Last post on Feb 10, 2013 at 5:07 AM
You are in the Toyota Corolla
What is this discussion about?
Toyota Corolla, Sedan
#237 of 238 Re: RENTED A 2010 COROLLA LE BEFORE PURCHASE [terceltom]
Jan 09, 2012 (8:49 am)
I read the measurements for the Corolla and Civic and they're similar; we have an 06 Civic. I cannot get comfortable in the 10 Corolla; my back hurts, my shoulders hurt, even my hands hurts and I'm only 5'5". Something is just not right. It's like I'm squeezed into a tiny box. We've had two previous Corollas and never had this problem.
#238 of 238 Re: 2010 Corolla idle problem [jeffostema]
Feb 10, 2013 (5:07 am)
You're not off your rocker, Jeff. I have a 2010 Corolla LE (1.8 L, auto) that behaves in exactly the same manner. I purchased it used about 16 months ago, and have noticed the same issue with rough idle. I drive this car on the highway generally so it's a minor annoyance, but here's what I've observed:
With A/C on (in summer months): Issue never appears. Idle is consistently 800 to 900 RPM.
With A/C off: Idle is normal (800 to 900 RPM) unless the brake is depressed enough to turn on the brake lamps. I backed up to a reflective surface so that I could observe the brake lamps, put the car into [D], and set the parking brake to keep it from moving. While depressing the brake pedal very slowly, the idle consistently falls to a shuddering 500-600 RPM as soon as the brake lamps illuminate. When the pedal is released slowly, the idle returns to normal as soon as the brake lamps go back off. Turning on the headlamps causes an immediate return to normal in the idle speed with the brake depressed.
Discussion: The engine control unit (ECU) certainly controls idle speed, probably in a quasi-closed-loop fashion. The ECU knows if the A/C compressor is operating, if the brake is depressed, what gear the transmission is in, and so forth. On the Corolla the ECU must also be reading the state of the headlamps. This car is also equipped with vehicle stability control (VSC), which is essentially an augmented 4-channel ABS system (probably powered by an electrical hydraulic pump). My guess is that there is either an unaccounted for errant/ signal wiring path, engine load from the VSC system, or firmware defect (or wrong calibration constant) in the ECU that is leading to this trouble. The engine is properly compensating for load factors such as A/C and headlamps on, but failing to maintain idle with A/C off and brakes on. I've seen others mentioning this about related Toyota models, so I'm guessing it's more common that you think. Goes to show you that there's a lot more happening under the hood of your car than the average shade tree mechanic could even dream of 20+ years ago.
Concerns: (1) Idle dropping low enough to stall is a safety issue in city traffic. (2) Low idle speed is not healthy for an engine, and could impair lubrication if the oil pressure is consistently falling below acceptable levels.
I've got some local control systems experts in KC that I can consult with...I'll bring this to them to see what they think.