ISC ? (searched)

[forcefedsupra]

I have an idling problem and I think it is the ISC. I checked it per the TSRM and it says The terminals should measure 30 ohms. Mine all measure 21-22 ohms. I also can't manually move the valve in or out. Is this something to be concerned with or am I barking up the wrong tree?

 

[dbsupra90]

eh, i dont think that would be a concern, that isnt too far off.

that little ufo filter often gets dirty or the stepper motor gets gooped up. id take it apart and clean it all real good. also be sure you put it all back together in the right order.

what is the idle problem anyway?

 

[figgie]

the ISC, I think in all my years of owning a supra I can count one hand the number of times one has actually failed.

The ISC is not your problem.

 

[forcefedsupra]

My idle is very rough. The car dies and barely runs without my foot on the gas. It runs like a bat out of hell when I am driving but I have to give it gas at stoplights. I will check my timing asap. What are some other options?

 

[figgie]

check that the TPS is adjusted correctly. That will more than likely be your culprit.

 

[supra90turbo]

Concerning the ISC, make sure that it returns to "start" positioning when you shut the car off, meaning when you turn the key to the off position, the ISC should go *ticka ticka ticka ticka tsssst*

Check TPS adjustment as Figgie stated, also check your plugs and wires. Check timing, check for any leaks in the induction system, be it boost or on the accordian hose.

also: what are your mods?

 

[JesseH]

the ISC, I think in all my years of owning a supra I can count one hand the number of times one has actually failed.

The ISC is not your problem.

Ive had my ISC and my TPS go bad:aigo:

A lot of times when people think their ISC is going bad its really just because of too much carbon build up over time so you might want to try cleaning it first, and check the calibration of your TPS while your at it.

 

[TurboStreetCar]

mine surges sometimes when its cold, i beleive it to be the ISC because it only does it when cold. and after it warms up and the ISC like closes or almost closes all the way then its good.

sound like a symptom of a bad or gunked up ISC?

 

[JesseH]

mine surges sometimes when its cold, i beleive it to be the ISC because it only does it when cold. and after it warms up and the ISC like closes or almost closes all the way then its good.

sound like a symptom of a bad or gunked up ISC?

possibly, it could be a few different things. If your curious you can always take if off and clean it out, its not hard and doesn't take long. You can either remove the 3 philips screws (sometimes tend to be stuck) or you can take off the two hex bolts and the small coolant line the passes through it. Then just use carb cleaner and a Q-tip.

 

[jdub]

There's also a check valve under the ISC in the intake manifold flange...looks like a little mag wheel. If that is carbon fouled/blocked up, it will cause problems idling.

 

[forcefedsupra]

I already took it off and it was pretty clean but I went ahead and cleaned it anyway. The check valve is pretty gummed up. I will clean it better and adjust the TPS (which I did fairly recently). My plugs and wires are only about a year old but I will check them. Does it mean anything that I can't push or pull the little valve on the ISC? The only mods I have that are related are MAFT, SAFC, AVCR and I think that's it. I have had those a while and no problems until recently.

 

[jdub]

If you want to test the check valve, just install the ISC without the check valve. You can't leave it that way...it's purpose is to prevent back flow to the ISC under boost. The check valve does allow air into the intake manifold at idle...it's always open when the manifold is under vacuum. So, if you remove it, re-install the ISC, and the car idles correctly, there's your problem. Get a new one from Toyota...they don't clean up well.

You can clean the ISC as previously posted...that may help. The ISC is a step motor, it won't move unless the ECU provides the electrical signal. It should step open when the motor is shut down (key off) like supra90 said in post #6. You can confirm that by listening to it or visual inspection by removing it.

BTW - What plugs and wires are you using?

 

[supra90turbo]

/\ hopefully not 3923's and Moroso's

 

[jdub]

/\ hopefully not 3923's and Moroso's

Or 3923's and MSD wires either

 

[TurboStreetCar]

slightly offtopic of operation, but since i have the maft, i would like to run blow threw but i would have to have the inlet of the ISC on the boost side of the turbo then. that would run ok?

 

[forcefedsupra]

I have autolite coppers and Toyota wires.

 

[jdub]

I have autolite coppers and Toyota wires.

Be aware the Autolite 3923 plugs are about 1/8" shorter than stock. On my MSD wires, it caused a light misfire due to the poor connection between the plug and wires.

 

[bluemk3]

the ISC, I think in all my years of owning a supra I can count one hand the number of times one has actually failed.

The ISC is not your problem.

i have one fail due to the gasket wearign and lettin gwatter into the bearings and locking them up making for an extremely eratice idle a pulseing from 500 to 3000 rpms every second or two mine did fail so i wouldt rule it out but to who stared the post i did tear mine apart and cleaned it and spun the bearings loose ( they werent smooth but they spun) that works for a whiel befor i gave in and bought a new one due to my concients bothering me about it

 

[forcefedsupra]

The check valve has a tear in it, so I will replace it. I installed the ISC without it and the car idled fine. The only problem is, when I turn the car off, no clicky clicky form the ISC. I cleaned to contacts but it didn't help. Any suggestions?

 

[supraman7mgte]

tickka tickka make the demon work. yours is obviously out,go to a junkyard and get a replacement and viola! tickka god's happy.