According to some Toyota forums, cleaning Mass Air Flow (MAF) Sensor can fix low idling. At about 85,000 miles my Corolla’s idle speed decreased from 700 to about 500rpm and felt like it was going to stall sometimes after the AC compressor kicked off. Cleaning the MAF sensor seemed to have done the trick and it was a simple procedure that took no more than five minutes.
[update 5/7/14] – Corolla now has 147k miles and the low idle issue returned and was worse than ever. This time cleaning the MAF sensor didn’t help, so I removed and cleaned the throttle body which was pretty dirty and that fixed the problem.
Cleaning the Throttle Body:
You can do a quick in place cleaning of the throttle body without removing the assembly from the car, but this is somewhat difficult. Also, there’s the danger of losing the tb cleaner spray straw inside the tbody assembly or intake of the car. If that happens to you, you’ve got a lot more work to do. Basically a good first step in determining if your car needs to have the throttle body cleaned is to disconnect the air hose and have a look at the throttle body opening to asses how dirty it is. If it’s REALLY dirty (covered in black gunk) then removing it completely and cleaning it while removed is the best option. Here’s a reference picture of what a clean throttle body looks like:
Here’s a video on how to remove and clean the throttle body completely: https://www.youtube.com/watch?v=nKM6t1517AU
- Spray can of electronic components cleaner.
- Philips head screw driver.
[step 1] Locate the MAF sensor on the air filter box in the engine compartment. Disconnect the electrical connector and remove two Phillips head screws holding the sensor in place. Now wiggle it out carefully.
[step 2] Liberally spray cleaner over the visible sensor (but be careful not to touch it with your hands) until any dust buildup has been removed.
If you look inside the bottom opening of the component (where the circular hole is), there is a 2nd sensor deep inside the plastic housing. Spray cleaner into the housing to remove dust from this sensor as well, but be careful not to touch the sensor with the straw of the spray can, it can easily be broken or damaged.
[step 3] Let the MAF sensor dry for a few minutes and re-install.
That’s it. Hope it helps someone else.