Take the 2-minute tour ×
Motor Vehicle Maintenance & Repair Stack Exchange is a question and answer site for mechanics and DIY enthusiast owners of cars, trucks, and motorcycles. It's 100% free, no registration required.

I have a 2003 Ford Explorer that hasn't been idling well lately. It normally idles around 800 or 900 rpms, but lately it will slow down to 400 or 500, then burst up to 1100 and repeat the process again. It doesn't do this all the time, maybe only half-time. Occasionally the rpms get so low that the engine dies, but that only seems to happen when I'm turning AND braking at the same time.

I don't have any idea what's causing it, and I really haven't even pinned down a common variable for when it happens. It seems to have started with the cold weather, but even then I couldn't tell you for sure.

Does anyone have any ideas or suggestions before I take it in to the shop?

share|improve this question
    
Is your car due a service? My first thought would be something like a MAF or lambda sensor, but if it's due some service items (Plugs, leads, air filter etc) then it might be worth doing that first. How does it run when you're above 1000rpm? And is it diesel or petrol? –  Dan Jan 1 '13 at 18:05
    
An air leak would be my other guess –  Dan Jan 1 '13 at 21:52
    
I'm not sure if it's due or not. I just bought it in August, and these problems are just showing up for the first time. Above 1000 rpms it runs perfect. –  jdickson Jan 2 '13 at 16:16
add comment

2 Answers

up vote 4 down vote accepted

It might be the intermittent failure of an idle speed solenoid. They go by a bazillion different names and have just as many variations. For example:

  • Fast Idle Valve
  • Idle-up solenoid
  • Accessory Valve/Solenoid
  • Auxiliary Air Valve
  • Et cetera...

It may also be, as noted in your comments, an air leak somewhere. Seeing as how it works fine above a certain RPM, I'd be willing to bet it's an idle speed solenoid of some type. Typically air leaks result in poor mileage.

share|improve this answer
1  
Thanks Nick, you nailed it. After a good cleaning with throttle body cleaner the fluctuations stopped, but the RPMs were still low. I finally replaced it (Ford calls it the IAC valve, stands for idle air control valve) and it's been running like a champ ever since. Easy fix too. –  jdickson Feb 27 '13 at 22:38
add comment

Check for vacuum hoses that are torn, disconnected, or missing. You brake system relies on vacuum and an idle speed that is affected by holding the brakes probably has a weak vacuum. You can get a cheap gauge at an auto part place that will quickly tell you if you are in spec.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.