EUROJulian

Hi there. I recently was encouraged to do ISC valve maintenance job on my SC400.
It was fairly simple job and advice was warranted by the condition of the valve I found after dissasembly, so I decided to share some. Please, those who are wrench challanged dissregard whole message, this is a geerhead only thread...

ISC is a fairly big device on our engine. Interesting it is not located on TB like usual, but in front of the intake plenum.
ISC is run by the stepper motor with like 120 possible positions or so.
What is also unusal, motor can be taken appart. I took the opportunity to do just that as I felt it may need some TLC after 12 years.

Rotor of the stepper sits on two miniature ball bearings, cleaning and lube of those bearings, together with shaft and screw mechanism of the valve is our objective here.
I would also recomand replacement of all small coolant hoses conected to the valve and farther alongsider of intake plenum into the both dirrections.
Valve gasket is paper and it need to be replaced as well.

Motor is bolted by three scrws to the valve body. Three more screws hold it together.
After dissassembly check if ball bearings spins freely, my wasn`t. With pick tool It is easy to pop protective rings on the bearings and give them good cleaning. I was told to pack those bearing with grease, but I do not think it is good idea since it will create more drag in such a small device. I lubed them with synthetic oil and put some techincal vaseline. Rings should pop in place easly.
Next "mushrom" shaft, there will be carbon there, clean it. Some cleaning and lube to the drive screw and we are ready for assembly.

Few last toughts. After removal from engine valve can be bench tested for operation by applying power and simultainously grounding specified terminals. Mushrom should move. Check manual for therminals numbers and specified instructions.

Lastly just in case, I think It would be beneficial to record the position of the mushroon in relation to the valve body before dissasembly and later assembly the valve in the same position.

Have fun...

Nomis

Good writeup. For those wondering ISC = Idle Speed Control. Julian, did you have any problems with idle before cleaning? Did the cleaning rectify the issue?

EUROJulian

No I didn`t have idle problems. Pure preventive maintenence.
I have fellows on the Lexus side getting me tips once a while. That was one of them. Addressing common problem areas....

SCV8

So the stepper motor was doing fine at overcoming the sticky bearings, but wouldn't have lasted forever in that condition, interesting. I've heard that the idle doo-dad isn't exactly free either.
I'll have to check that one out, thanks for the tip.

EUROJulian

I would not call my bearings sticky, gritty is the word in English which I think better describe the condition I found.

Senator

nice, I can see premature bearing failure, stuck throttle, (if possible not if it is,) and BOOM.

Thanks for the write up. It will be going with the rest of my Tech on the SC's.

It's always a plus when there is a Toyota Mechanic on board!

Josh