Badin vs. Coldwater
Zoo mommies and babies
2009 China Fashion Week
Straight Talk
The case of the weird throttle
Saturday, March 07, 2009
Wheels: Brad from Texas writes, "My Mazda3 died at a light on the way to work this past week. It was running kind of crappy, with a fluctuating idle. After the engine died, it would barely run, and then just crank. I had it towed home as I try to do most of my own work on my vehicles.
I went through checking stuff and replaced the spark plugs. Poking around, I pushed on the throttle butterfly and it wouldn't move (drive-by-wire car). I took it off and cleaned it with throttle body cleaner as it was all gummed up and stuck. It runs just about perfect now so apparently the butterfly was so gummed up, the engine couldn't move it.
So all is good, except the on/off throttle transition is very abrupt, driving me crazy when I'm cruising at 40 mph. Maybe there is an air bypass that is still clogged? Also it now idles perfect, even when the air conditioning kicks on, but when moving and pushing in the clutch, it idles at 1500 RPM until it comes to a stop, and then drops to 900 RPM or so. Any ideas?"
Halderman: The vehicle is equipped with an electronic throttle control (ETC) system. The throttle plate should easily move open and closed from the home position by a spring. The electric motor in the throttle body assembly forces it closed and forces it open from that position using a signal from the computer. Basically, I think it is a bad throttle position sensor that is causing the wrong signals to be processed. About the only thing to do is to replace the assembly.
Wheels: Gary of West Carrollton writes by e-mail, "Can you help me out on the heater fan for my wife's 1999 Honda CR-V? The heater will only blow at high speed. On other vehicles over the years I have owned that had this problem, it turned out to be that a couple of resistors in the fan control circuit or on the fan itself burned out. In a couple incidents, it turned out that the wire came loose and, one other time, the solder joint let go.
Anyway, I want to check the fan but do not know where the resistors are located or if that is how the fan system works on her car. Can you help me out?"
Halderman: The resistor (usually just one, but they are in series) burns out and therefore the blower works only at high speed. The resistors are always downstream from the blower so that the air from the fan will keep the resistors cool. I think you can get to the assembly by removing the glove box and then looking for the multiple-wire plug to the resistor pack. I'll see if I can find out any more. The resistor usually fails when the motor draws too much current, so I would also replace the motor. Sorry, but this will ensure a lasting repair.
James D. Halderman is an ASE-certified master technician and
a member of the Society of Automotive Engineers. Submit your automotive care questions to Halderman via e-mail at jhalderman2@juno.com, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.
