VY Commodore Series 2 Idle Issues

[mindedrobin]

My Series 2 VY Commodore has lately been having issues with its idle. This issue starting with a high idle about 1500 rpm about a month ago. Where then I cleaned the Throttle Body and replaced the IAC and Throttle Position Sensor, the only code on the car was an abnormal idle code. Then the car appeared to drive fine for a short time. Then the high idle returned, I then found and fixed 2 vacuum leaks using a smoke tester fixing leaking on the hoses from the EGR and the Charcoal canister to the intake. This did not solve the high idle and it then developed into a high and or low idle in the car, the old and new IAC we both tested and read 50 ohms across the a b and c d pins and no continuity between the pairs which is what the manual says is within the expected resistance.

Then the car developed into a only low idle where the IAC would go to 220 steps and cause the RPM of the engine to fall down to 300-400 rpm when not on the accelerator and at one point stalling the car while braking. But besides the 1 time it stalled the car would manage to idle at 400 rpm but this issue only seemed to appear when the weather was warm, on cold days the car would drive fine and warm days or afternoons the issue would appear. Now the car goes from starting perfectly fine and driving perfectly to then a high idle, then to stalling itself when trying to start.

Then when it would start the idle would be low then if you accelerated it would then stay at 1000 then if you accelerated again it would go to 1200. And though this all there have been no engine codes besides the abnormal idle after the car idled high. The intake air temperature sensor was the next thing I expected but it read the correct air temperatures. This issue only seems to happen when the car is in taking warm air. It has been tested for vacuums leaks when cold and at temperature having just been run. I have no idea what is causing this issue now.

 

[Lex]

My Series 2 VY Commodore has lately been having issues with its idle. This issue starting with a high idle about 1500 rpm about a month ago. Where then I cleaned the Throttle Body and replaced the IAC and Throttle Position Sensor, the only code on the car was an abnormal idle code. Then the car appeared to drive fine for a short time. Then the high idle returned, I then found and fixed 2 vacuum leaks using a smoke tester fixing leaking on the hoses from the EGR and the Charcoal canister to the intake. This did not solve the high idle and it then developed into a high and or low idle in the car, the old and new IAC we both tested and read 50 ohms across the a b and c d pins and no continuity between the pairs which is what the manual says is within the expected resistance.

Then the car developed into a only low idle where the IAC would go to 220 steps and cause the RPM of the engine to fall down to 300-400 rpm when not on the accelerator and at one point stalling the car while braking. But besides the 1 time it stalled the car would manage to idle at 400 rpm but this issue only seemed to appear when the weather was warm, on cold days the car would drive fine and warm days or afternoons the issue would appear. Now the car goes from starting perfectly fine and driving perfectly to then a high idle, then to stalling itself when trying to start.

Then when it would start the idle would be low then if you accelerated it would then stay at 1000 then if you accelerated again it would go to 1200. And though this all there have been no engine codes besides the abnormal idle after the car idled high. The intake air temperature sensor was the next thing I expected but it read the correct air temperatures. This issue only seems to happen when the car is in taking warm air. It has been tested for vacuums leaks when cold and at temperature having just been run. I have no idea what is causing this issue now.

You had the lim of recently?

Any modifications?

 

[mindedrobin]

No modifications car is stock.

 

[Lex]

the old and new IAC

Where did you buy the iac from?
There are 2 different iac, which one did you buy?
One is pointy shape the other is more domed shaped.
Vy has the domed shape.

You haven't answered the question about lim (lower intake manifold = lim) yet?

 

[mindedrobin]

No the lim has not been off the car. But I don't belive there is a leak there as the smoke test would have revealed that.
And the new iac was a goss domed one and looked exactly like the old iac.

 

[mindedrobin]

And I should add this issue only seams to appear when the air is warm. When it is cool or the car is moving at speed the issue does not appear. But on warm days or when stoped in traffic and then once it starts it will not go away.

 

[lout]

did you fit the little tps adaptor when you changed tps

 

[mindedrobin]

did you fit the little tps adaptor when you changed tps
View attachment 257541
View attachment 257542Yep, I ensured that that plastic remained and the readings of the throttle position sensor when driving is reading the throttle values correctly.

 

[Fu Manchu]

A valve issue?

 

[mindedrobin]

The low idle and stalling has now been fixed by putting another replacement IAC in as it turns out the 1st replacement IAC was faulty and was causing the issues.