Well, the other day im coming home from work and get a CEL, so I have the code checked, and its P1133. I check here, and folks say its an O2 Sensor, so i replace the one on the manifold, no problems there. The next day to work, no issues. Afterwork, i took the car out for a little run, no problems either, when when i come back to work for a few minutes, after i start the car, it idles a little erratic. It'll rev high for a second or two, then almost stall, this happens when the car is rolling or not, after a few minutes it'll go away and sometimes it'll come back after a restart. The issue seems random, as if its an intermediate vaccum leak, but i double checked twice and nothing. My dad thinks its a coolant temp sensor, because the day i had the CEL, i hadnt driven the car since that morning, and when i cranked it up, it was pretty close to operating temp (cold day, been atleast 6-7 hours later). The only other thing i had done was top off my coolant, as it was slightly low from a leaking cap, which was replaced a while back, just hadnt gotten to topping it off (probably unrelated). Ive taken the negative off the battery, actually for a while (installed an AEM Short Ram earlier today), and the problem still exists. My dad also says i should to my thermostat, as on cold mornings, it takes quite a while to warm up (maybe 5-10 minutes of driving, with a cold heater). I changed the coolant less than 3-4k miles ago, using Universal as well. Any ideas JBO?