Position Sensor (TPS) Adjustment
NOTE: If you are running Windows Vista as your
laptop operating system
please review this site for how to set up WinALDL to work in Vista.
Now that you've
the TPS following the directions posted elsewhere on the site, it's
time to adjust the TPS for optimal performance using either WinALDL software
or a Digital Voltage Meter as shown below.
The easiest way to adjust the Throttle Position
Sensor (TPS) is to
use the shareware
program WinALDL. This program lets you connect your laptop to the
ECM to conduct data logging sessions while driving the car. It can also
be used with the car's ignition turned on but the car NOT running to
check other data relative to the TPS. Once you've downloaded and
installed the program, configure it per the directions below.
When you first open
WinALDL, this screen will appear. Select the
configuration button. You may see a Com Port error message.
If you do, the next step will address in the error message.
Check the tag on your
ECM for its service number & then scroll through the ECM
Type field until you find that service number. The green
arrow points to the COM Port for your laptop. If you've
selected the correct COM Port, you'll see data scrolling
when the key is in the on position and when the engine is
running. Hit the Exit button on the configuration box.
There are two ways to adjust
Percentage & Voltage Method using WinALDL
Voltage Method using a Voltage Multi-Meter (VOM).
NOTE: The percentage &
voltage adjustments are completely intertwined i.e. when you get the
percentage number within parameter, you'll also have the voltage
within parameter and vice versa. The two numbers are dependent
on each other so if you fix one, you've also fixed the other one.
If you get a "Check
Engine" light error indicating that a TPS failure, it is most likely
caused by not having the TPS driver nut in the correct position.
Adjusting the TPS using WinALDL
With your laptop
connected to the ECM Data Plug, open the WinALDL program and
turn the car ignition to the "on" position but DO NOT START
THE CAR. Select the "Dash" button which will open the Dash
Display (Yellow Arrow). Then select the "Sensor Data" button
which will also show the TPS Throttle Percent position
(yellow block/red arrow). This is done with
accelerator in the idle position i.e. keep your foot off
of the pedal :-) You want the TPS reading in both the Dash &
Display to be as close to zero as possible (-0.3 in
this example). The green arrow is pointing to the voltage
reading which should be close to 0.50 volts. As noted above,
when you have the percentage number correct, the voltage
number will also be correct.
Now press the
accelerator pedal all the way to the floor and hold it there
until the Dash Display stabilizes with the Wide Open
Throttle (WOT) percentage reading. Anything over 80% is
acceptable and in this example it's 92.9% as you can see in
the Dash and Sensor Data display. Again, percentage and
voltage are co-dependant and at WOT the red arrow points to
the TPS voltage reading which should read 4.2 or more. In
this case it's showing 4.31 Volts.
Here's this same car
with the engine running and idling at 900 RPM. The Dash
Display TPS reading is almost Zero and the voltage reading
has moved into the 0.50 volt range.
Adjustment is made by
rotating the TPS driver slightly clockwise to increase
(counter clockwise to decrease) percentage & voltage. You need to back off the driver set screw 1/2
of a turn to
set them properly. As noted above, Do not over tighten the driver
nut. Once the driver is properly
positioned, tighten the Allen screw to lock it in place. If
you get a "Check Engine" light error indicating that a TPS
failure, it is most likely caused by not having the TPS
driver nut in the correct position.
NOTE: Whenever you
adjust your carb idle via the idle adjustment screws, you
need to check the TPS settings.
Voltage method with a Digital VOM
This method is used mostly by the "hardcore"
technician. In this case we'll be taking voltage readings directly
from the connector at the TPS using a Digital Voltage Meter. You
will need a couple of paper clips or pieces of thin solid wire to reach
into the back of the TPS connector when it's plugged into the
harness. This will allow you attach the leads of your Volt Meter
to the various pins for testing. There are three pins in the
connector, 5V, Ground, and Sensor. DC voltage is measured between
pins Sensor (+) and Ground (-). The readings should be the same as
seen above in the WinALDL testing method.
A voltage check across the sensor
(harness plugged in, key on) should show approximately 0.5VDC at idle
and 4.2VDC or more at full throttle. Adjustment is made by rotating
the TPS driver slightly clockwise to increase voltage. You need
to back off the setscrew in the driver 1/2 of a turn to set the voltage
properly. Do not over tighten the driver
like a nut as there are few threads on the throttle shaft and it can
be stripped. Once the driver is properly positioned,
tighten the Allen screw to lock it in place.