Contour Enthusiasts Group Archives Forums General Troubleshooting hesitation with a/c on

Damm axt zetec hesitates when accelerating from a stop. O2 went bad, replaced that. Still doing it. Car drives perfectly with a/c off. Whats the deal? MAF bad or something?

Nope, it's normal. And here's why.

If you turn on the Defrost or A/C (Or anything besides Vent), you'll engage the A/C compressor. The compressor pulley is located on the passenger side of your engine compartment (check your belt routing diagram, it'll show you.). When you turn on one of those HVAC positions, it will need to spin that pulley as well as the other accessories, like power steering, water pump, etc. You'll always feel some kind of hesitation when you turn on your A/C, it's just the compressor kicking in. Also, you might notice that that car may "surge", almost like you shut the A/C off, because the compressor will cycle on and off.

Yeah, I know, it sucks, but at least you know it's nothing wrong Just wait until you had my problems: Failed A/C Compressor, failed tensioner pulley and failed idler tensioner pulley. Grand total of $700, I only had to pay for the pulleys, which were $40

its not just hesitation its also missing or something. Bucking slightly. But no CEL.

Bucking, or "trailer hitching" as it's sometimes called, can be caused by intermittent sticking of EGR valve. Read that recently in an old post when searching for DPFE sensor IIRC.