idle surging up and down when warm

hemi34 · 09-29-2010, 03:24 PM

After searching the forum for an answer to my problem I could not find one, I have this problem when my 90 non turbo supra warms up it jumps from 800 rpm to 1500 rpm continuously, I replaced the tps and adjusted it, but it did not fix it, I took the IAC valve apart and cleaned it but that did not fix it either. I took the IAC valve back off and then took the stepper motor apart, I found the lower bearing was frozen solid, moisture had gotten in there and stuck the bearing, I sprayed the bearing with rust disoverer and then carefullly turned the rotor back and forth, I kept doing it until finally it would spin freely. It should be free enough that when you bolt the valve back on you can push the valve in and out, it fixed my idle problem and helped the cold start idle also. I hope this will help someone else.
David

here is a link to the valve picture you will see the rotor in the top half.
http://www.cygnusx1.net/Supra/Librar...spx?S=FI&P=106

09-29-2010, 03:24 PM	#1
hemi34 Stock Join Date: Sep 2010 Location: texas Posts: 2	idle surging up and down when warm After searching the forum for an answer to my problem I could not find one, I have this problem when my 90 non turbo supra warms up it jumps from 800 rpm to 1500 rpm continuously, I replaced the tps and adjusted it, but it did not fix it, I took the IAC valve apart and cleaned it but that did not fix it either. I took the IAC valve back off and then took the stepper motor apart, I found the lower bearing was frozen solid, moisture had gotten in there and stuck the bearing, I sprayed the bearing with rust disoverer and then carefullly turned the rotor back and forth, I kept doing it until finally it would spin freely. It should be free enough that when you bolt the valve back on you can push the valve in and out, it fixed my idle problem and helped the cold start idle also. I hope this will help someone else. David here is a link to the valve picture you will see the rotor in the top half. http://www.cygnusx1.net/Supra/Librar...spx?S=FI&P=106 Last edited by hemi34; 09-29-2010 at 05:55 PM.