2002 Chevy Trailblazer surges on the highway. Tach bumps up 100-200 rpm while occurring.

When was the last time you had the chain replaces or cleaned and lubricated it. A badly worn chain will cause a surge at medium speed and revs. The fact that it occurs when you hit a bump does suggest to me that it is the chain.

idle about 700

2005 TrailBlazer Clacking and Clunking From Rear End ...

? 4:10
https://www.youtube.com/watch?v=HIA151KxImM
Mar 14, 2013 - Uploaded by sameasiteverwas122
2005 TrailBlazer Clacking and Clunking From Rear End ...Trailblazer clunking noise over bumps (the number 1 and 2 ... How To Find Suspension Noises 101 - EricTheCarGuy - Duration: 23:57. by EricTheCarGuy 1,497,067 views ... How to Install a Water Pump: 2002 - 2009 Chevrolet Trailblazer 4.2L L6 ...

Trailblazer Driveline Noises Discovered - YouTube

? 2:27
https://www.youtube.com/watch?v=GLhTUoHWdNM
Nov 4, 2013 - Uploaded by Roland Caston
the Trailblazer has developed some nasty noises. ... loose in thedifferential and the right front strut has torn through it's bushing.... How To Install Replace Front Axle Disconnect Housing 2002-09 GMC Envoy Chevy Trailblazer ... How Much Abuse Can a Trailblazer Take Part 2 : How to Replace a Rear Axle ...

Noise coming from back on trailblazer - YouTube

Replace TPS (throttle positioning sensor) they're a rheostat that eventually burns a wear spot causing that surge.

IAC motor

check fuel pump pressure or clogged fuel filter

The vehicle should have a stored trouble code, go to an Auto Zone they will read the code for free. Usually idles surges are caused by a malfunctioning TPS sensor or throttle position sensor.

Cooling fan RPM signal malfunction. Poor electrical connection - check for rubbed through wire at clutch. Failed fan clutch assembly

4.7? I've had a few of these trucks do this with bad Throttle Position Sensors.

your EGR valve is malfunctioning