Hey CL
The reason I was setting my TPS is this; Whenever I let go or depressed the gas, there would be 1 jerk. Checked U-joint's, drive shaft, mounts, and the like and all were secure and looked new. So reading threads and researching brought to the conclusion that it was my TPS. I had replaced the TPS 4 months ago but I just set it by having the car idle, and than I turned it this way and that until the car ran as good as I could get it. Now I know that I'm supposed to set it using an ohmmeter, so the jerk I have makes me think it is the TPS that isn't set correctly. Anyway, I have been attempting to set the TPS. I have been using a feeler gauge, (0.016), an ohmmeter, and an old TPS harness so I can access the tabs to test the ohms. I had it all set up with the ignition turned to "on" position. At first, the ohmmeter was just reading between 4 ohms and 5 ohms. The lowest i was able to get it at the time was 3.90 ohms. And it is supposed to be at least below 2 ohms. I wasn't able to get it lower. But than the ohmmeter went all the way to 5 ohm, than came down to 4.74 ohms and would not move. No matter were I turned the TPS, i even turned the ohmmeter off and on again, and it went straight back to 4.74 ohms. Could anybody tell me what's going on that the ohmmeter only reads 4.74 ohms? Any help would be appreciated greatly. This thunk is starting to grow on me...
Thanks in advance!

 

Wow, i guess this thread isn't very popular...Anyway, what I did this afternoon: I just set the TPS to 4.64 ohms. My reason why i did this is because that is what an IS300 on you tube had his set at. I hope that jerk when i depress the throttle is gone now, and I hope I haven't made the bucking/surging thing start. Any knowledge to shed on the thread?

 

Told you it's gonna need a real steady hands and a lot of patience. It won't run right until you get the specs right, or at least you won't be able to eliminate the TPS as the problem.

 

SO the ohmmeter should read open circuit if it's set right? How am I supposed to get it below 3.90 ohms? Thanks for the help Joseph.

 

Nother quick q; what does the feeler gauge do between the throttle stop screw? I didn't notice any difference in ohm readings.

 

In the thread I linked you, there's a chart there, and the most critical part in the chart in setting the TPS is the 3rd and 4th setting which uses the gauge feeler of 0.40mm and 0.65mm. The gauge feeler have different thickness. Depending on the thickness when you insert it between the throttle cable stop screw it opens up the throttle valve. The TPS is very very sensitive when you're rotating it. I'm not sure which way the ohms go up and down, but when you're trying to set it you should be able to tell when it goes up or down, then you go from there what adjustment you should do. You learn as you go. Me myself didn't have any clue what the heck was a TPS when I first got my SC. Lol

 

^^I didn't know what the heck was an SC400 when i got the car no kidding. It was my Dad that said "this is an awesome car!" I saw it was a V8+Lexus and so I had to have it. So I turned the TPS all the way as far as it could go both ways. The highest i could get it was 7 and something ohms. The lowest was 3.94 ohms. So what your saying is, when I am ohm testing the TPS, I have to wait until it reads open circuit? The throttle line has a tiny bit of slack so when i put that feeler gauge in there it didn't do a dang because it was using the extra slack. The bolts on the cable are tight. I will post a picture or video of what i mean tonight if I can. Thanks for the help!

 

The slack on the throttle cable doesn't have anything to do with the TPS or throttle valve. I wish I can take a pic but I hope you're inserting the feeler gauge in the correct location...

 

I am putting the feeler gauge between the (supposedly) the throttle stop screw were the circle is at the on the "trac" cover. I saw a sort of throttle stop screw were the circle is on the TPS. Is this were the feeler gauge need's to go?
Thanks for all the help.

Ima IDIOT. wrong pic,,,,,sorry...

 

Sorry, this is the best picture i could find...

 

Yeah, it's basically the one that opens up the throttle valve.

 

Then I have the right one...it doesn't change the ohm readings when I remove the feeler gauge there.

 

You don't test the sensor while it's connected to the car's harness. I say that only because you mention having the ignition on.

There are two sensors within the TPS. One circuit tells it that the throttle is fully closed. This is the one that is either open or closed circuit with the feeler gauge in place. The feeler is used so that it reports a closed throttle just slightly before it is fully closed.

The other is a variable resistance. This tells the ECU how far open the throttle is. That one should change resistance as the throttle is opened or closed.

This site (about 2/3rds down the page) shows how to test the TPS:
http://soarercentral.com/sc-forum/me...739/33074.html

 

^^^Its the same thing I linked him; https://www.clublexus.com/forums/per...on-issues.html

I just realized, why did you do it with the ignition on ON position? I don't remember needing to have it on ON? Plus, I'm pretty sure I made it clear that you need to unplug the TPS from the wiring harness, you need to do the readings on the TPS terminals directly.

 

So sorry guys, I'm not understanding something... Thanks for the info MooJohn, I didn't know that...

So I wanna ask, why aren't the ohms moving below 3.90 ohms? Or do I just need to let it sit there for a while? I think I'm on to something...