The so-called "unintended acceleration" problem, which has pushed Toyota beneath an unwanted spotlight, still leaves lots of questions.
In my view, unintended acceleration means the vehicle accelerates (throttle plate opens) with no input from the driver. As compared to an accelerator or throttle plate sticking or hanging up. In a case like that, the driver has accelerated (depressed the gas pedal) and then released the pedal, but the throttle plate does not return to its fully closed position. These are two different conditions.
The initial recall involving insufficient clearance between the gas pedal and floor, causing the pedal to catch on certain design floor mats, is an example of mechanically sticking or hanging up. The throttle plate was never moved towards the open position without a command from the driver's right foot -- it just did not return to the closed position when the foot came off.
Now here's the tricky part. The vehicles in question use an electronically controlled throttle body assembly. So instead of a throttle cable mechanically connecting the accelerator pedal to a spring-loaded closed throttle plate -- there's an accelerator position sensor at the pedal, which sends information to the engine control module. The ECM deciphers this information and sends the appropriate throttle plate position command to the throttle body assembly. The throttle body assembly uses an electric motor to move the throttle plate open and closed accordingly.
Toyota, after adding a second recall, more vehicles to the recall list, and stopping sales on affected models, has now determined a secondary cause of "unintended acceleration". In addition to the floor mat issue, the gas pedal assembly itself has now been tagged as a cause -- and parts are on the way.
My question? Is it still a mechanical failure causing the pedal to physically stick and not return, or is it an electronic fault where the accelerator position sensor is outputting a dangerous "open-throttle" request to the Engine Control Module -- causing a true unintended acceleration condition.
Love to hear some thoughts on this one.
Here's the illustration Toyota has released with a statement on their proposed gas pedal fix.
They are concluding it was mechanically sticking, not an electronic signal error.
The fix is still a little unclear going by the illustration, but according to Toyota it involves "a friction device in the pedal designed to provide the proper "feel" by adding resistance and making the pedal steady and stable".
The repair: "A precision-cut steel reinforcement bar will be installed into the assembly that will reduce the surface tension between the friction shoe and the adjoining surface".
Sounds like Toyota service departments will be working non-stop for the next few months to perform the modifications on the millions or cars involved in the recall.
Hopefully this will conclude the problem, but media reports indicate certain driver's still claim they experienced the "unintended acceleration" condition without the gas pedal sticking.
It's looking more and more like the gas pedal defect was indeed a case of the pedal sticking mechanically, and not returning to the full off-throttle position in certain instances.
Toyota Executive Vice President Shinichi Sasaki said in a statement: "electronic problems in the cars were not responsible for the defect in the gas pedals, as some have alleged."
Due to the immense media exposure, the related drop in sales is expected to exceed that of a typical safety recall.