omaha90

So I installed the new O2's as well. It is still throwing a bad Coolant Temp Sensor code. And it still runs rough with a rich smell. It does not come on right away. It waits a while sometimes. The sensor is brand new. I have tried to clear the codes, but when I short the two pins furthest from me nothing happens. Do I have to turn the car off and then on to clear?<ul><li><a href="https://forums.audiworld.com/9080/msgs/249300.phtml">Previous Post</a></li></ul>

4Driver4

Usually the bad Coolant temp sensor means the T-stat is gone. The ECU assumes that all mechanicals are working correctly, so when it sees a low temp reading, it assumes that the temp sensor is bad even though the reading is correct. The ECU does not "consider" the possiblilty of a bad T-stat, it just knows that the reading is lower than expected.

I bet the t-stat is physically broken. It should be obvious when you pull it apart.

Julian_B

2nd that, prolly stuck open

DanAudi90

the sensor. Look in Bentley manual. It will give you resistance of the sensor at 2 temperetures. Pickup a multimeter and test it at these temperatures.
I would say you have also other issues. Even in cold weather the car is not supposed to run like crap. Mine runs smooth as soon as I start it even at 20F.
Did you check vacuum system?
Does your car warm up at all when you leave it running and if so does it idle normally when it warms up? Touch the heater cor hoses.
If your lower rad hose gets equally warm as the upper hose (put your hands on them when you start the car and wayt to feel it warm up) then chances are the t-sta is stuck open. If your lower hose stays cold while the upper hose (or heater core hose) is warming up then the t-stat should be fine.
If you ask me test the sensor AND wiring before going for t-stat. Not that its a big deal to replace it, but with the T-belt on its much harder to pull out the cover. If you replace t-stat be carefull not to break the rear T-belt cover when you are pulling on the t-stat cover. I learned it the hard way. $65 for a new cover.

Good luck

omaha90

I have not replaced the the t-stat. I did not even think of that. I will give that a try tonight and update later. Thanks again for all the hel guys!

YucatanAudi

I recently replaced mine, because the engine wasn't fully heating up. The old one I took out looked completely normal and was closed when I removed it. But, the new one now lets the engine fully warm up. Obviously, sometimes, the 'innards' of an old thermostat can be broken without anything showing. Glad I replaced mine. Mileage is up.

omaha90

Did you have rough idle and acceleration problems?