So, the CEL was on so I was pulling the code. It gave me 0103, Engine Coolant Temperature Sensor. Now the RPM meter goes all the way up to 8000rpm, and plays back and forth. After I pulled the CEL, the light was gone. I haven't driven it after I pulled the code, but I think it might come back when I drive. So is the Engine Coolant Temperature Sensor causing the RPM to do that, or what? Is it safe to drive? Heres a video i took. (Sorry it was with my phone, so the video is crap)
http://www.youtube.com/watch?v=PYCE1osKI4w

 

In that video, the car is idling right? It is just sitting there? Well if it is just sitting in one spot, and the RPMs went up that high, I don't hear the engine roaring like it should or the vibrations when the dial went into redline (I've hit redline once on mine accidentially and everything started vibrating). So I'd say youre fine but go check the tachometer sensor?

 

no, the engine is not roaring, or anything vibrating. the RPM just goes that high just by itself.

 

Then driving wise I think you should be fine. I'm assuming you checked the error code using that ECU method right? (I read about it on here, you turn some screw counterclockwise, clockwise, etc. and it makes a series of long/short beeps) If so, I can't see any way that that would tamper with your tachometer. Regardless, I'd go get it checked out.

 

I've also had a failing Coolant temp sensor and a crazy tachometer at the same time. I also experienced frequent stalling due to the failing coolant temp sensor. After changing the sensor the car runs normal, but tach is still crazy. Was told by the dealership that the tach gets its information from the ECU - there is no separate sensor for it. They also said that it's probably the instrument itself who's failing, so nothing to worry about except it's annoying...
Have that coolant temp sensor replaced though before your car also starts stalling!

 

The first VTEC Maxima.. Just kidding, I really have no answer for you. But that was actually kind of a cool video. You shoul have some fun with it, just record the sound of you reving it and sync it to this video, then re-post it on youtube and mess with the 16 year old Honda fan boys :P

 

Since the dashboard gets RPM signal directly from the ECU and your car is idling normally, my bet is on the faulty dashboard. You can try to disassemble RPM meter and resolder all soldered connections.

Good luck!

 

Have you tried tightening up the TAM screw? Also, check the wiring between gauge cluster and ECU.