ISC Valve Diagnosis/Benchtest Question

[dasz33]

Hello all,

I have an 88 N/A Supra, 5 speed with a high idle (steady 1200 rpms or so).

Going through the diagnosis I came to the ISC Valve. I dont hear any clicking from the valve after shutting off the motor. So I pulled it out for a benchtest. All of the ohms are good at about 25 ohms. When I connect the battery to B1 and B2, and then ground S1-S4, the valve thumps/thumps, but does not seem to move.

My question is, how far is the valve supposed to open and close? Should the valve completly seal, and then how far should it open? Are we talking 0-4mm kinda distances or more like 0-10mm?

I suppose the next question would be, if mine is bad, are the Turbo and non Turbo valves the same? And does anyone have one for sale cheap?

Thanks all
Doug

 

[Piratetip]

Can start with this.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=106
May help may not.

The valve should move in increments depending on which connector you are grounding <S1 S2 S3 or S4

 

[dasz33]

Can start with this.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=106
May help may not.

Thats what I am already using. And it does not mention how far it opens or closes. But it does not seem to be moving at all, so Im guessing its bad.

 

[Piratetip]

The valve has 4 positions, so it should noticeably move. I do not know how far the total movement is though. Do you have it off the vehicle and are testing it?

Yeah sounds bad, you (could) try cleaning it to clear up any gunk and free up.

 

[jetjock]

Open it up further and look at the drive screw and holding plate. You should be able to see the shaft step. You can put a tie wrap with a long tail on it to amplify the movement. It has a lot more than 4 positions.

 

[Piratetip]

Good to know.

 

[dasz33]

ok thanks guys. I will try cleaning it out, since it does click, but it doesnt seem to move.

Anyone have one availble? Dealer wants $500 for a new one...and thats more money than I have in the car...

Thanks again
Doug

 

[jetjock]

Pull off the motor cover. Clean, check the bearings and drive screw, holding plate, lube it up, then reassemble and test. Eyeball the check valve in the manifold too.

I've never seen one that couldn't be repaired unless the windings were bad. You just have to go further inside it than many people do. That said I doubt it's the cause of your idle problem but I suppose it could be.

 

[phoenix6]

Idle adjustment screw, best thing Id ever found haha, along with fixing my ISC hose that was busted and dry rotted, and setting the timing back to 10* BTDC

 

[figgie]

The valve has 4 positions, so it should noticeably move. I do not know how far the total movement is though. Do you have it off the vehicle and are testing it?

Yeah sounds bad, you (could) try cleaning it to clear up any gunk and free up.

what?

the ISC valve has exactly 255 positions.