Why is it called the throttle body ... and does it do more than control airflow?
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Playsinsnow
Member
- Nov 17, 2012
- 9,727
A dirty throttle body will cause you to be sluggish and result in poor performance and mpgs. Or worse. To add to what it "controls".
Throttle body sounds better than accelerator butterfly assembly?
Throttle body sounds better than accelerator butterfly assembly?
blazinlow89
Member
- Jan 25, 2012
- 2,088
Its the body that contains the throttle. Literally. Think of it as an aluminum structure (the body, can be steel or plastic as well), which contains a valve (in our case a plate on a single pivot, or a butterfly valve).
Some throttle bodies may have a MAP sensor built in as well as multiple vacuum lines and ports for various things. Ours also contains the throttle position sensor, which is just a potentiometer that tells the PCM, the position of the valve in the throttle body. Some things life the MAP sensor and vacuum lines may be on the actual intake manifold, however the TPS will always be on the throttle body.
Some throttle bodies may have a MAP sensor built in as well as multiple vacuum lines and ports for various things. Ours also contains the throttle position sensor, which is just a potentiometer that tells the PCM, the position of the valve in the throttle body. Some things life the MAP sensor and vacuum lines may be on the actual intake manifold, however the TPS will always be on the throttle body.
Just more details for the curious. The butterfly valve is moved by a stepper motor. And the TPS is actually TWO potentiometers, and the PCM compares their outputs to make sure it has an accurate reading of the butterfly valve position. If they ever DISAGREE from a bad sensor or broken wire, the PCM goes into REP mode so you can limp home, but that's designed so a single failure won't result in WOT behavior that can kill you. Same thing for the accel pedal. Two sensors for redundancy.
Playsinsnow said:
Pretty sure any sticking of the throttle valve during normal operation would throw a code. As Bill mentioned the PCM checks the valve position against the Pedal position Sensor. Most issues involve starting and idling where there is a slight buildup of gum in the bore. Never seen someone complain of MPG or performance issues involving a throttle body unless something is seriously wrong.
There is only one line connected to the throttle body. It is for the evap recovery system. It goes back to the canister.
blazinlow89
Member
- Jan 25, 2012
- 2,088
the roadie said:
Did not know we had dual potentiometers, good to know I guess. Also I hope the stepper motor they used for the TB is better than ones in the guage cluster.
blazinlow89
Member
- Jan 25, 2012
- 2,088
AtlWrk said:
I need to start using purple for sarcasm. Knowing GM some stuff would not surprise me though.
Texan
Member
- Jan 14, 2014
- 622
the roadie said:
I retired about the time the "other" car company was having sudden acceleration problems. I was able to watch the testimony before congress
about the problems. Going from memory, it was stated that the two signals from the pedal to the TPS were both going from like 1 volt to
5 volts from idle to WOT. I got out my TB shop manuals and noticed that my Chevy had two signals that went in opposite directions. One went
from 1 volt to 5 volt+/-, while the other went from 5 volts to 1 volt. This made more sense to me for drive by wire. I have often wondered if
this may have been part of the problem. The other car company was/is secretive about what was in the computer memory.
IllogicTC
Member
- Dec 30, 2013
- 3,452
Texan said:
The NHTSA got to investigating when the Toyota accelerator thing got big. NASA even helped investigate. They determined that there were two separate incidents, both mechanical - one was the floor mat catching the accelerator, the other one was the accelerator itself getting stuck. Driver error was also cited in some cases - I know people would get a bit panicked when their car began suffering a runaway condition, but the ignition switch would have magically made it go away. If you turn the switch off, the fuel pump stops running, the injectors stop, spark plugs no longer receive fire, the throttle returns to closed or near-closed. It may damage the vehicle but it'd save lives. Or even just putting it in neutral - it may cause engine damage if one didn't think to reach down and check the gas pedal after getting stopped, but again you could just coast to a stop (while retaining power steering and vacuum boost to the brakes.
This is stuff they don't teach in driver's ed for some reason, but really they should. In a modern car this should be basic knowledge, it can never be assumed that everything will go exactly perfect. Car companies spend millions in design and get it right most of the time. But even space agencies, dumping BILLIONS into vehicle design, have still had failures.
Envoy_04
Member
- Jul 1, 2013
- 749
Shoot, driver's ed nowadays is a waste of time. They put you in the car, you drive (usually in a nice non-crowded area) for a little while in perfect conditions, taking turns with the others in the car, then go back to school. You learn the very basics of if your car is safe (checking the oil is as in-depth into car stuff as you go) and the "rules of the road" are about all that is tested on. Most students take the class for the lower insurance rates, and have had their license for at least a year before they even have the class. Plus the teacher is usually one of the sports coaches, so the class is about as laid back as you can get. It is an utter waste of a class period unless you are a complete novice to everything that has to do with driving and you have no ability to learn by watching others.
I learned to drive on an old S10, and drove it all through high school, and the mechanical throttle cable would sometimes bind where it went through the firewall (yes, there actually were cars where the throttle was a mechanical device!) and cause quite an exciting moment. This usually happened when the throttle was being aggressively applied and down in the area of travel that it didn't see often. You'd have to tromp the pedal a few times to get the cable freed up and be on your merry way. A few years ago when the other company had their crisis I didn't see the big deal, I thought a sticky throttle was normal!
I learned to drive on an old S10, and drove it all through high school, and the mechanical throttle cable would sometimes bind where it went through the firewall (yes, there actually were cars where the throttle was a mechanical device!) and cause quite an exciting moment. This usually happened when the throttle was being aggressively applied and down in the area of travel that it didn't see often. You'd have to tromp the pedal a few times to get the cable freed up and be on your merry way. A few years ago when the other company had their crisis I didn't see the big deal, I thought a sticky throttle was normal!
