I have a 99 blazer that hesitates and does not seem to have power when the A/C is on. It recently had new plugs and fuel filter installed, but it did not help. Any suggestions.
Thanks

 

It's typical for an engine to lose some power while the A/C is on.

 

It should be fairly transparent though.

You replaced the plugs, but how about the rest of the ignition system, namely the wires, cap, and rotor? These are all items that are part of a proper tune up.

How many miles does the truck have? Have you cleaned the MAF sensor or EGR valve?

 

It had 108,000 until it recently had a re-manufactured Jasper engine installed. The only thing that was done was new plugs and fuel filter that I know of.

 

Can you hear a hissing in the dash behind the switch that's louder than normal when the A/C ir running? Does it stumble on WOT(wide open throttle) but idle fine?

Sounds like it could be a vacuum leak?

Check the vacuum ball under the hood and make sure all the vacuum lines are plugged in.

Also, being a Mass Air engine, do you have a K&N airfilter? Over oiling the filter will cause a build up on the Mas Air sensor.

Hope that helps you out.

 

It idles fine. I will check the rest out. Thanks for the info.