1999 Pontiac Grand Am, 2.4 engine, non EGR. I just replaced the throttle position sensor, and when I did, I noticed that the throttle body was a little dirty, so I cleaned it. It wasn’t that dirty (in my opinion…maybe the car thinks otherwise), and I did use the proper throttle body cleaner on it. I did not remove the throttle body; just sprayed and wiped off the crud from the bore and the throttle plate while it was on the car. Didn’t touch any vacuum hoses. After putting it all back together, I get a P0507 code, trac off light is on, and the idle speed is acting goofy. Of particular note when I let off the gas completely under about 50 MPH, the engine will bounce between about 1000 and 1300 RPM at 1 Hz or so (.5 seconds at 1k, .5 seconds at 1300). Once I slow the car down, it idles, but a little on the high side. At 30mph or so, it seems to want to hold 1500 RPM and 30 MPH even with me totally off the gas. I CAN use the cruise control, even with trac off light on, but at times it will kick out. On the highway it seems fairly fine, although it kicked out a couple times today. Harbor Freight scan tool shows new TPS reads between 0 and 100% when I move the pedal, so that seems to be correct.

I’m wondering if the cleaning is now letting more air in, and the IAC is still letting in the quantity of air that it was with the dirty TB, so the engine speed is going high? Will this relearn itself? Could something else be going on? Any advice would be appreciated.