Changed battery now loss of rpm when ac is on

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Our 04 GMC Envoy XL, will not go above 25 mph. Trans.?

bad dash ground or at battery, check fuses also .

You need to have the throttle body cleaned, make sure both the front side and rear side are cleaned thoroughly. Changing the battery reset the computer to factory default settings which are different than when it operated with a dirty throttle body.

Clean your throttle body for starters. The whine could be a multitude of things, but wouldn't contribute to the loss of fuel. Also, replace your spark plugs with AC Delco 43-103, other Platinum plugs don't work well with Envoys/Trailblazers. Also, probably time for an 02 sensor change, the one upstream in the engine compartment. These things will all help increase fuel mileage.

If you want more mileage...us SEAFOAM in the brake booster, and gas tank to clean the carbon out, but after you run a tank, might as well replace the fuel filter too.

Sounds like ac compressor is dragging.It might be that rpm is to low also.Step on the accelarator and if you have a tach bring rpm up to 700 to 800 in drive which is were it should run with ac on. With ac off rpm should read around 600 in drive.

Clean your throttle body. Once the battery is disconnected and the computer reset, it no longer increases power to make up for a dirty throttle body. Get a $4 can of carb cleaner. If you go to a mechani9c they will tell you that it is the ac compressor.

depending on the motor, all makes and models should ranged no less then 500 rpm and 1500 rpm, the most common idle is about 1000 rpm and 1200rpm.

Yes there is a connection with A/C going wacky and the battery disconnected for any reason, due to poor design. Upon re-connection of the battery, our actuators have a good chance of blowing. Pretty common problem, they should have disconnected Fuses #10 and #28 before hooking the battery back up.

For the person with the loud engine and poor acceleration, the problem is likely the fan clutch. I think it is about 800$ to be repaired.