Ford Focus ZX5 Turns off at Hard Stops

I have a 2005 Ford Focus zx5, which has been a great car for me so far. I live in DC, and traffic is insane. Over the last year or so, maybe once every other month, my car has turned off when I come to a hard stop (usually braking suddenly at a light/pedestrian walkway). This is my first time owning an automatic, and it’s just as if my car had stalled out. The radio will stay on, etc, but the engine dies and I have to put it into park and re-start it.

The RPMs have seemed to fluctuate a bit as well, usually on start-up or on hot days.

So far I haven’t been motivated enough to get it taken care of, since it happens so infrequently and things seem great otherwise, but I’ve got some free time coming up and want to make sure I’ve got an idea of what I’m looking at when I take it in.

Any thoughts on what could be causing this?

The problem might be with a faulty Idle Air Control valve.

This component is located on the throttle body. When the engine is up to operating temperature and idling in park/neutral, open the hood and take the handle of a screwdriver and tap on the IAC valve. If doing this causes the idle speed to change replace the IAC valve.


I’m assuming the check engine light is not on. As mentioned above, could well be the IAC. Here’s another idea though. If you notice the car doesn’t idle as well as it used to – when you get back home after your commute park the car in the driveway, leave the engine running, and listen carefully to the idle – is it a smooth idle? If not, you may have unmetered air getting into the engine creating a lean condition. A vacuum leak is the most likely cause.

Thanks, Tester and GeorgeSanJose. I’m going to try both of those suggestions tomorrow, and will let you know!
There are no lights on. A friend said that perhaps the computer is still registering an error code which could in fact be read, but because it’s happening with such infrequency it hasn’t triggered a light? I thought about taking it in to Auto Zone and getting it read just in case…but also wasn’t sure if this actually was a plausible chain of events.