TPS Voltage @ WOT
Thread Starter
Drifting
Joined: Jan 2002
Posts: 1,606
Likes: 1
From: Las Cruces NM
TPS Voltage @ WOT
I was adjusting my TPS sensor on my 88 L98 yesterday and noticed that my scan tool was only showing about 3.85 volts for wide open throttle. I adjusted the TV cable a bit and got a hair more travel and it now shows 4.33 volts @ WOT. Going by my handy dandy GM shop manual, it seems like it should be 5 volts at WOT.
My throttle blades look like they are opening completely, so there's not a throttle stickage, although there is a small, maybe 1/16" of play in the throttle cable.
Is that voltage normal for wide open throttle or is it time to replace the TPS sensor? Is there a way to adjust the play out of the throttle cable?
TIA
Chris
My throttle blades look like they are opening completely, so there's not a throttle stickage, although there is a small, maybe 1/16" of play in the throttle cable.
Is that voltage normal for wide open throttle or is it time to replace the TPS sensor? Is there a way to adjust the play out of the throttle cable?
TIA
Chris
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Re: TPS Voltage @ WOT (okinawa86vette)
You'll never get a full 5 volts at WOT. :) Its hard as hell to get that and also a good idle setting. With that said from the factory you only really need about 69% for the car's ECM to go into WOT mode. That is only 3.45v on the TPS.
Race Director
Joined: Jan 2002
Posts: 12,261
Likes: 85
From: O'Fallon Missouri
Re: TPS Voltage @ WOT (scorp508)
You'll never get a full 5 volts at WOT. :) Its hard as hell to get that and also a good idle setting. With that said from the factory you only really need about 69% for the car's ECM to go into WOT mode. That is only 3.45v on the TPS.
:iagree: My car was getting 3.5v @ WOT and was running fine. I was able to adjust the TPS to 4.07v and there was no performance improvements.
Burning Brakes
Joined: Aug 2000
Posts: 984
Likes: 1
From: Cincinnati OH
Re: TPS Voltage @ WOT (STL94LT1)
:iagree: :iagree:
Stock mine was only 3.8, with an aftermarket TB after adjusting it to the proper idle voltage it shows around 4.2. In both cases, a scanner showed that both values translated to 100% throttle angle.
Stock mine was only 3.8, with an aftermarket TB after adjusting it to the proper idle voltage it shows around 4.2. In both cases, a scanner showed that both values translated to 100% throttle angle.
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Re: TPS Voltage @ WOT (okinawa86vette)
My '88 GM Shop Manual was also a little misleading on that issue.
If you set base idle (450rpm) TPS at .65Vdc you can likely get a little more voltage at WOT setting.
The advantage of a higher TPS reading is that the ECM will see WOT earlier and even at part throttle it will see more throttle position so will give more spark advance as well as more fuel (when accelerating).
If you set base idle (450rpm) TPS at .65Vdc you can likely get a little more voltage at WOT setting.
The advantage of a higher TPS reading is that the ECM will see WOT earlier and even at part throttle it will see more throttle position so will give more spark advance as well as more fuel (when accelerating).
Safety Car
Joined: Dec 2000
Posts: 3,767
Likes: 5
From: Jacksonville Fl
Re: TPS Voltage @ WOT (65Z01)
If the TPS EVER goes above 4.5V, it sets a code 21 and the car goes into limp home mode.
If the idle voltage goes above .45V, the ecm will think the throttle is opened and will not put the motor in idle mode. You will have an artificially high idle speed.
If the idle voltage goes above .45V, the ecm will think the throttle is opened and will not put the motor in idle mode. You will have an artificially high idle speed.
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Re: TPS Voltage @ WOT (BBA)
If the TPS EVER goes above 4.5V, it sets a code 21 and the car goes into limp home mode.
If the idle voltage goes above .45V, the ecm will think the throttle is opened and will not put the motor in idle mode. You will have an artificially high idle speed.
If the idle voltage goes above .45V, the ecm will think the throttle is opened and will not put the motor in idle mode. You will have an artificially high idle speed.
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Le Mans Master
Joined: Feb 2002
Posts: 7,858
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Re: TPS Voltage @ WOT (Vince Ivanc)
:iagree: :iagree:
Stock mine was only 3.8, with an aftermarket TB after adjusting it to the proper idle voltage it shows around 4.2. In both cases, a scanner showed that both values translated to 100% throttle angle.
Stock mine was only 3.8, with an aftermarket TB after adjusting it to the proper idle voltage it shows around 4.2. In both cases, a scanner showed that both values translated to 100% throttle angle.
Safety Car
Joined: Dec 2000
Posts: 3,767
Likes: 5
From: Jacksonville Fl
Re: TPS Voltage @ WOT (scorp508)
My 87 with 2.59 gear stock TPS was .400 as measured by my Fluke 77B.
If I adjusted it higher, at about .45v, the ecm went into >2%throttle mode and, IAC went open and idle speed went up to 800 RPM, as opposed to teh normal 550 RPM.
Maybe your ECM is calibrated differently?
I do know the 4.5v upper limit will set a TPS failure code in an 87. I saw that this afternoon (had to buy a new sensor).
If I adjusted it higher, at about .45v, the ecm went into >2%throttle mode and, IAC went open and idle speed went up to 800 RPM, as opposed to teh normal 550 RPM.
Maybe your ECM is calibrated differently?
I do know the 4.5v upper limit will set a TPS failure code in an 87. I saw that this afternoon (had to buy a new sensor).
Thread Starter
Drifting
Joined: Jan 2002
Posts: 1,606
Likes: 1
From: Las Cruces NM
Re: TPS Voltage @ WOT (BBA)
Mine was set at .56V which is well within the shop manual's .54 +/-.08V, but I adjusted it to .62V and noticed better throttle response. Either way, the WOT voltages were between 4.0 and 4.25. As long as the computer recognizes that as WOT and doesn't throw a code, I'm happy. I know the throttle blades are open all the way, I just wanted to make sure the computer was giving the right fuel amount.
Thanks for all the input, everyone.
Once again the Forum helped out.
Chris
Thanks for all the input, everyone.
Once again the Forum helped out.
Chris
