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Michael, Ford Senior Master Technician
Category: Ford
Satisfied Customers: 275
Experience:  Ford Senior Master Tech & ASE Master w/14 yrs exp. Served on Ford's Tech Review Panel
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I have a 2004 Ford Taurus SES, my check engine light is on.

Customer Question

I have a 2004 Ford Taurus SES, my check engine light is on. I took it to Advance auto parts and they said it had 2 codes: Idle Air Control Valve, and a Manufacturers Input/Output Auxiliary Sensor. The engine idles real low and is hard to start, but once warm it runs fine, just at a low idle like 600 RPM's. I bought the IAC valve and installed it, it made the engine idle really high at 2500 RPM's. I immediately took it back and tried another one just in case it was defective, only to have the same result. I re-installed my old one and it idles low again. Can you tell what the other sensor is, no other Autoparts store carry it because it is a dealer part.

Thanks in advance.
Submitted: 8 years ago.
Category: Ford
Expert:  Michael replied 8 years ago.

Extrusion man, do you remember the exact codes that you got from advance? I'm not sure what the Manufacturers input/output sensor is, there is nothing called that on a taurus that I'm aware of. Which engine does you vehicle have? There are two possibilities, one is the 3.0L 12V OHV, and the other is the 3.0L 24V DOHC.


Thank you,


Customer: replied 8 years ago.
I have the 24 valve engine. No they did not give me the codes the guy just read it off to me. It only showed 2 faults. the IAC and the MFG Auxiliary input/output
Expert:  Michael replied 8 years ago.

Extrusion man, there are a couple of reasons that you could be getting a high idle after replacing the IAC.


First one that comes to mind is the computer's memory. The powertrain control module (PCM) learns where to have the IAC set for the appropriate idle RPM's. If old IAC were stuck closed the PCM would have the IAC set high. Now that is has a new IAC it may not have learned the new idle setting yet. To set this just disconnect the battery for five minutes and reconnect it. This will clear the memory in the PCM and start the relearn cycle.


Second is the PCV valve. I have seen some of the PCV valves stick and cause high idles. This will set an IAC code because the PCM can not control the idle and assumes an IAC concern. You could have both a bad IAC and sticking PCV. The combination is now throwing the PCM for a loop since it now has a good IAC.


Third is the wrong IAC. Alot of the IACs look the same but have different operating characteristics. If you find that you are not having a memory or pcv issue. I would try an IAC from Ford.


No other possible idle problems come to mind since the IAC has had such a dramatic effect.


Hope this helps, if you have any further questions do not hesitate to ask.