Throttle Position Sensor
Thread Starter
|
Member
Joined: Feb 2020
Posts: 11
Likes: 0
From: Rochester MN
Throttle Position Sensor
Hey everyone i had another thread up with some issues i have been experiencing. So my truck is a 2000 3.0 flex fuel.. What role does the TPS play in tandem with IAC valve if any and what symptoms are a TPS related issue and will the TPS throw a code. Thanks in advance for your knowledge and wisdom. Mike
Last edited by Thestormman3; Feb 17, 2020 at 09:29 AM. Reason: Typo
The IAC Valve is a control, computer uses it to set idle levels and to hold RPMs higher when shifting(manual) or when speed is over 5MPH, to lower emissions
There is no "feedback" from IAC Valve except engine RPM, computer can set RPM within +/- 3rpm using IAC valve so very accurate setup
The TPS is a sensor, it tells computer what driver is doing/requesting from the engine
No real connection, the TPS and MAF sensors are compared, and computer will set codes if these two sensors are not within range of each other
The IAC and TPS are two devices that need to be Motorcraft or Hitachi brands, other brands don't seem to work well as replacements
IAC Valve is a 12volt solenoid, the computer uses Pulsed Ground(PWM) to control its voltage
After engine is warmed up and idling, you can unplug the IAC Valve and idle should drop to 500rpm or engine may even stall, either is good it means no vacuum leaks
TPS uses shared 5volts from computer, it sends back under 1volt, throttle closed, and 4.5v-4.8v Wide Open Throttle(WOT)
TPS is used to give computer a "heads up" to richen fuel mix for instant acceleration, and to shut off injectors when coasting, saves fuel
At WOT the computer will ignore O2 sensors and feed max fuel for best power
WOT with key on engine off will also shut off fuel injectors, its called Clear Flooded Engine mode, allows cranking the engine to dry it out if it floods, can also be used for testing fuel system
There is no "feedback" from IAC Valve except engine RPM, computer can set RPM within +/- 3rpm using IAC valve so very accurate setup
The TPS is a sensor, it tells computer what driver is doing/requesting from the engine
No real connection, the TPS and MAF sensors are compared, and computer will set codes if these two sensors are not within range of each other
The IAC and TPS are two devices that need to be Motorcraft or Hitachi brands, other brands don't seem to work well as replacements
IAC Valve is a 12volt solenoid, the computer uses Pulsed Ground(PWM) to control its voltage
After engine is warmed up and idling, you can unplug the IAC Valve and idle should drop to 500rpm or engine may even stall, either is good it means no vacuum leaks
TPS uses shared 5volts from computer, it sends back under 1volt, throttle closed, and 4.5v-4.8v Wide Open Throttle(WOT)
TPS is used to give computer a "heads up" to richen fuel mix for instant acceleration, and to shut off injectors when coasting, saves fuel
At WOT the computer will ignore O2 sensors and feed max fuel for best power
WOT with key on engine off will also shut off fuel injectors, its called Clear Flooded Engine mode, allows cranking the engine to dry it out if it floods, can also be used for testing fuel system
Thread Starter
|
Member
Joined: Feb 2020
Posts: 11
Likes: 0
From: Rochester MN
The IAC Valve is a control, computer uses it to set idle levels and to hold RPMs higher when shifting(manual) or when speed is over 5MPH, to lower emissions
There is no "feedback" from IAC Valve except engine RPM, computer can set RPM within +/- 3rpm using IAC valve so very accurate setup
The TPS is a sensor, it tells computer what driver is doing/requesting from the engine
No real connection, the TPS and MAF sensors are compared, and computer will set codes if these two sensors are not within range of each other
The IAC and TPS are two devices that need to be Motorcraft or Hitachi brands, other brands don't seem to work well as replacements
IAC Valve is a 12volt solenoid, the computer uses Pulsed Ground(PWM) to control its voltage
After engine is warmed up and idling, you can unplug the IAC Valve and idle should drop to 500rpm or engine may even stall, either is good it means no vacuum leaks
TPS uses shared 5volts from computer, it sends back under 1volt, throttle closed, and 4.5v-4.8v Wide Open Throttle(WOT)
TPS is used to give computer a "heads up" to richen fuel mix for instant acceleration, and to shut off injectors when coasting, saves fuel
At WOT the computer will ignore O2 sensors and feed max fuel for best power
WOT with key on engine off will also shut off fuel injectors, its called Clear Flooded Engine mode, allows cranking the engine to dry it out if it floods, can also be used for testing fuel system
There is no "feedback" from IAC Valve except engine RPM, computer can set RPM within +/- 3rpm using IAC valve so very accurate setup
The TPS is a sensor, it tells computer what driver is doing/requesting from the engine
No real connection, the TPS and MAF sensors are compared, and computer will set codes if these two sensors are not within range of each other
The IAC and TPS are two devices that need to be Motorcraft or Hitachi brands, other brands don't seem to work well as replacements
IAC Valve is a 12volt solenoid, the computer uses Pulsed Ground(PWM) to control its voltage
After engine is warmed up and idling, you can unplug the IAC Valve and idle should drop to 500rpm or engine may even stall, either is good it means no vacuum leaks
TPS uses shared 5volts from computer, it sends back under 1volt, throttle closed, and 4.5v-4.8v Wide Open Throttle(WOT)
TPS is used to give computer a "heads up" to richen fuel mix for instant acceleration, and to shut off injectors when coasting, saves fuel
At WOT the computer will ignore O2 sensors and feed max fuel for best power
WOT with key on engine off will also shut off fuel injectors, its called Clear Flooded Engine mode, allows cranking the engine to dry it out if it floods, can also be used for testing fuel system
The computer controls open time for fuel injectors, STFT(short term fuel trim) is a refection of that open time
i.e. computer "knows" its running a 3 LITER engine, in your case, so it "knows" exactly how much air is coming in at any RPM, it uses MAF sensor and air temp sensor to calculate the WEIGHT of that air
Air:Fuel is a WEIGHT Ratio, 14.7:1 for gasoline
14.7 pounds of air to 1 pound of gasoline
14.7 grams of air to 1 gram of gasoline
Gasoline's weight doesn't change much by temperature
But air's weight changes alot, by temp and altitude, which is what the MAF sensor and air temp sensors are for
So computer makes its base calculation for each injectors open time for RPM, then adjusts that for air weight and temp
Computer also must ASSUME normal fuel pressure, it doesn't have fuel pressure sensor
Say it sets open time as 100ms(milliseconds), this is 0 STFT
After running that it gets feedback from O2 sensor
If O2 shows Lean burn computer will change open time to 102ms, adds more fuel, this would show as +2 STFT, 2% more
If O2 showed Rich then it would change to 98ms, less fuel added, -2 STFT, -2%
If computer has to go to more or less than +15 or -15 for any length of time it will set a lean or rich code
Calculations are done on the fly so very very fast
TPS comes into play to calculate LOAD on the engine which effects open time as well, i.e. in neutral with TPS showing 1/4 open RPMs would be say 2,500, but when driving there would be a LOAD so maybe 1,800rpm, so computer would adjust open time for richer mix, and also open EGR valve a bit
A sudden change in TPS, to say 3/4 open throttle, would cause computer to increase open time, +15-20% maybe, for instant acceleration, it would also change spark timing for the richer fuel mix, the MAF sensor doesn't have instant changes, and RPMs do take a bit to catch up, lol, so TPS is needed for computers instant response to driver input
Computer then re-calculates open time for new RPMs and load
i.e. computer "knows" its running a 3 LITER engine, in your case, so it "knows" exactly how much air is coming in at any RPM, it uses MAF sensor and air temp sensor to calculate the WEIGHT of that air
Air:Fuel is a WEIGHT Ratio, 14.7:1 for gasoline
14.7 pounds of air to 1 pound of gasoline
14.7 grams of air to 1 gram of gasoline
Gasoline's weight doesn't change much by temperature
But air's weight changes alot, by temp and altitude, which is what the MAF sensor and air temp sensors are for
So computer makes its base calculation for each injectors open time for RPM, then adjusts that for air weight and temp
Computer also must ASSUME normal fuel pressure, it doesn't have fuel pressure sensor
Say it sets open time as 100ms(milliseconds), this is 0 STFT
After running that it gets feedback from O2 sensor
If O2 shows Lean burn computer will change open time to 102ms, adds more fuel, this would show as +2 STFT, 2% more
If O2 showed Rich then it would change to 98ms, less fuel added, -2 STFT, -2%
If computer has to go to more or less than +15 or -15 for any length of time it will set a lean or rich code
Calculations are done on the fly so very very fast
TPS comes into play to calculate LOAD on the engine which effects open time as well, i.e. in neutral with TPS showing 1/4 open RPMs would be say 2,500, but when driving there would be a LOAD so maybe 1,800rpm, so computer would adjust open time for richer mix, and also open EGR valve a bit
A sudden change in TPS, to say 3/4 open throttle, would cause computer to increase open time, +15-20% maybe, for instant acceleration, it would also change spark timing for the richer fuel mix, the MAF sensor doesn't have instant changes, and RPMs do take a bit to catch up, lol, so TPS is needed for computers instant response to driver input
Computer then re-calculates open time for new RPMs and load
Thread
Thread Starter
Forum
Replies
Last Post
