Throttle Position Sensor Adjustment
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
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 car
b) Red - Air hose and clamp
c) Yellow - 4 coolant hoses
d) 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.