TPS Problem
Thread Starter
Junior Member
Joined: Oct 2009
Posts: 19
Likes: 0
From: Westminster Maryland
Car: 87 Trans Am
Engine: 350 TPI
TPS Problem
Ok so I've been having some idling/stalling during acceleration problems and I had been reading about Throttle position sensors and it sound like it was my problem (No engine error code was up then), I replaced the TPS and now the error code is up and I cant get the car to run worth spit. I've read alot about tuning them and all but I need a straight answer. I have an 87 tpi 350. any help would make my work alot less difficult. thanks
~
Aaron
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Aaron
Junior Member
Joined: Sep 2008
Posts: 88
Likes: 0
From: Nebraska
Car: 54 Chevy Sedan Delivery
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3.73 posi
Re: TPS Problem
When you replaced it did you get it set correctly, also maybe reset your iac and idle adjustment.
Senior Member
Joined: Apr 2004
Posts: 587
Likes: 0
From: Calif
Car: 75 Vette
Engine: 406 TPI
Transmission: 700 R-4
Axle/Gears: 373
Re: TPS Problem
Here is how to ajust your IAC and your TPS
Idle Air Control
Tools needed:
Torx bit # T-20
Paper Clip
Small Punch
Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' pins.
Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.
Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.
Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).
If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait 5 minutes. This will clear the ECM of all trouble codes. Re-connect the battery and drive the car for 20 minutes to allow the ECM to relearn your driving style.
Throttle Position Switch (TPS)
Tools needed:
Digital Volt-Ohm-Meter (VOM)
Jumper Wires (make your own)
Auto Xray Scanner (if available) will eliminate the need for VOM and jumper wires.
Turn on ignition, but don't start the engine.
With a scanner: plug in the scanner and read the TPS voltage. It should be 0.54Volts +/- 0.075Volts
With VOM and jumper wires: disconnect the connector from the TPS. Using your jumper wires, make a connection allowing some room for the VOM terminals to contact the jumper leads and read the TPS voltage.
If out of spec, loosen the two screws holding the TPS to the throttle body, and slightly rotate the TPS up or down, reading the voltage until it comes into specification. Tighten screws. Using the throttle lever, rotate the throttle to WOT (wide open throttle). The TPS voltage should be over 4.0 volts. Close the throttle again, and then slowly open it to WOT, observing the voltage reading. It should increase progressively and in a linear fashion. If it sticks or jumps or falls off at all while doing this check, that could mean a bad TPS switch and could be a cause of stumbling and driveability problems.
After setting the correct voltage, turn off ignition switch. Remove jumpers/scanner and reconnect the TPS connector as required.
Idle Air Control
Tools needed:
Torx bit # T-20
Paper Clip
Small Punch
Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' pins.
Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.
Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.
Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).
If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait 5 minutes. This will clear the ECM of all trouble codes. Re-connect the battery and drive the car for 20 minutes to allow the ECM to relearn your driving style.
Throttle Position Switch (TPS)
Tools needed:
Digital Volt-Ohm-Meter (VOM)
Jumper Wires (make your own)
Auto Xray Scanner (if available) will eliminate the need for VOM and jumper wires.
Turn on ignition, but don't start the engine.
With a scanner: plug in the scanner and read the TPS voltage. It should be 0.54Volts +/- 0.075Volts
With VOM and jumper wires: disconnect the connector from the TPS. Using your jumper wires, make a connection allowing some room for the VOM terminals to contact the jumper leads and read the TPS voltage.
If out of spec, loosen the two screws holding the TPS to the throttle body, and slightly rotate the TPS up or down, reading the voltage until it comes into specification. Tighten screws. Using the throttle lever, rotate the throttle to WOT (wide open throttle). The TPS voltage should be over 4.0 volts. Close the throttle again, and then slowly open it to WOT, observing the voltage reading. It should increase progressively and in a linear fashion. If it sticks or jumps or falls off at all while doing this check, that could mean a bad TPS switch and could be a cause of stumbling and driveability problems.
After setting the correct voltage, turn off ignition switch. Remove jumpers/scanner and reconnect the TPS connector as required.
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