Bingo, that's what your problem is then. ECU thinks the engine is still cool, so it's running on "choke" (old car stuff).
Change the temp sensor linked to the ECU, ask your parts dealer. Not the temp sensor for the dashboard. Whilst you are on that coolant side of things, I would strongly suggest renewing the thermostat and antifreeze. Then once everything is running as it should, change the engine oil and filter,as the engine has probably had too much un- burnt fuel running through the system. Cheerio