Hi, I installed a BBK 58MM throttle body in my 97 Z-28 and after I installed it, my car idles at 1400-1600 RPM. I let it sit there and idle for I'd say around five to ten minutes to "relearn" it's idle, but it constantly stays in the 14-1600 RPM range. It doesn't back off no matter how long I've been driving it. It idled completely normally before the new TB, I'd say from 8-900 RPM. I tried slotting the holes on the TPS and moving it back and forth, but nothing happened there. I tried moving the throttle stop screw, and nothing happened. Is there anything you guys think may be wrong? The car's running rich as all hell too, but it's been doing that since I bought the car, so nothing new there. Thanks for your help.

 

I would check for proper TPS and IAC operation with a scan tool.

Why not fix the rich condition before adding a larger TB? You are just adding more variables to figure out.

 

I know you slotted your TPS sensor already, but you probably have to slot it more. Or you may have broken it, i had one break real easy when i slotted it. You also need a voltmeter b/c the point of slotting it is so that you can move it and change the voltage. you also may have slotted it the wrong way (did that once also) I can't remember the numbers b/c it has been so long but i think the voltage needs to drop below .8 volts or something. if you can't get it low enough, slot it more. when you get it low enough, tighten the screws. just tryin to help ya out.

 

Thanks for the info, I'll hopefully get it scanned sooner or later. I slotted the TPS both directions so I could rotate it either way, and no matter which way I rotated it, the idle didn't change. In addition, I routed the slots almost to the full length of the ears of the sensor, so I don't believe it's a matter of whether it's slotted far enough or not. I also took the sensor off of the throttle body an rotated it manually. When I turned it forward, the idle would go up, so I would let off and it dropped down to what sounded like normal idle, but then quickly went back to 1500 RPM. I guess now it's just a matter of making the time to investigate it farther. Thanks for your help, and if anybody has any more advice, let me hear it.

 

My BBK 58mm would stick a little and keep the RPMs a little high. I just added an extra throttle return spring and now no more problems. While its running just reach over and try to close the blades more to see if they are sticking open.

 

Rotating the TPS sensor isn't going to alter the idle speed, unless you get the voltage above 1.0V, and that means the PCM will think you still have your foot on the throttle (and will also give you a code and SES light). Seems like maybe the engine is getting air from some other source than the IAC passages. Did you put new gaskets on the TB-to-manifold, and bottom plate-to-TB connections? Are you sure all the bolts/screws are tight? Did you put the seal back with the TPS sensor? Are the blades nice and close to the bore of the TB, or is there a gap around them?

 

The blades aren't really sticking open any, I pushed back to close it more, and there just wasn't any budge. Injuneer, you've given me some things to think about. I did use all new gaskets between the intake and the TB, as well as the bottom plate to TB. As far as the seal to the TPS, I'm not absolutely sure, I'll have to go back and check. Thanks for your help, you've most likely pinned the problem, it's just up to me to find out for sure.