95 civic with a 95 gsr swap. I just had the swap completed. The needle normally with the swap sits in the middle of the gauge. Tonight I noticed the gauge was around 3/4 of the way up on the gauge. I noticed this at a traffic light. As soon as I drove off, the gauge dipped down. It was moving around really weird. I made it home with the gauge was bouncing around.The needle seems to respond to direct contact to gas pedal. In neutral if I step on the gas the gauge dips. I popped the hood. Everything looks normal. No steam or anything. The overflow bottle was at the normal level. The fan wasn't on. The fan plug is connected. The sensor wire to the head is connected looks fine. I few days ago I replaced the ground wire from the valve cover to the body, with a homemade wire/connectors. Could this be the problem? Today I replace the spark plugs didnt touch the coolant system. After it cools down gonna check the coolant level in the rad. Which happens to be new as is the waterpump and timing belt had those replace during the swap.

 

I just returned from a drive. Before I left, I checked the coolant level in rad. it's full. I rechecked the ground wire to the body. It was a little loose. I tightened the wire thinking that was the problem. But no. Gauge it all over the place. Some times it would stay in the middle if I downshifted and raised the rpms. Other times it would show hot and if I let off the gas it dropped. Nothing consistant. This is really pissing me off. I havent checked for bubbles in the coolant. But there was no oil in it.
I'm assuming the green plug with two wires under the distributer is the temp sensor. It has one wire running off of it back towards the ecu. The other wire is grounded right next to the sensor. Is there anyway to test the sensor and the gauge? Can I replace the sensor at the stock location with an aftermarket unit and get a real guage. I see what seems to be a coolant line right in the area. If I can't replace the sensor at the stock location can I tap into the system in this location?