MrWinkle Posted May 18, 2011 Share Posted May 18, 2011 Hello guys and gals, I have been having this issue with my 1990 lex ls400 for about three weeks now. I took off the throttle body, cleaned it, and the intake and i still have this problem. Do you think the throttle position sensor is the culprit? PLEASE WATCH THIS VIDEO BELOW. It will explain it a whole lot better than me. Thanks in advanced Quote Link to comment Share on other sites More sharing options...
steve2006 Posted May 18, 2011 Share Posted May 18, 2011 Check all your vacuum pipes and the IACV. From the video (good idea BTW) it looks like there is insufficient air flow at idle so the engine stalls,the valve is located on the front of the plenum chamber to the right of the coil. 2nd post on link may help http://us.lexusownersclub.com/forums/index.php?showtopic=42315 Quote Link to comment Share on other sites More sharing options...
curiousB Posted May 18, 2011 Share Posted May 18, 2011 Ditto dirty and/or sticky IACV and or vacuum leak on intake ducting after the MAF. I'd start by removing the IACV and scrub it down good with cleaner. Lubricate moving parts and make sure it isn't binding. Quote Link to comment Share on other sites More sharing options...
MrWinkle Posted May 19, 2011 Author Share Posted May 19, 2011 cleaned iacv problem got worse alot worse. so does anybody know how to rebuild one of these things? Quote Link to comment Share on other sites More sharing options...
steve2006 Posted May 19, 2011 Share Posted May 19, 2011 I don't think you can rebuild them replacement is the only option,another possible cause could be the the TPS.There is a switch in the unit which activates when the throttle is fully closed (idle position) the switch then sends a signal to the ECU to inform it the throttle is closed which should then result in the IACV opening to supply the idle air supply,if the switch is faulty it would cause idling problems. Quote Link to comment Share on other sites More sharing options...
MrWinkle Posted May 19, 2011 Author Share Posted May 19, 2011 I buying a used iacv okay new ones are about $700+? Quote Link to comment Share on other sites More sharing options...
curiousB Posted May 20, 2011 Share Posted May 20, 2011 This could get expensive if you just start throwing parts at it. The IACV is a pretty simple device. An electromagetically actuated valve. If you search the forum there is a test procedure for checking the coils. It just takes a simple ohm meter. You don't want any coils to be opens or shorts. The mechanical test is visual. If you can move the valve with your finger and it isn't binding it should be ok. If its sticking at all clean and lube. Repeat until it moves freely. Here is a cleaning tutorial: http://www.clublexus.com/forums/rx-first-generation/358579-diy-iacv-clean-picture-write-up.html Testing and bearing replacement.. http://www.planetsoarer.com/IAC/iac.htm Quote Link to comment Share on other sites More sharing options...
MrWinkle Posted May 27, 2011 Author Share Posted May 27, 2011 Okay, check the codes and now the plot of this story has taken another turn. I got code 13 - RPM signal no. 2 and code 52 - No. 1 knock sensor signal. Now the check engine light has been on since i bought the car, I had her timing belt and water pump changed but she ran fine up until now. So does this rule out the TPS and IACV and have the cam sensor and/or knock sensor signal been behind this the whole time? Quote Link to comment Share on other sites More sharing options...
MrWinkle Posted August 17, 2011 Author Share Posted August 17, 2011 Help!!! can anyone answer the question above? Quote Link to comment Share on other sites More sharing options...
92LS400...s/c? Posted August 27, 2011 Share Posted August 27, 2011 dang, that happened to my mom's car and my car when I changed the water pumps on ours, hers a 94 mine a 92. It turned out on her I forgot to plug the MAF sensor back in(I know, dumb) but it ran almost exactly the same and also I had put the passenger side rotor on backwards. So maybe you should check those but since you said it ran good for a while it might not be. My car the 92 what had caused the rpm signal 2 code was i guess some water got in the coil on the top, thats the rpm signal 2, the coil went bad so i replaced that fixed that code; then, the knock sensor was when i had reran the knock sensor i didn't hook it back under the coil which caused the serp belt to rub it and eventually cut the wire so i had to go to pick n pull and get a new after that the idle went back to normal on both cars and ran fine. So to recap check the MAF sensor, make sure the rotors on correct, check if knock sensor wire is cut and replace coil if needed Quote Link to comment Share on other sites More sharing options...
92LS400...s/c? Posted August 27, 2011 Share Posted August 27, 2011 oh, the way i tested the coil was just unplug it while the cars running. If it's good the idle should seriously mess up, if nothing happens it's probably bad. Plug it back in and unplug the other coil just to make sure, if that one good and the others bad the car will die Quote Link to comment Share on other sites More sharing options...
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