Tach shows random rpms and bounces all around

[turbo90gsx]

As said in title, if i give it a little throttle, say to 1500rpms or so, it will shoot up to 4k and bounce back and fourth between 4k and 3k(just the tach, not the motor), then it goes back down. Sometimes when it goes back down, it will try and idle at what seems like 100rpms. i think it might be either the TPS or ISC. anyone know what it is? thanks

 

[90AWDTalon]

As said in title, if i give it a little throttle, say to 1500rpms or so, it will shoot up to 4k and bounce back and fourth between 4k and 3k(just the tach, not the motor), then it goes back down. Sometimes when it goes back down, it will try and idle at what seems like 100rpms. i think it might be either the TPS or ISC. anyone know what it is? thanks

Do you have a '91-'94 ecu in your car?

 

[turbo90gsx]

Do you have a '91-'94 ecu in your car?

You know what... I just might. Would that have something to do with the sparatic tach? It might be a 91 cause i got it from a junk yard car. It had pop up head lights, so I ganked the ecu cause mine was causing problems of its own. Its worked fine for a month or so though. I really want a 90 5 speed turbo eprom, but i can never find one.

 

[90AWDTalon]

Check that out.

Here's some info for you if it is indeed a '91 ecu, http://www.ecanfix.com/~mdhamilton/ecuconversion.html