today after noon i start my car and i notice low rpm (300 rpm in drive) ,so idecide to adjust the TPS,i loosen the 2 screws and iturn the TPS clockwise but the rpm keeps dropping until the engine died,i turn it the other way and start the engine but the engine died again ,i went back and iturn it all the way clockwise and start the engine but the rpm keeps dropping until i turn the a/c on and it jump up to 800 rpm,after that i drove around for 5 minutes the iturn the a/c off and guess what the rpm stayed at 700 rpm>>>>>my question is do ihave a bad TPS or a bad ECU ?????????? 1995 ls 400

 

First of all the TPS is usually set more accurately than by "ear". Generally they are set by angle or voltage. Also it is an input device to the ECU. The output stage of the idle system is the idle air control valve, and that may be where the problem is. The TPS will set a code, the IAC may not. Have both checked and set properly.

 

you need to use a multimeter to set the TPS properly. If the TPS was bad, normally, the ECU would display an error. (check engine light). If that is not the case, check around the MAF area, it could be something as small as a really dirty air filter, because it you said the car fixed itself after turning the AC on. So i would check around there, and get the TPS properly configured, you cant just unscrew it and turn it completely clockwise or counter clockwise

 

Do you know what the code# is?

 

heres the site

check it out whether you have OBD1 or 2

if you are a 1st gen LS, you look at without OBD2

 

What site?

 

whoops.. here it is

http://www.troublecodes.net/Lexus/

 

thanks to all of you for the fast reply to my message,the next day i drive to the dealer for trouble check and guess what ?dealer work shop was closed for maintenance,so i went to the parts store and order a new TPS ,after waiting for 30 minutes to get the new TPS which cost me 40$ the new one looks diffrent ,when i told the worker that one looks diffrent ,he told me that one is the up graded one,so idrive to the auto electrical shop and asked them to put it in,aftert they put it in i start my car and the rpm showed 600 rpm in P and 550 in D idrove my car around and the car drive smoothly with smooth gear changing .