| Message |
I see people replace the throttle position sensor on our cars all the time. There's nothing wrong with this, but I was flipping through the FSM and it occurred to me that the TPS is an incredible simple device, and couldn't be impossible to fix.
If you've tested your TPS and you've found dead spots, or inconsistent signals, give this procedure a shot before you spend a buttload of money on a new one.
The first thing we have to do is bust this thing open. It's held together by two rivets and several plastic snaps. The snaps are likely to break, but try to be careful with them so it will reassemble easier.
Use a drill to remove the rivets. Release the plastic snaps towards the rear, and gently pry it open. You'll have to get the "posts" for the rivets to let go, and go back and forth a couple of times to get it to open.
 Here's a closer look at the guts:
 The TPS is made up of two parts: the hard idle switch (as the FSM calls it), and the throttle position sensor. The hard idle switch assembly consists of the rotating red spindle and four spring terminals. When the throttle is closed (idle), the spindle moves the spring terminals in such a way that the upper two make contact, as shown here:
 On a side note, TT TPSs seem to have a "full throttle" switch, as you can see above (opposite to the hard idle switch). Compare this to an NA TPS:
As you can see, there is only one pair of spring terminals. Interestingly, the "full throttle" switch isn't actually used by the ECU, as evidenced by ConZult and NDS (which both lack and signal or indication for this switch), and the FSM:
 Anyways, grab a small wire brush and some isopropyl alcohol and clean the contact points on the spring terminals. As you rotate the TPS, you can see where the terminals meet each other--that's where you clean. Again, this only covers the hard idle switch (and the "full throttle" switch, should you chose to bother with it. Now, onto the Throttle Position Sensor itself.
If you take a peek under the hard idle switch assembly, you can see a very faint "track." There are two brushes affixed to the underside of the rotating assembly that ride along this track. Dead spots are caused by dirt on this track.
Be very gentle cleaning this track; you don't want to break the brushes, or scratch the surface of the track (thus creating a broken connection). Use the thin side of an art eraser to clean the track, then use compressed air (one of the little cans will suffice) to clear away any eraser shavings. This will safely and gently clean the track of any dirt spots. It's also possible for the brushes themselves to become bent or dirty.
If the brushes are actually bent and no longer making contact, you can try GENTLY prying them downward (towards the track) with some needle-nose pliers. But if there's actually something wrong with them, chances are it's just dirt. If you're careful enough, that eraser will work just fine on the underside of the brushes. Otherwise, slip a small piece of paper under the brush to protect the track, and use a small sheet of sandpaper to clean the underside of the brush. Only swipe it "with the grain" to avoid bending the brush. When you're all done, do a once-over to make sure there's no chemicals, metal or eraser shavings left behind, and put the cover back on. If you managed to salvage most of the clips, it should snap together pretty snugly. Otherwise, use some RTV around the outside to create a new seal and prevent the inside from getting dirty in the future.
 Pop it back on the car, and don't forget to make sure everything is within spec. Check out this page for info on testing and adjusting your TPS. I've found the easiest way to "set" the TPS is with a consult-type program, like NDS. At idle, the idle switch should be "ON" and the TPS should read between 0.4v and 0.5v. At WOT, the TPS should read between 4v and 5v. If you're not able to make these planets align (IE can't get the idle switch to turn on unless the voltage is lower than .4v), your throttle body linkage may need adjustment, or the throttle bodies themselves could be dirty. Hope this helps, and enjoy the ride!
 |
 |
HOW TO: Refurbish your TPS - 
