iacv-idle problem low idle car dies

[grindin8o8]

Car-1993 sc400
Problem-

On a cold start up my car idles in park at around 1200-1500 rpm. sometimes it loops(goes up and down) from 1200-1500 rpm repeatedly. In gear it idles at a little above 1000 rpm.

When the car is warm my idle is very very low. just above the 0 rpm mark, basically no idle. and after about 3 minutes the car dies out because of the low idle. The car won't start up if I don't give it a gas or keep the throttle open I guess??? So no matter what I do if I don't keep my feet on the gas pedal the car will die.

Any one can help?? I've searched and found that it could be the iacv, tps, or a vacuum leak??

When I tried removing the whole assembly of the iacv I ran into a problem. One of the hose had coolant coming out of it when I tried removing the hose. What do I do to remove this hose?? if I take it out won't there be coolant spilling out everywhere?? do I have to drain the coolant first?? or is there another way?? help please?? I really want to clean out my iacv before I do anything else. also some of the whose were hard as a rock.

 

[lexdud]

I just recently had a very similar issue with my '93 SC400 with 52K miles. The car would start/run ONLY if you gave it some gas. If you released the gas it would die. I took the car to the Lexus dealer and was told that it was a bad IACV and possibly a bad ECU ($695 + $1,500). I bought some used parts off the Net and replaced the IACV ... still no idle. I then replaced the ECU and now it works wonderfully ... all for about $300.

As for the IACV ... do not remove the whole assembly (including the plate. Just (carefully) remove the three screws that holds the black plastic stepper motor on and then you can clean out the IACV. Don't forget to check the bearings. If they are not moving smoothly I would either replace them or buy a used IACV. The problem I am running into is that I cannot find the larger NSK 6902v bearing anywhere.

 

[zen]

try 61902v or z..

my bearing supplier had it under that number(he had not heard of 6902)

 

[grindin8o8]

I just recently had a very similar issue with my '93 SC400 with 52K miles. The car would start/run ONLY if you gave it some gas. If you released the gas it would die. I took the car to the Lexus dealer and was told that it was a bad IACV and possibly a bad ECU ($695 + $1,500). I bought some used parts off the Net and replaced the IACV ... still no idle. I then replaced the ECU and now it works wonderfully ... all for about $300.

As for the IACV ... do not remove the whole assembly (including the plate. Just (carefully) remove the three screws that holds the black plastic stepper motor on and then you can clean out the IACV. Don't forget to check the bearings. If they are not moving smoothly I would either replace them or buy a used IACV. The problem I am running into is that I cannot find the larger NSK 6902v bearing anywhere.

i cleaned out the iacv but still have the looping when in park and neutral. the rpm needles bounces up and down from about 1300-2000 rpm continuously with the engine responding to it. and what i notice is that in drive, the car accelerates on it's own till about 30 mph. but i'm also experiencing starting problems with my car now.

 

[lexdud]

i cleaned out the iacv but still have the looping when in park and neutral. the rpm needles bounces up and down from about 1300-2000 rpm continuously with the engine responding to it. and what i notice is that in drive, the car accelerates on it's own till about 30 mph. but i'm also experiencing starting problems with my car now.

My best guess (for what that's worth) is to consider replacing your ECU with a known good working unit. If that does not work then all bets are off.

Sorry ...