears when left idling for a few minutes. Checked fault codes, nothing shown.

Started 2 or 3 weeks back: Car started ok from home, stopped at shop 1 mile away then re-started car,engine ticking over lumpy. Car ran ok after that for a week and a half.
Started the car to go to work two mornings in a row, lumpy idle once again. Cleared when left to idle and temp needle started to rise. Left outside work for 9 hours and starts ok, every day.
Car again ran and started ok for a week but now back to square one. Last two mornings rough on idle but clears when upto a certain temp, runs and idles ok after that.
Thought it might be the cold start sensor but wouldn't it run erratic from cold every time it's started etc.
Any ideas ?

Cheers

 

You could try cleaning the ICV to see if that makes a difference.

 

When was the last time you changed the Lambda sensor? It's probably that if you're still on the original one.

 

as mentioned try cleaning the IDC valve, could be an issue with the coolant temp sensor that causes issues from cold also what condition are your plugs in?

 

Lambda sensor changed not so long ago so hoping it's not that (but i'll check)
I'll clean the IDC valve again just incase. Plugs, fairly new aswell but again, i'll pull them out and give them the once over..
Thought the coolant temp sensor would show a fault though and cause a problem more often rather than now and again.

cheers so far guys.