I'm new, and need help, please

[familyman]

I have a '96 Suburban, 165K miles, 5.7L, 1500 series, automatic tranny, owned for 10 years.

What's happening right now is when I start up, the engine revs into a super fast idle for about 5-8 seconds, then idles down to normal. Whenever I stop and put the gearshift in park, it revs really high again for the same duration and then finally settles back into a normal idle. My wife drives it and has reported that the idle will sometimes surge high when she's sitting at either a traffic light or stop sign. There has not been a CES light at all associated with these events.

Does this sound like the idle speed sensor? Something else? Any and all advice is greatly appreciated.

[unplugged]

Surprising that there has not been any DTC info. Have you looked under the hood to see if everything is normal? Loose vacuum line could be the culprit.

[familyman]

Thanks for the tip. I'll look tomorrow afternoon when I get off work. Being new, though, can you tell me what DTC is? Might it stand for "diagnostic trouble code"? If so, I haven't had any codes pulled yet.