I've got a 91Z-5M that i recently removed the intake and cleaned everything up so it would look better. I did take the throttle body apart and put new gasket in it while I had it apart. When I got it back together I can crank the car and it idles as it should, but when I give it throttle it doesn't come all the way back down to normal idle. It stay maybe 500rpm higher. I can turn the car off and let it sit for a minute and restart the car and it idle like is should, but again soon as the throttle is raised the idle doesn't drop back to where it should be. I'm thinking the throttle position sensor my be bad?

One other question is my tach reads incorrectly all the time. I've heard an aftermarket coil could cause this. The person that owned the car prior to myself put an MSD coil on it, how do I calibrate the tach?

Thanks
Ray

 

try unplugging your throttle position sensor and start the engine. it will throw an engine code but nothing bad will happen. I just had to do this today as well. If your idle doesnt get worse than i would say its the tps. theyre around $35 new

 

The idle isn't bad it just doesn't come down to normal idle rpm