Idle Speed Control

[Lextreme II]

Anyone with SC400 having idle problem? I have in my LS400 recently and got a 95 SC400 ISC from JamesN. I found out the SC400 (at least 95) is slightly different from the LS400. The LS400 is a two parts. ISC and the housing. A very good article from Planetsoarer on repairing the ISC. However, in the SC400 the isc is NOT repairable. The SC400 ISC is one unit and unable to seperate the housing from the ISC. This is just a FYI. Perhaps i can take some pics and compare them for you guys. My suggestion would be if you see a ISC from a LS400. Buy it and keep it. They are hot part to get.

 

[Lextreme II]

I called around and found the bearings stated by Peter Scott. The bearing part number 608V is about $3.59 USD and the 6902V (61902V is more universal and its the same as the 6902V) is only $4.10 USD. I will post a video on this tutorial soon. Pictures courtesy of www.planetsoarer.com

 

[fencera]

First, this is some great information. Thanks a lot.

Second, I have looked around online... where did you manage to find those bearings? I have been unable to locate them.

Thanks!

 

[do92sc400]

any luck finding these bearings at the local autozone?

 

[GSMnow]

Thanks for this info. I will certainly be needing it soon. My Lexus swap into my Celica has no high idle at all. Once warm it runs great, but you need to keep your foot on it for 5 minutes until the engine warms up. I suspect the ISC is frozen. The motor is a 1993 LS400 1UZ.

 

[do92sc400]

Please help!!!

The problem I am having is that my 92 sc400 idles high at warm up, about 1800rpm, then when at proper temperature, the car idles up and own from almost 2000rpm then it drops down to 600 or so doing over and over every second. I took apart the idle speed control and checked the bearings. The top one was frozen bu then it broke loose and now spins freely. Put the isc back int the car and nothing changed. When I put it in gear, the revs stop jumping and the idle holds at 1000rpm. No check engine light has gone on so now I am really confused.

 

[GSMnow]

I am guessing that you have a vacuum leak between the air flow meter and the cylinders. That causes mixture errors that change alot with air flow rate into the engine. It goes rich and starts to stumble, then leans out and revs up again. My programmable MAP ECU based ECU would hunt like that when I had a bad slope in the fuel curve near idle, even with no idle air speed control working at all. And turning the idle air control on actually made it worse as it would try to adjust for the improper rpm and it would overshoot even more. With the AFM, an air leak after the flow meter can cause a very similar situation. The amount of air leaking is enough to lean it quite a bit at 600 rpm, and as the O2 sensor feedback richens it up, the revs climb, but then the air leak is no longer enough to keep the mixture, and it goes rich and stumbles down. Then the whole cycle repeats. To find it, try spraying carb cleaner around any vacuum hoses, intake pipes, and gaskets in the intake air path. The cleaner will stop the lean condition and stabalize the idle for a few seconds.