Having never done this before and with a faster than normal idle speed, I decided to check out the TPS. First, I checked it out while it was installed on the car. But, then after I could not remove the bottom TPS screw to make the adjustment, I ended up removing the entire throttle body.
You will need a set of feeler gauges that you can purchase at Autozone for a few bucks. Make sure to take with you the Haynes or BGB, so that you know which sizes you will need for this (.35mm=.0128in & .59mm=.0232in), as they will have quite a few different sets available.
1) Highlighted below is the TPS, which is connected directly to the throttle body of course.
2) Remove the TPS plug, by prying up on the clip, and pulling the plug straight out.
3) Insert the appropriate feeler gauge into the throttle assembly.
4) Measure the resistance in the TPS according to the BGB or Haynes manual. Here’s the table you should use.
If you fail any of the tests, then you will need to adjust the TPS position. It is just like a distributor, on how it ‘pivots’ along 2 screws for adjustment. Here’s a pictures of the throttle body out of the car for clarity on where the TPS screws are:
Adjust the TPS until it is within specs of the above table.
In case you need to remove the throttle body to get to the TPS, or if you would like to clean out the throttle body itself, here’s a walkthrough
1) Disconnect the negative battery cable. Remove the AFM and it’s associated hoses. You should then be at the below picture. (This pic is actually during the install, so expect yours to be very dirty if you haven’t done this ever, like me.)
2) Remove the below circled hoses, bolts, etc. Consult the BGB or Haynes for more details:
a) Green – Remove the VTV and it’s hoses, take note of which way the VTV is situated, black side to the rear of the carb) Red – Air hose and clampc) Yellow – 4 coolant hosesd) Orange – There’s 2 coolant hoses w/ clamps here behind the VTV. Both are full of coolant, so be sure to be ready for some spillage as you remove them.e) Purple – Remove the throttle spring and the adjustment rod. The rod is removed by just prying and spinning it out.f) Blue – Now you can remove the two 12mm nuts and two 12mm bolts that hold the throttle body in place. There’s also a 12mm bolt that connects the yellow-circled hoses to the TB, which you cannot see in this pic. You will need to remove it too.
4) Clean the Trottle body itself, carb cleaner works wonders. Make sure to scrape off all the old gasket that was there.
Here’s a pic of the TPS removed.
5) I took this time to replace the TPS screws with some allen wrench bolts that I purchased at Home Depot. The writing on the package is “4mm x 12mm cap screw socket”. Also used two 4mm washers. Should be alot easier to adjust now with the TB on the vehicle.
6) Here’s just a pic of the adjustment with the TB outside the vehicle
Once you are happy with the results of the TPS, the installation is opposite of the removal. Use some RTV as the gasket between the TB and the intake manifold or buy a new one from Toyota.
After you get everything back together and fire up the car, you may need to burp the coolant system because of the hoses you needed to disconnect. Also, adjust the idle speed screw. I actually, had a very bouncing idle after the reinstall, which I thought was air in the coolant system. After about an hour of burping the car and still no better results, I adjusted the idle speed screw and that fixed the problem. I believe the car runs better now, it is able to idle after warmup at 1200rpm. The TPS is definitely in a different position than it was before.