1G S90 throttle body High idle. Help!!

[Anthony Boni]

I can’t figure this out!! It’s driving me crazy. My RPM stays around 1500 only after a WOT pull. If I drive around normally, it doesn’t act up. Only after going full throttle the RPM stays high. I boost leak tested, set the TPS correctly, I’m simulating idle switch using TPS position. ISC motor and FIAV deleted. The throttle cable is not holding the throttle body open. The idle stop screw has no tension on the valve to hold it open. Once I do a WOT pull, I’ll pop the hood and push down on the throttle body valve to make sure it’s fully closed. I don’t know what else to look for.

S90 throttle body by the way!

 

[AWD-Tony]

If you have to manually get the throttle to close, it has to be the spring or something internal that’s causing it to stick.

 

[Anthony Boni]

If you have to manually get the throttle to close, it has to be the spring or something internal that’s causing it to stick.

No I make sure it’s fully closed and it is. Pushing down on the throttle body does nothing.

 

[AWD-Tony]

No I make sure it’s fully closed and it is. Pushing down on the throttle body does nothing.

Oh. Sorry I thought you had to manually close it after wot.

 

[AWD-Tony]

So after wot, the rpm at idle stays at 1500. When does it go back to normal? After normal driving or next start or cold start?

 

[motomattx]

Start pinching off vacuum lines when its acting up and see if it changes. What are you tuning it with?

 

[Anthony Boni]

Just drove and didn’t even go to WOT. Started idle surging and stayed around 1200 RPM. I’m tuning with ECMLink V3

 

[Vegas Smith]

Post a log of the activity. Most likely a vacuum leak.

 

[Anthony Boni]

I’ll post a log in a few minutes. I’ve ordered a FIAV block off plate to eliminate the FIAV and ISC as a possibility. I use neither one.

 

[Anthony Boni]

So after wot, the rpm at idle stays at 1500. When does it go back to normal? After normal driving or next start or cold start?

Next cold start it is normal until I drive it, then it idles high again.

 

[Anthony Boni]

I will be as descriptive as possible here.

Throttle body is closed, RPM surges around 1100-1500 after driving around a bit. Once the car cools down, cold start it and it’s fine. Drive it, same issue.

This is my understanding of what’s happening, correct me if I’m wrong. Being this car is on speed density, I know air has to be getting in somewhere AFTER the throttle body. The ECU sees 0% throttle position, TPS position is .63v, idle switch is active. So the computer knows the car is at idle. But it’s revving higher because of excess air entering. Once it revs higher due to the excess air, the ECU cuts fuel to attempt to maintain target idle RPM. Right?

The FIAV and ISC are still installed on my throttle body, the coolant lines are deleted, the ISC is not plugged in. I’m assuming air is entering in that area, however I can’t find anything on boost leak tests. So I ordered the FIAV block off plate to completely eliminate that section of the throttle body. I re checked base ignition timing again, and it was off. Somehow. I then went into the timing tables in link and lowered timing in idle areas as a last ditch effort to lower my idle. Locked in open loop, car acts the same.

 

[Anthony Boni]

Post a log of the activity. Most likely a vacuum leak.

Here is a log of the activity. You can see how high the idle is. I've lowered the FC offset to 0 (It was so high because my car would bog when I first rebuilt the engine it would bog down on coastdown.)

 

[Anthony Boni]

The FIAV does not have a block off plate installed. I thought it did. I believe there is air bypassing the throttle plate through the FIAV. Hence why during the boost leak test, I see nothing leaking.

 

[Vegas Smith]

The FIAV does not have a block off plate installed. I thought it did. I believe there is air bypassing the throttle plate through the FIAV. Hence why during the boost leak test, I see nothing leaking.

Yep, that's exactly what's happening.