Surging idle

Drove to work the other day and while I was sitting in the parking lot truck was in park my idle would go from 600rpm up to 900 rpm and then drop back down. No codes are showing up. Just trying to figure out if this is normal or not.

 

Errr if this is a new, noticeable symptom for your vehicle have you looked under the hood for a quick inspection?

Air filter clean
Air boot from box to T body sealed(no air leaks)
Maf sensor in place and clean?

 

Accessories like power steering, A/C, and others will cause an engine RPM increase to operate them.

 

Along if set to defrost.

 

I experienced something sort of similar over the summer. Consistently happened on cold start, 8+ hours after shut off, when temps were over 70F and only in gear. No surging in neutral or park. Always went away if I revved the engine in neutral. Never experienced it if I allowed the engine to warm up.
I wasn’t really sure what was happening (high octane fuel, my tune, mechanical issue…) and sort of threw a handful of cheap fixes at the issue.
Cleaned the throttle body/MAF sensor and haven’t experienced it since, but we also never got back up to those “high” temps

 

Throttle Body may need cleaning. It is easy to do, with a cloth and throttle body cleaner. If that is the problem, after you clean it, your idle will run high until you drive it some and it relearns.