so i shut off my car to put gas in it and when i get back in and start it up to leave the tach is freaking out. it bounces very rapidly about 1k rpm it still goes up when i rev the car. is my tach going out or something else?

 

could be a faulty cam sensor.

 

Well, for starters do you have a CEL or SES? Hows the car drive? any unusual noises or vibrations? Pull the Codes, report back.

 

The tach signal comes from the ECU. I'm not sure how the ECU determines engine speed. Check the FSM Electrical system section, Meters and Gauges there is some trouble shooting information that should be helpful.

I'm assuming your car runs fine and does not have a CEL.

 

one of the sources the ECU uses is the signal from the cam sensor. as i stated. if you have a scan tool or access to one, plug it in and see what the scan tool reads for rpm's. if the rpm's arent going crazy on the tool like they on on your tach, it may be the tach shorting out. if they are doing the same thing as the tach, then one of the engine speed sending units is sending false signals to your ecu.

 

It could be a fault in the connection between the ECU and the tach the trouble shooting section covers how to check that.

 

well my car has never ran good in the 2 months ive had the car and it has had a CEL for about 90% of that time but nothing else has changed since the tach started going out. oh well the last 3-4 weeks the car has been hard to start esp when cold. it turns over fine most of the time but once and a while it it sounds like it kicks back like it tries to start backwards for a few degrees then back foreword again. in the mornings i have to let it turn over for prob 30-45 secs before it will start. i just have not bothered to post about it because i dont really want to know whats wrong right now cuz i barley have the money to keep gas in it.

 

update with codes now i have:

p0325 knock sensor
p0400 ERG code
p1335 crank pos sensor (ref)

the FSM seems to point to both sensors being used while the motor is running. i thought one was used for starting and the other was used while the motor was running?

 

change plugs ....had similiar issues and the plugs helped mega