how does the idle adjustment work?. the thing beside the throttle body on the passenger side. it has an adjustment on the top and the bottem. is one for cold and the other for hot? i constintly have to re'adjust it eather to low or too high. need help thanks.

 

I think you're referring to the TPS (throttle position sensor). It has 2 bolts, which you loosen so the whole thing can rotate. You should adjust both your TPS and IAC (idle air control valve, the 4-prong connector on the throttle body) at the same time. When they're both adjusted correctly, the computer will control idle speed. See here for how to adjust them, it takes about 10 minutes. You'll need a digital multi-meter -- if you don't already have one, you can get a cheapo one at radioshack or fry's for around 10 to 20 bucks.

https://www.thirdgen.org/tpimod2

 

I'm trying to adjust mine right now and don't quite understand these instructions...
The instruction doesnt say where to check voltage...and seems like it says to do it with the TPS unpluged...how is there voltage when it's unpluged?

Quote:

With VOM and jumper wires: disconnect the connector from the TPS. Using your jumper wires, make a connection allowing some room for the VOM terminals to contact the jumper leads and read the TPS voltage.
If out of spec, loosen the two screws holding the TPS to the throttle body, and slightly rotate the TPS up or down, reading the voltage until it comes into specification. Tighten screws. Using the throttle lever, rotate the throttle to WOT (wide open throttle). The TPS voltage should be over 4.0 volts. Close the throttle again, and then slowly open it to WOT, observing the voltage reading. It should increase progressively and in a linear fashion. If it sticks or jumps or falls off at all while doing this check, that could mean a bad TPS switch and could be a cause of stumbling and driveability problems.
After setting the correct voltage, turn off ignition switch. Remove jumpers/scanner and reconnect the TPS connector as required.

 

You need three jumper wires a few inches long to do the adjustment. Make sure you remove enough material from the insulation so that you can use the volt meter to take the reading. When you disconnect the TPS connector connect one end of the jumper wires into the connector, and the other into the TPS. You take a reading I believe between the top and the middle wire, but I don't remember for sure. It could be the bottom wire and middle one. It has been along time since I did it. It is very easy to figure out. You will get a constant voltage if you take a reading across the rong wires.
Make sure that you set your base timing to the proper setting and your adjust the AIC first, before doing the TPS.

 

Thanks for clearing that up, I kind of figured but maybe someone should edit the instruction because while searching I found several other post with the same question...
I guess us newbs make all you guys tired...lol

 

I am in the process of doing the same thing.
Just replaced the iac and read the same instructions. Problem is is that is
says there is a torx screw on the side of the throttle body. Where is it????
I must be blind. I looked for it and couldn't find it.
Help!!!!

 

The rorx screw is on the driver side of the throttle body. You can access it from the back. Chances are that it is covered with a metal cover that needs to be removed with a punch.
However, you have a 1990 correct? On speed density cars things are a bit different. I don't think that you should try to adjust those. Also the TPS on these cars is not adjustable. TPS voltage should be anywhere between 0.7 volts and 1 volt when the throttle is closed, and over 5 volts when it is open all the way.

 

I forgot to mention the specs. Yeah 1990 gta 5.7 350.
Thanks for the info, I won't try to adjust it. I will test the tps to see if
it is working right. Will let you know.


Thanks again.




craig