I’ve had this problem for a while now. When my car is warmed up, and I’m at a stop light or just idle when parked, the engine struggles to stay on. The RPM stays under 1000 and fluctuates a lot, usually between 500 and 700. It’s stalled few times, but mostly it is annoying.

I read around and decided to replace the fuel filter. Been two days, but so far no change. I will try the oil filter next, but I was hoping someone could give me advice on the most likely culprits so I can try and at least diagnose it and go from there. Oh, and there are no check engine codes. Everything checks out so far.

  • has it actually ever stalled when idle? My jeep's idle RPM is usually between 700 and 500 - and that thing is really hard to stall. What did the idle RPM of your focus used to be? Did anything change, or did the RPM just drop one day?
    – Sponge Bob
    Commented Mar 8, 2013 at 5:28

2 Answers 2


I'd put a vacuum leak or a failed idle speed controller of some type at the top of my list of suspects. Not familiar with a Focus, but those are common problems that can cause those symptoms as a car ages.


Just had this issue with my 2011 Chevy Cruze. The PCV valve under the valve cover was stuck open.

I also had issues with the Idle Air Control on a previous Neon. This was a bigger problem when the A/C was on.

But, vacuum leak would be on the top of mt list for things to check.

If the car has a MAF (Mass Airflow Sensor) it may need to be cleaned (especially if you have a K&N or some other oiled element filter). You can get some MAF cleaner at local part store and just use the manual to determine how to remove it. Spray it off and let it go.

A quick fix may be to remove the positive batt cable and try to turn the car on a few times. This will drain the power and the car will need to relearn everything (including it's idle settings).

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