Pahari, is your Siena a 1.6?
This thing has been happening in mine for many years. Checked with Fiat and they said its normal. There is apparently some injector self cleaning algorithm in the ECU. If it senses some probable blockage, it tries to send in more fuel to attempt cleaning.
Even if I leave the engine on, it settles down to its usual idling RPM in a couple of minutes.. I have observed that this happens less frequently if I tank up on premium petrol.. maybe because it has cleaning additives?
I would suggest you to try Power for a few days and observe.. |