ISC valve ? Block off/reroute?

[SevenMKIII]

Finishing up my build and I was wondering about the ISC valve. I noticed someone on here simply blocked it off, are there any negative effects to this? I'm using the VPC so the maf is gone and I'm just using a 3" aluminum pipe off the turbo, and there aren't any ports for the ISC hose. Thanks in advance! I've been working on this wayyy too long.

-Chris

 

[jetjock]

If you defeat the ISC you'll loose all the benefits of automatic idle speed control. You'll also have to provide another bypass path for idle air. If you have an older throttle body with an idle passage you can use that. If not you can crack the throttle itself. Where people get into trouble doing that is they don't reset the TPS. That's assuming there's even enough adjustment left to do it. The procedure in the TSRM becomes invalid of course. If it were me I'd reroute the ISC or use an external one.

 

[F_T_F]

im just guessing here but i dont think you can block it off. whenever i put my finger over the line running to the accordian hose it just dies. i believe what the ISC does is leans the fuel mixture up at idle. someone please correct me if im wrong though

 

[jetjock]

It doesn't lean the mixture. All it does is allow the engine to breathe at idle. In most EFI systems the throttle plate is fully closed there. Obviously the engine still needs to get air if the throttle plate is closed or it can't run. The ISC bypass path supplies that air. It's a shortcut around the TB. Plugging it chokes the engine. Think of it as putting a trash bag over your air filter.

 

[dbsupra90]

yep jj is right.

if you dont understand how it works you prob need to put it on. easiest would be making a remote mount one and extend the stock wiring.

 

[F_T_F]

oh ok well them what should the afr be at idle mine is in the neighborhood of 18-20.

 

[jetjock]

At hot idle the engine should be in closed loop with an a/f of stoich. Yours is lean, bordering on the lean misfire region. Something is wrong.

 

[F_T_F]

At hot idle the engine should be in closed loop with an a/f of stoich. Yours is lean, bordering on the lean misfire region. Something is wrong.

car runs fine i start driving and the afrs fine it stalls out sometimes at stoplights but hasnt done that in a while. im runnin a map ecu but car ran fine whem it was first put im a year ago.

 

[SevenMKIII]

Making a remote mount one...Any leads on this? Can I just install the stock one in the stock location without a hose on it if it is just bringing fresh air into the motor? Tiny filter over it? Thanks for the replies

-Chris

 

[dbsupra90]

yep you can on the vpc

 

[cnewingham]

I'm not using one on my car and I am alos running the vpc. I however am using a different tb and have it cracked open a little. It is a pita when it is cold but once warmed up I have no more issues and retain my idle around 800rpms. Some bump the idle up over 1000 but I didnt.

 

[SevenMKIII]

Awesome, thanks a ton I think I've got a good idea of how this should work then... Maybe this will finally keep my motor running after a 5 month rebuild!!

-Chris

 

[IJ.]

Most ICS are pwm based solenoids the Toyota one is a 6 wire stepper so is very accurate when working correctly, I've used both types on 7M's and would prefer the Stepper by far even if it means dropping some extra cash getting it working correctly.

 

[jetjock]

Agreed. Steppers are the best way to do this type of thing. It's why the stock ECU can hold idle within 20 rpm. By keeping the valve he'll retain all of the ISC system's benefits ie; ramped warm up, idle up for headlight, AC, defogger, etc. Imho it beats cracking the throttle plate but to each his own.

 

[cnewingham]

I do have to agree that if I was able to keep the ISC I would have.

 

[alloyguitar]

I'm curious. I have just purchased a maf-translator from a fellow forum member and am trying to figure out how I can eliminate the isc, or possibly relocate it, as I will be fabricating a ffim in the not-too-distant future...

...could anybody shed some light on this for me?

-Devon Goodspeed

 

[Ric]

I removed it off my 1JZGTE and used the factory idle adjustment screw in the throttle body (longer one). Cleaned up the engine bay alot. I get 600rpm cold idle, 1000rpm operating temp. Perfect.

 

[Evilempire1.3JZ-GTE]

I have even heard of someone going as far as to drill a small hole in the TB plate to alow air to bypass when its closed off completely.

 

[Ric]

^ He's a mk3 owner that lives in Orlando that posts on SF.

 

[dbsupra90]

w/ the maf-t it really needs the isc since it isnt map based. you need to tap the isc anywhere between the maf sensor and the throttle body.

for the ffim it would be easiest just to make a remote mount unit.