Chevy Trailblazer Surges 40 to 60 MPH

My 2005 Chevy Trailblazer that surges while maintaining a speed between 40 – 60 mph. I notice mostly while driving on the freeway. But also trying to maintain constant speeds. The surging stops if I let up off the gas pedal right away while driving. I have been told that I may need to change the fuel filter, but then I had another mechanic said that the fuel filter for this Chevrolet Trailblazer is in the gas tank and it was not able to be replaced.

Answer: Yes, there is no replaceable fuel filter for your vehicle. It is part of the fuel pump module assembly. That would not cause a surging condition anyway if it was bad. It could be transmission related, which is called ‘hunting’ and usually occurs at highway speeds when the transmission is in overdrive. If it is excessive, you can also look at things like the air filter, injector cleaning, and possibly needing the throttle body cleaned. All these can affect driveability. If the check engine light is on because of this, you’d need to get that checked out too.

This condition sounds like a possible transmission surge. Have the trans. fluid level and condition inspected. Most large national transmission repair shops will take a test drive for free to determine if trans. or not. Or get the computer systems scanned for codes, and view data to see if infact transmission or engine related problem.

I had a Ford F-150 do the same thing to me. Customer brought the truck in and was doing the same thing you are talking about. There was a problem in the valve body of the transmission.

I have a 2005 trailblazer that did the same exact thing for months, eventually it went from surging one day to losing power at full speed. Dealer said was air filter, trans fluid, and all were changed & I was sent on my way. 2 days later same thing kept happening…..what do you know after somebody finally decided to take me seriously turns out it was the catalytic converter. So needless to say $900 to fix what seems like the same problem to me. Hope yours is a much easier fix but if it persist I would check it out.

Yes. It could be the catalytic converter. A test would need to be done to confirm that. A scan of computer codes may show P0420 catalyst efficiency low.