ISC Valve replacement.

[figgie]

87

if the car is idling high you can take the hose off the ISC and plug it. If it idles down, then you found your problem.

 

[jetjock]

figgie, good job. I'll take your word for it and stand corrected. Unipolar huh? In my defense all I can say is I have more experience with DC servo loops than steppers. You're right, it steps back 125 to full open but has twice that range. I was pulling much of that from memory so that'll teach me And I agree, I don't see any reason a stand alone wouldn't run the ISC valve as long as it's setup right.

 

[87CandyBlueT]

Which hose do i take off to test this and what problem is that i found?

What are the hoses that run to the ISC, what does bottom hose run to and what if it maybe loose?

 

[jetjock]

Which hose do i take off to test this and what problem is that i found? What are the hoses that run to the ISC, what does bottom hose run to and what if it maybe loose?

I'm about ready to give up on you. Read mine and the other's previous posts. All the information you need is there, clearly spelled out. What don't you understand? If the engine is idling high the likely cause is too much air being bypassed around the throttle body, either through the ISC valve or a leak.

 

[figgie]

figgie, good job. I'll take your word for it and stand corrected. Unipolar huh? In my defense all I can say is I more experience with DC servo loops than steppers. You're right, it steps back 125 to full open but has twice that range. I was pulling much of that from memory so that'll teach me And I agree, I don't see any reason a stand alone wouldn't run the ISC valve as long as it's setup right.

Jetlock

no problems

unipolar stepper motor is a stepper motor that only lets current go ONE WAY per leg. That is why the stock 7m ISC has 6 legs. two positive (b1 and B2) and 4 to ground (s1, s2 ,s3, s4). Current goes only one way (From B1 to S1, B2 to S2 et al). In a bipolar stepper motor current goes both ways (S1 to s3 to open the valve, S3 to S1 to close the valve). A unipolar motor CAN be used as a bipolar motor hence why it does work on a standalone as long as the standalone can control a four pin stepper motor. hope this has been educational for all

 

[jetjock]

Thanks figgie. I'm somewhat familar with unipolars and had I taken a moment to pull out the manual I might have saved myself. As I said, that'll teach me. I also agree with you that the ISC valves seldom go bad. I think lots of them are changed for no reason.

Lol, at least you didn't write jetcock....I get tried of seeing that mistake

 

[87CandyBlueT]

Thanks everyone. The big hard pre-bent hose was leaking, trip to toyota parts division fixed that. Now I've re-adjusted my idling and stop screw and the car is doing much better.