Tuning 4AGE ITB's for Idle

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Joined: Tue Jan 17, 2023 2:18 pm

Tuning 4AGE ITB's for Idle

Postby hobochangba » Wed Jan 25, 2023 12:52 pm

Good Morning all,

I'm currently installing a 4AGE blacktop in a KE70 and have reached the point where i'm setting the idle up. Generally the car seems to respond to all sensor inputs, however the ISCV is having trouble restricting the intake air to a desirable idle point.

I've syncronised the throttle plates, blocked off unnecessary vacuum ports, checked thoroughly for idle leaks, I've basically isolated the system so that only the ISCV, Fuel Regulator and Throttle plates are the source of air. I've also double and triple checked everything, applied small amounts of silicone sealant to any manifold surfaces etc.

However, the car still idles at 1400 RPM (target is 800-900 depending on temp). If i cover my hands over an intake, it drops by 200 rpm or so, if i cover over two it drops a little more. When i blank off the intake port going to the ISCV, it drops to a more reasonable 700-800.

I want to run the ISCV, but it doesnt seem to want to close the idle controller when to actually match the target when setting the ISCV in an aggressive manner in the PID settings.

Any suggestions? Im new to tuning, fairly savvy with computers, and mechanically capable to put a car together (that doesnt work)?

Whats the usual diagnostic process for Idle tuning, ITB tuning, or leak finding?

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Joined: Mon Nov 14, 2022 3:20 am

Re: Tuning 4AGE ITB's for Idle

Postby kranyx » Thu Jan 26, 2023 4:05 am

have you tried capping off the idle valve to see if that's even supplying the air?

if so try cleaing out the inside of the idle valve with brake cleaner, it might be all gummed up

if you unplug the valve what happens?

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Joined: Tue Jan 17, 2023 2:18 pm

Re: Tuning 4AGE ITB's for Idle

Postby hobochangba » Thu Jan 26, 2023 3:15 pm

Yeah, I've capped the intake port before it reaches the ISCV and it idles at a much smoother 800-900.

Obviously this provides no idle control. If put my thumb over the hose, it drops down to the same amount.

I've taken the Idle controller out, Pulled it apart and cleaned the Valve side with some degreaser, loaded it up and kept spraying through it till there was no soot, and then ran some WD40 and rotated the solenoid knob a few times to ensure nice smooth movement. I tested it on the bench and had it full open and closed, at full close it still leaked air, but it was pretty restrictive.

My current hypothesis is: It seems to be possible that the ISCV is trying it heart out to keep it closed, but even at a minimum setting its still letting enough air.

As i've rebuilt these throttles, I was informed that there is a special coating applied to butterfly valves to reduce the amount of air drawn in by it. Which was likely washed away.


Ill update the thread if it makes a big impact.

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Joined: Tue Jan 31, 2023 11:01 am

Re: Tuning 4AGE ITB's for Idle

Postby Rwalton » Tue Jan 31, 2023 11:16 am

I've had the same issue on my 20v. I tried cleaning the valve out with not much change. I have another ISCV and it was not much different. I put a vacuum cap on the inlet to the ISCV with a 1/8" hole drilled in the middle. This got my idle to be around 1k rpm. It does not idle up as much as I'd like on cold start even though the PID shows 40% open. 40% is as high as I've ever seen it go.

Let us know if that coating helps.

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Location: Paris

Re: Tuning 4AGE ITB's for Idle

Postby ManuFromParis » Fri Feb 17, 2023 11:30 pm

I have a totally different setup (911 air-cooled Flat-6 3.2 with ITB) and in the beginning I had the same problem, until :
- I switched from closed loop to open loop
- I got the main parameters ok (BAC type: Complementary, frequency, output max)
- Then, for each cooling temp I adjusted the standard valve position (size of aperture) and it worked fine.
- I also reduced the ignition advance.
- Eventually I adjusted AFR in the 0-1500 area with very low TPS

But the last 3 steps work together, so it's an iterative tuning process.

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