TPS Help: Proper testing procedure on LT4
Thread Starter
Racer
Joined: Apr 2000
Posts: 254
Likes: 2
From: Four Hours away from Ten Road Courses! VA
TPS Help: Proper testing procedure on LT4
I have a WOT/power loss issue that I think is related to the TPS. My question is: Can you test this sensor properly when it's off the car? If I measure it's resistance on the bench it seems like it works great. I even measured the resistance of the new one I bought - slightly different ranges, but they both work fine?
I happen to have a little two-connector dongle thingy that I used to use on my '86 - it has two wires sticking out of it so you can connect your voltmeter to it. This makes me think that you have to measure this sensor with the car running - is that right?
Before I pierce the insulation on these two wires (I guess??) to test it, I thought I would ask and see what anyone else may have done - thanks!
(BTW, FWIW: I've got a new PCM, Opti, Coil/Module, Plugs, Wires & injectors)
I happen to have a little two-connector dongle thingy that I used to use on my '86 - it has two wires sticking out of it so you can connect your voltmeter to it. This makes me think that you have to measure this sensor with the car running - is that right?
Before I pierce the insulation on these two wires (I guess??) to test it, I thought I would ask and see what anyone else may have done - thanks!
(BTW, FWIW: I've got a new PCM, Opti, Coil/Module, Plugs, Wires & injectors)
Melting Slicks
Joined: Mar 2004
Posts: 2,141
Likes: 2
From: Pittsburgh Pa
I have a WOT/power loss issue that I think is related to the TPS. My question is: Can you test this sensor properly when it's off the car? If I measure it's resistance on the bench it seems like it works great. I even measured the resistance of the new one I bought - slightly different ranges, but they both work fine?
I happen to have a little two-connector dongle thingy that I used to use on my '86 - it has two wires sticking out of it so you can connect your voltmeter to it. This makes me think that you have to measure this sensor with the car running - is that right?
Before I pierce the insulation on these two wires (I guess??) to test it, I thought I would ask and see what anyone else may have done - thanks!
(BTW, FWIW: I've got a new PCM, Opti, Coil/Module, Plugs, Wires & injectors)
I happen to have a little two-connector dongle thingy that I used to use on my '86 - it has two wires sticking out of it so you can connect your voltmeter to it. This makes me think that you have to measure this sensor with the car running - is that right?
Before I pierce the insulation on these two wires (I guess??) to test it, I thought I would ask and see what anyone else may have done - thanks!
(BTW, FWIW: I've got a new PCM, Opti, Coil/Module, Plugs, Wires & injectors)
Thread Starter
Racer
Joined: Apr 2000
Posts: 254
Likes: 2
From: Four Hours away from Ten Road Courses! VA
So now, without the scan tool, I'm just trying to see if there's a way to tell if this sensor is good or not.
Basically: does a proper resistance range on a bench = functional unit on the car?
Melting Slicks
Joined: Mar 2004
Posts: 2,141
Likes: 2
From: Pittsburgh Pa
you can back probe the connector. KOEO preferably. it should start off anywhere from .40 -.60 volts with the throttle closed and go up incrementally to no more then 5.0 volts. with no large skips or drops.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
You don't measure resistance, you measure voltage. Also, you check the voltage with the engine 'OFF', ignition key 'ON'.
According to Golen Engines, you want to set the voltage at .67, which is the voltage reading mine and my son's 96 LT1s at. You will probably have to removed the TPS and elongate the screw holes to allow some adjustability to achieve .67 with engine 'OFF', ignition 'ON'.
Blue TPS wire and a ground are the connections I made to see the voltage.
While your digital volt meter is connected, slowing open the throttle body butterflies with your had while watching the voltage. The voltage should steadily increase as you open the butterflies with NO sudden jumps in voltage.
There are different views on what WOT voltage should be, but it must be over 4.00 volts and I always shoot for a voltage reading as high as I can get it, but less than 5.00 volts. On L98 engines, voltage above 4.00 caused the ECM to go into Power Enrichment (WOT) mode. I assume the same is true for LT1/4s.
Jake
West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!
According to Golen Engines, you want to set the voltage at .67, which is the voltage reading mine and my son's 96 LT1s at. You will probably have to removed the TPS and elongate the screw holes to allow some adjustability to achieve .67 with engine 'OFF', ignition 'ON'.
Blue TPS wire and a ground are the connections I made to see the voltage.
While your digital volt meter is connected, slowing open the throttle body butterflies with your had while watching the voltage. The voltage should steadily increase as you open the butterflies with NO sudden jumps in voltage.
There are different views on what WOT voltage should be, but it must be over 4.00 volts and I always shoot for a voltage reading as high as I can get it, but less than 5.00 volts. On L98 engines, voltage above 4.00 caused the ECM to go into Power Enrichment (WOT) mode. I assume the same is true for LT1/4s.
Jake
West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!
Last edited by JAKE; Nov 2, 2009 at 03:44 PM.
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
There is no testing procedure for the 96. The PCM "learns" the TPS. A scan tool is the best indication of whether the TPS is functioning properly. Do a visual inspection of the butterfly with the pedal floored to see if it is opening fully.
With a scan tool, should read between 0.36 to 0.96 volts at idle and > 4.0 volts at WOT.
With a scan tool, should read between 0.36 to 0.96 volts at idle and > 4.0 volts at WOT.
Last edited by MK 82; Nov 2, 2009 at 06:27 PM.
Thread Starter
Racer
Joined: Apr 2000
Posts: 254
Likes: 2
From: Four Hours away from Ten Road Courses! VA
There is no testing procedure for the 96. The PCM "learns" the TPS. A scan tool is the best indication of whether the TPS is functioning properly. Do a visual inspection of the butterfly with the pedal floored to see if it is opening fully.
With a scan tool, should read between 0.36 to 0.96 volts at idle and > 4.0 volts at WOT.
With a scan tool, should read between 0.36 to 0.96 volts at idle and > 4.0 volts at WOT.
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Burning Brakes
Joined: Aug 2001
Posts: 797
Likes: 2
From: Westminster MD
Have you checked fuel pressure? That's always a possibility when looking at higher-rpm/load issues. You might need to tape a fuel pressure gage to the windshield and look at it under acceleration.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Other than the minimum and maximum voltage readings, be sure to monitor that the voltage increases incrementally as you slowly open the TB butterflies, monitor for NO sudden jumps in voltage.
In my testing, I found that setting the voltage at .67, (engine OFF ignition key ON) resulted in a higher WOT voltage reading, which is a GOOD thing. That way I felt more confident the system is entering Power Enrichment mode at WOT.
As you probably already know, in PE mode, the PCM ignores 02 feedback and resorts to pre-programmed fuel and timing tables.
Jake
West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
