My Skoda Octavia ambiente 1.6 2001 model has very poor idle problems intermitantly. The rev counter revs up and then drops suddenly un-controllably. It fluctuautes irratically and this is usually associated with high fuel consumption with a great noise. Whenever it revs up (either on motion or in a traffic situation) and I switched off ignition, I find it very very difficult to start the car and this may take up to 10-45mins(or more) to start again with associated fuel smell during consecutive car start. I have cleaned the throttle body by spraying injector/ carb cleaner. When the car engine eventually starts, the exhaust brings out a dusty-smoky and fuel smell with fuel smell which disappears after a little motorway run and the revs get normalized again and at times the irratical fluctuation of high revs continues. I have changed the fuel pump but problem persists.

Please can anyone advise what the problem maybe and how to fix it? Many Thanks in advance

That sounds a coolant temp sensor problem to me 

Yep, coolant temp sensor is the place start. Genuine VAG part only, do not get an aftermarket pattern part.

Edited 29 July, 201312 yr by pauldazzle