1994 Corvette TPS Question??
Thread Starter
Racer
Joined: Dec 2010
Posts: 307
Likes: 4
From: Milford Connecticut
1994 Corvette TPS Question??
Hi, I have a 1994 Corvette and the car hasn't started for almost a year due to some kind of problem. The car had spark and 43lbs of fuel pressure, I gave up for awhile due to work and no time/money. Finally tonight I started to play with it again and the car started, we unplugged the TPS sensor and tried to start the car and it started!!! The car started after cranking for about a minute or two and once warmed up it starts like it should on the first crank. I plugged the TPS sensor back in and the car runs a little rough as did while it was unplugged. I cleared the codes in the computer and the code for TPS came back. I checked the voltage on the wires to the TPS and everything is good. So, my question is...when the car is cold it is very difficult to start but, starts after 2 minutes of cranking and once warm it starts right up. I plan on replacing the TPS sensor but, could there be other issues causing a cold start problem?? Any adivice/experience is appreciated.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
How did you check the TPS sensor?
You need to measure the wiper voltage. It should go from about 0.4 to 4.5 volts smoothly as the throttle is opened. (voltages may differ slightly). Top of the wiper should have 5.0 volts on it and bottom is ground.
Check the temp sensor in the water pump to make sure the wires are connected or not broken. If open or no connection, it will run extremely rich (and quit).
You need to measure the wiper voltage. It should go from about 0.4 to 4.5 volts smoothly as the throttle is opened. (voltages may differ slightly). Top of the wiper should have 5.0 volts on it and bottom is ground.
Check the temp sensor in the water pump to make sure the wires are connected or not broken. If open or no connection, it will run extremely rich (and quit).
Thread Starter
Racer
Joined: Dec 2010
Posts: 307
Likes: 4
From: Milford Connecticut
How did you check the TPS sensor?
You need to measure the wiper voltage. It should go from about 0.4 to 4.5 volts smoothly as the throttle is opened. (voltages may differ slightly). Top of the wiper should have 5.0 volts on it and bottom is ground.
Check the temp sensor in the water pump to make sure the wires are connected or not broken. If open or no connection, it will run extremely rich (and quit).
You need to measure the wiper voltage. It should go from about 0.4 to 4.5 volts smoothly as the throttle is opened. (voltages may differ slightly). Top of the wiper should have 5.0 volts on it and bottom is ground.
Check the temp sensor in the water pump to make sure the wires are connected or not broken. If open or no connection, it will run extremely rich (and quit).
I did not check the actual TPS sensor, I wasn't sure on how to check the sensor. Once I got into the house, I was researching for more DIY info on this forum and I'll check the sensor Thurs afternoon and post results.
As far as the temp sensor, I checked that and it is plugged in and no visible damage to either wire or sensor plug.
It was great to hear the car running after sitting in the garage broken for a year!!!! Hope it starts tomorrow?
Thread Starter
Racer
Joined: Dec 2010
Posts: 307
Likes: 4
From: Milford Connecticut
1994 Corvette TPS Problem?? Video Update
Hi, I added a video today that shows the hard cold start and the scanner tool data view. It appears that the TPS is the problem according to the scanner info, I'm not a expert mechanic so does anyone have input as to what the problem is or something i missed??
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The TPS voltage is WAY off. It should be 0.4. You are seeing 0.04, which is 1/10 of the correct value.
The TPS sensor gets 5 volts from the ECM and the other end is grounded. The voltage you see on the scanner is the center wire. You could have one of several problems. Either the 5 volts is not there or the center wire is open or shorted to ground. The TPS sensor itself could be bad.
Your plan to replace the TPS sensor is heading in the right direction. If that doesn't work, check the wiring. Measure the voltages on the TPS sensor with a voltmeter. The car doesn't have to be running to do this.
The TPS sensor gets 5 volts from the ECM and the other end is grounded. The voltage you see on the scanner is the center wire. You could have one of several problems. Either the 5 volts is not there or the center wire is open or shorted to ground. The TPS sensor itself could be bad.
Your plan to replace the TPS sensor is heading in the right direction. If that doesn't work, check the wiring. Measure the voltages on the TPS sensor with a voltmeter. The car doesn't have to be running to do this.
Thread Starter
Racer
Joined: Dec 2010
Posts: 307
Likes: 4
From: Milford Connecticut
The TPS voltage is WAY off. It should be 0.4. You are seeing 0.04, which is 1/10 of the correct value.
The TPS sensor gets 5 volts from the ECM and the other end is grounded. The voltage you see on the scanner is the center wire. You could have one of several problems. Either the 5 volts is not there or the center wire is open or shorted to ground. The TPS sensor itself could be bad.
Your plan to replace the TPS sensor is heading in the right direction. If that doesn't work, check the wiring. Measure the voltages on the TPS sensor with a voltmeter. The car doesn't have to be running to do this.
The TPS sensor gets 5 volts from the ECM and the other end is grounded. The voltage you see on the scanner is the center wire. You could have one of several problems. Either the 5 volts is not there or the center wire is open or shorted to ground. The TPS sensor itself could be bad.
Your plan to replace the TPS sensor is heading in the right direction. If that doesn't work, check the wiring. Measure the voltages on the TPS sensor with a voltmeter. The car doesn't have to be running to do this.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
The dark blue wire is the wiper (center tap) on the connector to the TPS. As said, you can measure the voltage with just the key turned to the ON position (no engine run).
If you insert a straight pin up into the connector (with connector on) from the rear, (you can feel it stop when it's hits the metal pin) you can then measure the voltage on it directly. Just connect the red positive lead of the DVM to the pin and have someone in the car press the gas pedal or you can do it yourself by grabbing the throttle. (Obviously DVM black to ground).
Use clip leads on pin, don’t short anything to ground and will be able to get a direct reading. Connect first, then turn key to the ON position.
If you insert a straight pin up into the connector (with connector on) from the rear, (you can feel it stop when it's hits the metal pin) you can then measure the voltage on it directly. Just connect the red positive lead of the DVM to the pin and have someone in the car press the gas pedal or you can do it yourself by grabbing the throttle. (Obviously DVM black to ground).
Use clip leads on pin, don’t short anything to ground and will be able to get a direct reading. Connect first, then turn key to the ON position.
