engine temp out of whack

[c5z28]

I have a 00 z28 (stock) and on long drives on the freeway usually an hour or so the temp gous whacko. It will go from like 209 to 230 in a seconds time and then go back down to the normal temp, it will do this within a few seconds of the last, and yesterday the temp went up to 260 in like 1 second then went back down to op temp, I took it in to the chevy dealer and they said no thrown codes or shit, now I am out 100 bucks for them to tell me they dont fucking know?! I am taking it to infineon tomorrow, it did the same thing one time before I got to the track then everything was fine. Can someone help?

[blk_jaws]

mabye its the ect sensor (engine coolant temperature sensor), like 20 bucks at the parts store.

[2001NBMZ28]

Thinking the same thing, ECT sensor/connector/wiring.

[c5z28]

thanks I need to pick the car up today, where exactly is the sensor located?-thanks

[2001NBMZ28]

Drivers side front of the head, right near the #1 cyl exhaust. Dealer should've checked it during their diagnostics?

[c5z28]

No they didn't I called and asked them, I even talked to the mechanic who worked on it, he plugged it into the computer nothing wrong-ok give me 108 bucks. I asked him if he did a physical search but in short no-soooo done with dealers forever you motherfuckin bloodsuckin asshats. and thanks to you who are tryin to help