TPS Voltage way high
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 24,460
Likes: 7
From: sw Ohio
TPS Voltage way high
I know this is not for a corvette, but the principal is the same and I wont be able to get help anywhere else. I have an '87 Buick Lesabre and the car is running like crap. I've found the culprit, a faulty TPS or so I thought. I checked the voltage and its way too high at idle, then when I give it gas the voltage decreases. Why? Do I have a loose ground or something?
Normal range: (Idle 0.38-0.45 volts) (WOT 4.5 volts)
Mine: (Idle 4.2 volts) (WOT 2.19 volts)
Normal range: (Idle 0.38-0.45 volts) (WOT 4.5 volts)
Mine: (Idle 4.2 volts) (WOT 2.19 volts)
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
I know this is not for a corvette, but the principal is the same and I wont be able to get help anywhere else. I have an '87 Buick Lesabre and the car is running like crap. I've found the culprit, a faulty TPS or so I thought. I checked the voltage and its way too high at idle, then when I give it gas the voltage decreases. Why? Do I have a loose ground or something?
Normal range: (Idle 0.38-0.45 volts) (WOT 4.5 volts)
Mine: (Idle 4.2 volts) (WOT 2.19 volts)
Normal range: (Idle 0.38-0.45 volts) (WOT 4.5 volts)
Mine: (Idle 4.2 volts) (WOT 2.19 volts)
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
You could have the 5v supply wire connected to the wiper arm on the TPS potentiometer and the wrong end of the pot connected to ground. Connected this way, the 5v supply sees the whole pot resistance at idle (5 volts) and at WOT the 5v supply would go to ground (through the hop off resistance which is low) causing the 5v supply to droop to the 2 volts you observe.
The correct connection places the end of the pot to ground that is nearest the wiper in idle and the 5v supply goes to the end of the pot nearest the wiper in WOT position.
Take a look and see if someone forced the connector on the TPS backwards.
The correct connection places the end of the pot to ground that is nearest the wiper in idle and the 5v supply goes to the end of the pot nearest the wiper in WOT position.
Take a look and see if someone forced the connector on the TPS backwards.
Last edited by jfb; Jun 23, 2007 at 07:42 PM.
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 24,460
Likes: 7
From: sw Ohio
The good news is that you guys were right. I checked my wiring diagram and it was the bottom and the middle wire that I should have tested. The voltage was still high so I adjusted it. However, the car still runs pig rich and stalls out on startup sometimes until I get it warmed up. I'm thinking it could be the coolant sensor or the MAF that are causing this...
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