When will I get an easy one?
I've got a 2007 Ford Taurus that at idle with the A/C on, the rpms are sporadic, runs rough, almost dies. With the A/C off, there are no idle or drive ability issues. There is a CEL for misfire on during startup, and bank 2 sensor 2 stuck lean (Sorry i did not write down codes).
All the tests I did where when the engine was at operating temp. Fuel trims are normal at idle - under 10%. Upstream O2 sensors are switching normally at idle and with some snaps. Because of these I did not check for vacuum leaks or maf issues. I tried turning the steering wheel and hitting brake to load the engine, and the rpms are stable. There is an rpm flare on start up but the comedown feels delayed. Also with the A/C on when you snap the throttle it takes a long time - 10 seconds for the rpms to return to idle. With the A/C off, everything is fine.
The IAC valve has good powerfeed and ground, and when running the duty cycle is within range (30-40%). With throttle the duty cycle increases and frequency decreases, which is normal. Ohms are 10.30, within spec of 8-13 ohms. I took it out and tried cleaning. Also energized manually, but the pintle doesn't move, I'm assuming it needs vacuum to see it move. I can command the IAC to open and close with functional tests on the scanner, which increases and decreases RPMs.
The A/C compressor was just replaced, and the A/C seems to be functioning normally.
My thoughts are that the IAC may be receiving commands, but sticking or not returning properly. But I'm also thinking that maybe the new A/C compressor is somehow overloading the engine. A new IAC from Ford is $180, from napa $56. I want to be sure before replacing it. Any ideas???
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