99 NB Erratic Coolant Temp - Bad Sensor?
 

What could this be? The car hasnt been getting driven much besides around town every few weeks. Didn't try replacing the sensor yet. The car seems to idle normal but with a high temp reading then drops down a bunch after it warms up, afr gets messed up and idle sucks.

https://drive.google.com/file/d/0B85...ew?usp=sharing

Have you tried an OBD2 scanner to try and read the CLT reading that gets sent to the ECU? IIRC CLT gets reported separately from the ECU (on a different wire). If the CLT there is also erratic, (didn't see the video link) it could be a sensor, but also don't rule out a connector. Its possible that a valve cover leak has degraded the wiring at the sensor itself. Its not impossible, but not likely that a CLT sensor has gone out. They're pretty solid.

Also check out your grounds at the TB. On top and on the bottom. I believe the ECU grounds sensors there. Those also ground other things that could be contributing to funny AFRs.

Do you have a re-route? If so you need to drill and tap a hole to ground the spacer. I had this problem with my begi spacer. If you don't drill and tap you are just grounding through the bolts and the connection can be pretty intermittent like that sometimes.

The wiring harness also makes some sharp turns at the back of the intake manifold. Sometimes you'll find a rub spot where one of the wires ends up grounding out. My last erratic water temp reading was related to this . . . I repaired the wire and improved the security of the harness.