Q&A

Pull the spark plugs and check for fouling. replace those that are bad. While they are out, check the compression. If you have low compression, the oil is slipping past the rings and the engine needs to be rebuilt. Ckeck your oil for water. It will show as a cream colored thick foam. Check your radiator for an oily film. All of these indicate your engine needs to be rebuilt. NOTE White smoke is water. Blue/grey is oil. How is it getting into the compustion chamber??????

Change your dang COOLANT TEMP SENSOR---100% will fix your prob---25 bucks---
you could have ignored this bad sensor too long and screwed your Cat...start with sensor-- thank me later.