JUST BOUGHT GSX. TACH suddenly not working

[diputz42]

sup all. i just bought a 5sp '92 gsx on saturday. bone stock driven by a woman.

PROBLEM 1:
it was driving fine the first two days, but this morning when i started it to go to work, the tach read 0 at idle. for the first 5-10 minutes, the tach seemed to go up to match wheel speed. then later on, the tach started coming closer to engine speed, but i could still tell something was off. when i revved it up to what sounded like redline, the tach only read about 5k. i got to work and when i turned off the car, the tach read 500rpm. i left it for abotu an hour and came back to check on it and it still read 500rpm. I just took it out for a spin and the tach seems to be working to a point. except it feels like its reading 500rpm under what the engine speed sounds like. yet when the car is shut off, its reading 500rpm again.

has any1 had a problem like this before? is there a ways to fix it? any help would be great!! THANKS.


PROBLEM 2:
when in gear and the throttle is let off, there is some kind of grinding/sanding noise coming from the engine as the rpm slowly decline.


PROBLEM 3:
when gunning it, there seems to be some kind of noise coming from the rear passenger side of the car. IMO, it kind of sounds like a window is cracked and air is passing it. or something similar to that.

btw, if anyone reading this is in the East SF Bay Area, maybe you could help me with this car.

 

[diputz42]

i just went back out to test the car. the tach seems to be working fine now... i dont know why it would have done that tho. any1 else have this happen to them b4?

 

[JessesTalon]

2. could be your driveline shimying around and making a weird ass noise

3. could be exhaust leak, or is it coming from inside the car you think?

 

[RossY]

The sensor that connects to the tranny for all your tach/speedometer stuff came loose on my car once. I wish i had video of it cuz the speedometer would just wig out. From a complete stop the the speedometer would shoot up to 100 in about 1/2 a sec then eventually settle at the right speed. Sounds to me like there may be something wrong with either the sensor or tranny which is located in the area where the noise was coming from.

 

[Gigaah]

Even if your speed sensor was tore up or broken it "should" read 0 when the car is off.
The grinding noise could possibly be your speed sensor grinding on the tonewheel in the transmission giving your problems.
Tach or ECU could be messed up too off should = 0 as with all other gauges.