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2007 Ford Taurus 3.0L

posted Jun 15, 2016 18:01:35 by Blake Soper
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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5 replies
cheryl hartkorn said Jun 15, 2016 21:38:22
does the car stall out if you unplug the iac valve?
RassielCotoMedina said Jun 16, 2016 11:32:03
since the a/c compressor was just replaced i would connect the gauges and check the pressures it may be an overcharge or restriction in the system causing the compressor to overload the engine at idle, if the compressor had a major failure and the guy that did the a/c job did not flush the system you may have a restriction somewhere, after that i would go for the iac
Tyler said Jun 16, 2016 23:36:51
IMO, you've proven out the IAC by running the functional test and getting RPM changes as you open/close it incrementally. I really like that test on Fords, suuuuper glad they include it.

I know the compressor is stuffed down low on this engine, but you might try reaching down to the compressor clutch (engine off) and see if you can spin the front plate by hand. Not the belt pulley of course, just the part that's attached to the compressor shaft. You should be able to turn it by hand.

Blake Soper said Jun 17, 2016 02:18:11
I should be getting back to this one in the next couple days I will try all of this and report back.
Blake Soper said Jun 17, 2016 02:34:13
Just got a call from the owner, he decided to put in the IAC himself, from O'Reileys. He says it was a fix and the car is running beautifully. And yes I liked that functional test too. The owner was amazed when he saw it, like it was magic. HA.

Thanks for the input guys!
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