ONLY Idles with ISC Valve Unplugged

[bowsercake]

With the ISC valve plugged in the car will startup but immediately die, it will not idle. If I unplug the ISC it will idle around 650 but after 10 seconds it will go down to 500 and will try to stall but it will still run for a min or two before stalling completely.

I have changed the valve and both seem to work, the resistance is fine per TSRM and they both click when turned off. However, I also have the Air Intake Temperature Sensor Code 24. Timing is a little off but close, its hard to adjust without a clean idle.

I have checked my vacuum hoses but, could a vacuum leak be my problem?

 

[MDCmotorsports]

Try another ISC

 

[GrimJack]

Have you cleaned the part in your intake manifold? They are often clogged up with gunk...

 

[jetjock]

^ Exactly. If the ISCV is indeed stepping full open upon shutdown (it's clicking doesn't necessarily mean that) and it's unplugged before the engine is restarted rpm should go to around 1400. If it doesn't the idle bypass path is either restricted in some other way or the problem doesn't lie within the ISC system.

 

[bowsercake]

This engine was recently rebuilt and has not been driven yet because of this issue. I did clean out all of the intake manifold and I cleaned out the ISC and the ISC pipes.

I set timing to 20-15 fluctuating with Te1 and E1 jumped. This raised my idle from 500 to 750. I checked the Cam Gears and the Crank and both were set to TDC properly. Using a vacuum gauge I get -15 at the back of the manifold at 750 and -10 or less at 500.

I can get the car to start with the ISC plugged in if I give it gas but it dies when I let off (the ISC activates). It will only idle with the ISC unplugged as before.

----------------
So, I sprayed carb cleaner on the intake manifold top-to-bottom gasket and the engine rev'd. So, the manifold is leaking. Would this alone cause my symptoms? The gasket is new so I'll try tightening it down once the engine cools.

 

[jetjock]

Sure, if the leak was large enough. The vacuum readings point to a pirate air leak too. Start with the manifold and go from there. Too bad you don't have a smoke machine. They make that kind of leak detecting work and a whole lot more effortless. You'd have to pry mine from my cold dead fingers.

 

[IwantMKIII]

This engine was recently rebuilt and has not been driven yet because of this issue. I did clean out all of the intake manifold and I cleaned out the ISC and the ISC pipes.

I set timing to 20-15 fluctuating with Te1 and E1 jumped. This raised my idle from 500 to 750. I checked the Cam Gears and the Crank and both were set to TDC properly. Using a vacuum gauge I get -15 at the back of the manifold at 750 and -10 or less at 500.

I can get the car to start with the ISC plugged in if I give it gas but it dies when I let off (the ISC activates). It will only idle with the ISC unplugged as before.

----------------
So, I sprayed carb cleaner on the intake manifold top-to-bottom gasket and the engine rev'd. So, the manifold is leaking. Would this alone cause my symptoms? The gasket is new so I'll try tightening it down once the engine cools.

Vacuum should be around -20 to -25 range.

 

[GrimJack]

Too bad you don't have a smoke machine. They make that kind of leak detecting work and a whole lot more effortless. You'd have to pry mine from my cold dead fingers.

Agreed. Love mine too... they can be picked up damn cheap these days anyway, and they are awesome for Halloween. You should all just go buy one.

 

[3p141592654]

Like this one?

http://www.walmart.com/catalog/product.do?product_id=3059936

 

[suprasnd]

After putting in my JDM engine I had idling problem after 1st start up. I was told that the computer had to relearn idle. After a few starts the symptoms started disappearing. I've noticed that if I disconnect battery for a few days I have the same problem. Just my 2cents.

Keith

 

[bowsercake]

I've pulled the EFI Fuse and disconnected the battery several times but no luck on it figuring things out. When I unplug the AFM it does not run any better or any worse so I do not think that the AFM is my problem. I had a small leak in the intake manifold but I tightened it up and it went away.

I pull full vacuum at 700+ rpm. Still, it only runs with the ISC unplugged...

 

[cuel]

"Air Intake Temperature Sensor Code 24." http://cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=96

If you know you have this code, you might want to test and replace as necessary.