I have a 2000 Chevy Tahoe 5.3 that revs to 1000 rpm when started. Then it increases to 2000-2500 rpm and hangs up when revved I though it was a vacuum leak so I doused the intake in either and found nothing. PS the intake gaskets were replaced. I started checking sensors and the only ones that throw codes are the MAF and MAP sensors. The EGR, EVAP, TPS, and IAC sensors did not produce any codes/changes. When the MAF and MAP sensors were unplugged they produced no changes in how it ran. I unhooked the brake booster vacuum line and let it suck and it stayed at 1000 rpm but as soon as I plugged the line it revved to 2500 and it I released the vacuum it came back down. Currently I am really stumped as to what the problem is please help.

 

For those people that are struggling with this Problem I finally found my solution. I realized if it revs up and hangs up then it is a Idle problem, so I unplugged my IAC valve and pulled it out and extended it so the valve was 1/16 to 1/32 open and reinstalled it. Then I started it with the connector unplugged and my Tahoe idled like it should. So then I pulled the PCM and did a continuity test on the wires (79, 78, 77, 76 in the PCM plug) and found that one of my wires had a break in it which caused my issue. I replaced the wire and the issue was solved. For those who want to replace the wires and connectors look on rockauto they have the connectors u need at a reasonable price.

 

Good find and repair! thanks for taking the time to update on your fix

 

I just had the same problem with my 01 Suburban but it turned out being the TPS, it wasnt giving any codes but when i tapped on it with a screwdriver it idled back down and showed 0% on my snap on code reader and was showing 9% before i tapped on it at idle.