HELP!Truck going crazy.
 

Hi folks, I'm here to stump you with a problem on my truck. 2007 Chevy Silverado 4.8 l, 103,000 miles, Auto. I had the check engine light come on last week. I went to autozone to have the code read, it was TPS. Throttle Position Sensor, I couldn't even tell anything was wrong with it. I called the dealership they wanted 161(have to replace whole throttle body) found a website that had it listed for 121, bought it and put it on today. Well, now the engine in Drive will idle down to almost 500 rpm. When in park and neutral the engine revs up to about 2500-2700 rpm. If I stop at a stop sign and then go with out pressing the accelerator it will go by itself, slowly, but it will actually make it to about 20 mph without even giving it gas. But when the truck is in drive and I am driving it, it is fine and I can't tell anything is wrong with it. It does seem like it downshifts a little hard. When in reverse it acts fine until I get up to a couple mph's then it mildly accelerates on its own. Well I went back to autozone and the check engine light is gone but problem is still happening, he said I should have taken the positive off battery while I was doing it. So I took battery cables loose to reset computers and hooked them back up... problem is still there. Any body have a clue what is going on??? Thanks.

I would double check that you got the right part and that it is installed properly.

After changing out throttle bodies you may need to do idle relearn. Unplug the idle air control valve for a few mins and plug back in. When you start it let it idle in park for bout 5 mins. It will seem like it idles really high at first then it will bring it down.

I'm fairly sure I have the right part. I put the old TPS back on and still have the same problem. The Idle Air Control Valve sounds like a good idea, I just gotta find it. I believe I will be buying the chilton manual today to help me not mess things up like this anymore. Thanks

Well I called the dealership today, he said that it may need to be programmed. So I guess I'm going to stick the new one back on tonight and then take it to them tomorrow and see how that works out for me.