HOW TO - Set the TPS (Throttle Position Sensor), Idle &
Marco last edited by
Removal of the TB first to do a compete clean would be a good idea, especially if it's condition is in question. Along with cleaning all the gunk out of the venturi and all of the deposits from the coolant in the bottom half, I especially paid close attention to the idle adjust screw that I removed completely (noting the exact position before removal so that it was returned to the same position) since there was a considerable amount of crusty build-up there that definately was a negative factor. Note that some of the following tests/checks can be done while the TB is removed and on the work bench. This will be completely obvious once you've done it once.
You'll need a good multimeter and a non-electronic one would be helpfull for finding any dead spots in the swept area of the TPS.
You need a suitable jumper wire to go from the TEN to GRD in the DIAG box also (paper clip works fine).
Once the TB has been removed and cleaned, re-install ensuring that the coolant lines to the bottom half are connected and not bypassed (which so many people tend to do and don't realize the negative effects this can have).
This is the small black cylindrical valve at the bottom of the TB where the cooland passes through and measures the coolant temperature so as to adjust the idle accordingly. The colder the coolant the higher the idle should be. As the engine warms up this unit's signal to the ECU will change which in turn will lower the idle gradually. Cold weather users will know this all too well.
Remove IAC connector and check resistance reading with ohmeter. It should fall between 10.7 and 12.3 ohms @ 20C.
Re-connect IAC connector.
TPS Adjust (mechanical)
Detach TPS connector.
Wire Colour & Purpose
P= +5V reference
Y= TPS position signal to ECU
BR= TPS idle switch
BK/DB= sensor ground
Connect ohmeter to 2 bottom pins (BR and BK/DB) and you should get continuity. If not, loosen 2 TPS retaining bolts and rotate until continuity has just barely been achieved. Semi tighten 2 TPS bolts.
Insert .006" (0.15mm) feeler gauge between the throttle stop screw and throttle lever. This should not break the continuity. If it does break continuity, slightly adjust TPS rotation again to regain the continuity. Insert the gauge in and out a few times to verify. (Note, it must be mentioned here that the throttle lever must be travelling the fullest extent possible to achieve a complete closure of the butterfly within the venturi. If it's believed that the idle stop screw is preventing the control arm from travelling it's maximum distance to a fully closed throttle then adjust the throttle stop screw via a 2.5mm allen key. If this was necessary, then the previous procedure will have to be started all over again).
After confirming continuity with 0.15mm feeler gauge, insert a .020" (.50mm) feeler gauge. This should just barely break continuity but completely. If not re-adjust TPS rotation again. Re-confirm by re-insrting feeler gauge.
In essence, continuity on initial connection to TPS.
Continuity with .15mm gauge inserted.
No continuity with .50mm gauge inserted.
Tighten down TPS retaining bolts.
Re-connect TPS connector.
TPS Voltage Check
Ensure no accessories - radio, fan, defrost etc are all switched off.
Turn ignition key to ON and ensure TEN and GRD are jumped.
Connect ground of voltmeter to Negative on Battery.
Connect other voltmeter lead to the Y wire (second wire from top) from the TPS connector (A long thumbtack or needle will be needed to pierce the wire shiething. Then connect the voltmeter lead to the thumbtack/needle).
At closed throttle which you are now at, you should get a voltmeter reading of .1V to 1.1V. Rotate the throttle linkage by hand to wide open throttle (WOT) and record voltages again. WOT voltage should be 2.8V to 4.5V.
If voltage readings are not within specified tollerances, than TPS replacement will be in order.
To make a final check if voltages are within spec, rotate throttle linkage slowly from closed to WOT and back several times observing for any inconsistant fluctuations. This is best done with an annalog voltmeter if available, since these fluctuations will be very difficult to pick up on an electronic voltmeter.
Remove thumbtack/needle and voltmeter.
Re-install all intake items.
Leave TEN and GRD in DIAG box in plave.
Ensure that the timing is spot on.
If engine dies right away, adjust idle air screw to 3 full turns out.
Start engine and allow to engine to warm up.
The ISC if operating properly should have the engine idle fairly high if engine was cold. This would be a good time to confirm that the ISC is doing it's job of stepping down the idle as it gets warmer.
Once engine is at operating temperature, adjust idle air screw to approximately 650rpms. The occasional rev by hand is also good to try to ensure idle returns to 650rpms. Once achieved, shut engine off and remove jumper wire.
Start engine again to ensure idle is at approx 700rpm.
If fine tuning to this idle is needed in the future ensure engine is up to operating temp and that the jumper wire is installed. NEVER ADJUST IDLE WITHOUT TEN/GRD JUMPER WIRE.
Do not rest ECU after TPS adjustment. The ECU needs to learn the new settings. A test drive should assist in that regard.
Hope this made things a little easier.
Thanks to jschrauwen - John of mx-3.com
TPS setting picture reference thanks to Jesta