What should TPS read (volts) when at 0% throttle?
11-02-2020, 02:25 PM
#1
Race Director
Thread Starter
What should TPS read (volts) when at 0% throttle?
Im troubleshooting a high idle
issue (when warm) on my 93
the tb seems against its set screw
already replaced iac valve
i read .49-.50 volts (on tps) when gas pedal released
what should it read? Im wondering if this sensor (the TPS) is dead
sometimes a couple revs will bring idle to where it should be
yes, ive had the TB apart (monoblade) and cleaned it
issue (when warm) on my 93
the tb seems against its set screw
already replaced iac valve
i read .49-.50 volts (on tps) when gas pedal released
what should it read? Im wondering if this sensor (the TPS) is dead
sometimes a couple revs will bring idle to where it should be
yes, ive had the TB apart (monoblade) and cleaned it
11-02-2020, 03:17 PM
#2
Le Mans Master
the 91 manual calls out .50 volts with the throttle closed and near 5 volts at full open throttle.
the 96 manual calls out .36 - .96 volts at idle and greater than 4 volts at wot.
back in the day we used .56 - .60 volts at idle on the l-98's.
at your .50 volts i would say you are there but what is your voltage at wot?
the 96 manual calls out .36 - .96 volts at idle and greater than 4 volts at wot.
back in the day we used .56 - .60 volts at idle on the l-98's.
at your .50 volts i would say you are there but what is your voltage at wot?
11-02-2020, 05:20 PM
#3
Burning Brakes
Get a multimeter. Set to ohms. Probe the two output leads (not volts) of the tps and then manually / slowly move the tps through its range. It should gradually increase. Mine had a dead spot just off idle. It would jump a few k ohms. An analog meter is best but it’s doable with a digital multimeter. YouTube has some vids on it.
11-03-2020, 07:23 AM
#4
Team Owner
Can you set the 93 through IAC Counts? I do that with the 91.
11-03-2020, 11:07 AM
#5
Drifting
Just a note that on the LT engines, the TPS is auto-calibrating as far as ECM/PCM goes. As Deepa mentions, checking the TPS through its range with the resistance setting on a multimeter can check the sensor itself. Volts is fairly useless since the ECM/PCM can compensate for a wide range. The important thing is making sure the actual physical throttle cable is set correctly. If you connect to the car and datalog, you can see what percentage TPS the ECM thinks you have. Set the cable so that you get the full range, and that should be the end of it.
That said, your ABS/ASR module does not calibrate automatically, so technically the FSM calls for you to use a Tech 2 to zero the TPS for it, but that's not related to engine operation.
That said, your ABS/ASR module does not calibrate automatically, so technically the FSM calls for you to use a Tech 2 to zero the TPS for it, but that's not related to engine operation.
11-03-2020, 02:26 PM
#6
Race Director
Thread Starter
Just a note that on the LT engines, the TPS is auto-calibrating as far as ECM/PCM goes. As Deepa mentions, checking the TPS through its range with the resistance setting on a multimeter can check the sensor itself. Volts is fairly useless since the ECM/PCM can compensate for a wide range. The important thing is making sure the actual physical throttle cable is set correctly. If you connect to the car and datalog, you can see what percentage TPS the ECM thinks you have. Set the cable so that you get the full range, and that should be the end of it.
That said, your ABS/ASR module does not calibrate automatically, so technically the FSM calls for you to use a Tech 2 to zero the TPS for it, but that's not related to engine operation.
That said, your ABS/ASR module does not calibrate automatically, so technically the FSM calls for you to use a Tech 2 to zero the TPS for it, but that's not related to engine operation.
When its high idling, I can see a 1% or 2% throttle position (even with foot off the pedal) ...... (from a 'LIVE' datalog either on my laptop strapped into the passenger seat, or my scantool).
Blip the gas (I have a 6spd) a few times and it goes back to 0% again and the idle settles down to 900 RPM or so.
There was a slight probably .002" gap between the throttle horn and the set screw, but i fixed that by hammer my throttle stop towards the front of the car such that there is no gap (at the expense of now not being able to get 100% throttle open, probably 98% now)
It doesnt matter, bc scan tool still shows 1 or 2% throttle position (foot off the pedal).
I did find there is enough play in the TPS (depending on how much I preload it before tightening the 2 allen head bolts).
Ive now set it such that I see a voltage range of .39 volts to 3.70 volts (WOT).
I also removed the 'spongy' orange rubber disk that is in between the throttle body shaft and the TPS sensor body. It seems 'swollen' .
No idea if that is interfering with the TPS sensor's ability to return to 0%
We will see if that changes anything
This is a PITA
Last edited by dizwiz24; 11-03-2020 at 02:29 PM.
11-03-2020, 04:56 PM
#7
Yeah the % throttle angle is also messed up.
When its high idling, I can see a 1% or 2% throttle position (even with foot off the pedal) ...... (from a 'LIVE' datalog either on my laptop strapped into the passenger seat, or my scantool).
Blip the gas (I have a 6spd) a few times and it goes back to 0% again and the idle settles down to 900 RPM or so.
There was a slight probably .002" gap between the throttle horn and the set screw, but i fixed that by hammer my throttle stop towards the front of the car such that there is no gap (at the expense of now not being able to get 100% throttle open, probably 98% now)
It doesnt matter, bc scan tool still shows 1 or 2% throttle position (foot off the pedal).
I did find there is enough play in the TPS (depending on how much I preload it before tightening the 2 allen head bolts).
Ive now set it such that I see a voltage range of .39 volts to 3.70 volts (WOT).
I also removed the 'spongy' orange rubber disk that is in between the throttle body shaft and the TPS sensor body. It seems 'swollen' .
No idea if that is interfering with the TPS sensor's ability to return to 0%
We will see if that changes anything
This is a PITA
When its high idling, I can see a 1% or 2% throttle position (even with foot off the pedal) ...... (from a 'LIVE' datalog either on my laptop strapped into the passenger seat, or my scantool).
Blip the gas (I have a 6spd) a few times and it goes back to 0% again and the idle settles down to 900 RPM or so.
There was a slight probably .002" gap between the throttle horn and the set screw, but i fixed that by hammer my throttle stop towards the front of the car such that there is no gap (at the expense of now not being able to get 100% throttle open, probably 98% now)
It doesnt matter, bc scan tool still shows 1 or 2% throttle position (foot off the pedal).
I did find there is enough play in the TPS (depending on how much I preload it before tightening the 2 allen head bolts).
Ive now set it such that I see a voltage range of .39 volts to 3.70 volts (WOT).
I also removed the 'spongy' orange rubber disk that is in between the throttle body shaft and the TPS sensor body. It seems 'swollen' .
No idea if that is interfering with the TPS sensor's ability to return to 0%
We will see if that changes anything
This is a PITA
11-03-2020, 06:13 PM
#8
Race Director
Thread Starter
Ok an update i found another TPS sensor that i had removed years ago
i have to assume its broken but i cant remember if it really is. (i had a habit of throwing a shotgun of parts at a problem).
either way i installed it and if anything this problem is WORSE now than it was before
it didnt fix the problem
checking reference volts is a good idea
i have to assume its broken but i cant remember if it really is. (i had a habit of throwing a shotgun of parts at a problem).
either way i installed it and if anything this problem is WORSE now than it was before
it didnt fix the problem
checking reference volts is a good idea
11-03-2020, 06:51 PM
#9
Drifting
Yeah the % throttle angle is also messed up.
When its high idling, I can see a 1% or 2% throttle position (even with foot off the pedal) ...... (from a 'LIVE' datalog either on my laptop strapped into the passenger seat, or my scantool).
Blip the gas (I have a 6spd) a few times and it goes back to 0% again and the idle settles down to 900 RPM or so.
There was a slight probably .002" gap between the throttle horn and the set screw, but i fixed that by hammer my throttle stop towards the front of the car such that there is no gap (at the expense of now not being able to get 100% throttle open, probably 98% now)
It doesnt matter, bc scan tool still shows 1 or 2% throttle position (foot off the pedal).
I did find there is enough play in the TPS (depending on how much I preload it before tightening the 2 allen head bolts).
Ive now set it such that I see a voltage range of .39 volts to 3.70 volts (WOT).
I also removed the 'spongy' orange rubber disk that is in between the throttle body shaft and the TPS sensor body. It seems 'swollen' .
No idea if that is interfering with the TPS sensor's ability to return to 0%
We will see if that changes anything
This is a PITA
When its high idling, I can see a 1% or 2% throttle position (even with foot off the pedal) ...... (from a 'LIVE' datalog either on my laptop strapped into the passenger seat, or my scantool).
Blip the gas (I have a 6spd) a few times and it goes back to 0% again and the idle settles down to 900 RPM or so.
There was a slight probably .002" gap between the throttle horn and the set screw, but i fixed that by hammer my throttle stop towards the front of the car such that there is no gap (at the expense of now not being able to get 100% throttle open, probably 98% now)
It doesnt matter, bc scan tool still shows 1 or 2% throttle position (foot off the pedal).
I did find there is enough play in the TPS (depending on how much I preload it before tightening the 2 allen head bolts).
Ive now set it such that I see a voltage range of .39 volts to 3.70 volts (WOT).
I also removed the 'spongy' orange rubber disk that is in between the throttle body shaft and the TPS sensor body. It seems 'swollen' .
No idea if that is interfering with the TPS sensor's ability to return to 0%
We will see if that changes anything
This is a PITA
Last edited by Nomake Wan; 11-03-2020 at 07:00 PM.
11-03-2020, 07:37 PM
#11
No problem with that circuit! I assume it is the same when you start the car and run the engine?
The only reason I ask is because I had the AC high pressure switch/sensor go bad on my 96 and it caused a TPS problem ( engine light and erratic idle). My reference voltage was around 3.7 volts. Little did I know there was a shorted IC inside the switch/sensor causing my problems. It took me a while to figure that one out.
I think the heat from my headers slowly destroyed that AC switch.
The only reason I ask is because I had the AC high pressure switch/sensor go bad on my 96 and it caused a TPS problem ( engine light and erratic idle). My reference voltage was around 3.7 volts. Little did I know there was a shorted IC inside the switch/sensor causing my problems. It took me a while to figure that one out.
I think the heat from my headers slowly destroyed that AC switch.
Last edited by grandspt; 11-03-2020 at 07:42 PM.
11-03-2020, 07:57 PM
#13
Race Director
Thread Starter
No problem with that circuit! I assume it is the same when you start the car and run the engine?
The only reason I ask is because I had the AC high pressure switch/sensor go bad on my 96 and it caused a TPS problem ( engine light and erratic idle). My reference voltage was around 3.7 volts. Little did I know there was a shorted IC inside the switch/sensor causing my problems. It took me a while to figure that one out.
I think the heat from my headers slowly destroyed that AC switch.
The only reason I ask is because I had the AC high pressure switch/sensor go bad on my 96 and it caused a TPS problem ( engine light and erratic idle). My reference voltage was around 3.7 volts. Little did I know there was a shorted IC inside the switch/sensor causing my problems. It took me a while to figure that one out.
I think the heat from my headers slowly destroyed that AC switch.
i know there is an a/c on ‘idle rpm adder’
but its certainly not enough to account for a 2000 rpm idle
11-03-2020, 08:55 PM
#14
Drifting
Does this have anything to do with the new blower setup? Are you running a blow off valve or internal bypass? Is it slow to settle at the ~900 rpm idle after you blip the throttle or does it settle quickly?
Sounds like an issue my buddy had with a procharged 2v Mustang. It was cured with a larger blow off valve. The smaller one wasn't bleeding enough pressure at idle/low rpm and it would supposedly cause the throttle blade to hang up. Especialy when driving around town and coasting to stop signs/lights in gear. He would blip the throttle and it would settle. He never had the problem before but then then he stroked the engine and did pulley swaps more more boost and the problem began.
Sounds like an issue my buddy had with a procharged 2v Mustang. It was cured with a larger blow off valve. The smaller one wasn't bleeding enough pressure at idle/low rpm and it would supposedly cause the throttle blade to hang up. Especialy when driving around town and coasting to stop signs/lights in gear. He would blip the throttle and it would settle. He never had the problem before but then then he stroked the engine and did pulley swaps more more boost and the problem began.
11-03-2020, 09:20 PM
#15
Race Director
Thread Starter
Does this have anything to do with the new blower setup? Are you running a blow off valve or internal bypass? Is it slow to settle at the ~900 rpm idle after you blip the throttle or does it settle quickly?
Sounds like an issue my buddy had with a procharged 2v Mustang. It was cured with a larger blow off valve. The smaller one wasn't bleeding enough pressure at idle/low rpm and it would supposedly cause the throttle blade to hang up. Especialy when driving around town and coasting to stop signs/lights in gear. He would blip the throttle and it would settle. He never had the problem before but then then he stroked the engine and did pulley swaps more more boost and the problem began.
Sounds like an issue my buddy had with a procharged 2v Mustang. It was cured with a larger blow off valve. The smaller one wasn't bleeding enough pressure at idle/low rpm and it would supposedly cause the throttle blade to hang up. Especialy when driving around town and coasting to stop signs/lights in gear. He would blip the throttle and it would settle. He never had the problem before but then then he stroked the engine and did pulley swaps more more boost and the problem began.
wow. Thats good. ill hVe to check this
yes i moved up in flow from a p600b to d1-sc
ive noticed the existing paxton blow off valve doesnt seem to be bypassing as much air at idle as it used to
there may be a spring in it i can modify (it has a screw)
then again im spinning this d1-sc way less at idle vs the p600b . Of course its still bigger
the problems started with the bigger blower
Last edited by dizwiz24; 11-03-2020 at 09:23 PM.
11-03-2020, 09:21 PM
#16
Race Director
Thread Starter
Does this have anything to do with the new blower setup? Are you running a blow off valve or internal bypass? Is it slow to settle at the ~900 rpm idle after you blip the throttle or does it settle quickly?
Sounds like an issue my buddy had with a procharged 2v Mustang. It was cured with a larger blow off valve. The smaller one wasn't bleeding enough pressure at idle/low rpm and it would supposedly cause the throttle blade to hang up. Especialy when driving around town and coasting to stop signs/lights in gear. He would blip the throttle and it would settle. He never had the problem before but then then he stroked the engine and did pulley swaps more more boost and the problem began.
Sounds like an issue my buddy had with a procharged 2v Mustang. It was cured with a larger blow off valve. The smaller one wasn't bleeding enough pressure at idle/low rpm and it would supposedly cause the throttle blade to hang up. Especialy when driving around town and coasting to stop signs/lights in gear. He would blip the throttle and it would settle. He never had the problem before but then then he stroked the engine and did pulley swaps more more boost and the problem began.
its slow to settle to 900 rpm
11-03-2020, 11:46 PM
#18
Drifting
Are you running a MAF or speed density? I believe my buddy's was speed density so he simply unbolted the blow off valve and found that the issue stopped. He then talked to his tuner and a larger blow off valve was suggested.
Not certain on the adjustment. I have never messed with one myself.
I don't know if that is your issue but could be another thing to consider.
Not certain on the adjustment. I have never messed with one myself.
I don't know if that is your issue but could be another thing to consider.
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dizwiz24 (11-04-2020)
11-04-2020, 04:36 AM
#19
Drifting
Looks speed density to me. Not to mention the '93 was speed density anyway. But I don't see a MAF anywhere that would matter in his photo.
11-08-2020, 08:36 PM
#20
Race Director
Thread Starter
Are you running a MAF or speed density? I believe my buddy's was speed density so he simply unbolted the blow off valve and found that the issue stopped. He then talked to his tuner and a larger blow off valve was suggested.
Not certain on the adjustment. I have never messed with one myself.
I don't know if that is your issue but could be another thing to consider.
Not certain on the adjustment. I have never messed with one myself.
I don't know if that is your issue but could be another thing to consider.
well, i yanked the blowoff valve off - such that there was an open hole to the atmosphere in my curved intake pipe right before the throttle body.
it seemed better, at first i thought it had fixed it. then I came to the horror it was still high idling once the engine warmed up
to my disbelief , despite an inch an a half diameter open hole, the car STILL built at least 5 psi boost when driving . Maybe more, but I didnt stay on it. Theres such air force coming out of that hole (when reving), i was worried it could do some damage under my hood.
i wonder if that 1.5” hole is big enough to bypass enough air (to not cause tb blades to hang open)
im now wondering if i should remove the intake pipe and blower belt (to disable the blower) and drive it to see if the issue goes away.
The only thing (controlling idle) that i havent yet touched is the TPS sensor.
Last edited by dizwiz24; 11-08-2020 at 09:11 PM.