Idle issue

09 Ford Fusion, 5-sd manual, 37k.

For the past week or so I’ve noticed after exiting the highway and stopping at the bottom of the ramp the engine will idle high. When I shift into neutral to wait at the light it idles at about 1,500 - 1,800 rpm. I will slowly drop to about 1,000 rpm and quickly drop from that to 750 rpm which is the normal idle.

When getting off the ramp yesterday I put it in neutral while coasting and not touching the gas pedal, clutch or anything, the idle went from 1,500 to 2,000 rpm.

Driving around town it seems normal, and the car drives normally with no issues on the highway up until I stop.

Any ideas what could be causing the weird idle issue?


If the car is still under warranty you should be asking your Ford dealer these questions.

The car is not under warranty.

The PCM will idle the engine higher while you are coasting in neutral (which you shouldn’t do, wastes gasoline) so that it is ready when you shift back into gear.

Works as designed…

I only coasted in neutral to see what the idle would do. I certainly wouldn’t expect it to raise by 500 rpm by itself.

The car has always gone right to 750 rpm when in neutral stopped. As I said, it’s no longer doing that and is at 1500 - 1800 rpm for probably 15-20 seconds after I’m stopped, then slowly drops to normal.

How warm is the temp gauge indicating that the car is when all of this occurs?


The temp gauge reads as it always has when fully warmed up. The car has the issue regardless of what accessories are on, including heater etc.

Sounds like a problem with the Idle Air Control valve or the circuitry involving that valve.
You might get the vehicle scanned for any codes although it is possible to have an Idle Air fault with no codes present.

Any recent history of any service work being done on the top of the engine; air filter, plugs, etc.?

Nothing has been done recently aside from an oil change 5 or 6 hundred miles ago.

How pricey would a new idle air control valve be if that were the issue?


A lot of IAC valve problems can be addressed with a good cleaning. I don’t know where it is located on this engine or how hard it is to get to. Often an IAC can be pulled off in the space of about 10 minutes, cleaned in another 10 and reinstalled in another 10. If you’re even slightly handy you could look at doing this yourself. Other than that I can’t imagine anyone would ask more than $50 or 100 to inspect and clean. That’s assuming it doesn’t have a bizarre location and/or removal procedure.

I think this model vehicle uses an electronic throttle and the Idle Air Valve is incorporated into that so it’s possible there could be a fault with the electronic throttle controls too.

Get the vehicle scanned for codes and go from there. Hopefully this is not something that would require replacement of the throttle body because these things are generally pretty pricy. At the age and mileage it should not be faulty but you never know when it comes to electronic gee-whiz stuff.

If your idle air control is easily accessible then clean it out and see. There is that sensor in there that looks like a needle and those can get carbon on them and throw everything off. Also google around for your problem and you may find others with this problem and possibly a tsb.

Does it idle hunt, rpm’s jumping around, or does the idle just jump and remain pretty constant?