Low Idle BS

[Davo_vx]

Yeah mate already own advanced engine diagnostics useful tool at times, still haven't been able to pinpoint my problem this time around though. Currently running a few tanks of 98 and put in some ultraclean hoping for the best atm. Seems to be running abit better on the whole but hasn't fixed the issue completely. Nice engine.

 

[klrtim]

Also when I bought this one about a year ago the bloke said he'd had the aircon recently worked on don't know if aircon can cause idle issues?

My 1999 vt was doing the same thing I found the vacuum that is running the heater controls was not connected behind the dials. Whoever fitted the double din stereo left the vacuum unatached. also i found a vacuum leak at my supercharger boost control Solenoid, not the Booster bypass valve, this solenoid is behind Bank 1s head. All good now

 

[Fu Manchu]

"PROBLEM DESCRIPTION

Some owners may complain of the following symptoms:
With vehicle speed less than 3km/hr or vehicle stationary, the engine idle is too high; e.g. 1000RPM+, and engine may later stall or the idle may remain high.

This is caused by a build-up of engine by-pass gases and IACV solenoid shaft/bearing wear particles on the IACV solenoid shaft, which causes the IACV to stick at any point in its operating range.

This will result in either too high or too low IACV air entry to the throttle body and engine. When the IACV subsequently “unsticks” and returns to normal operation, the result may be a stall or higher than normal idle RPM. It is not possible to effectively clean the IACV to correct this condition."

Revised IACV design was the solution. Some Throttle Bodies would still be in circulation.
What if the solenoid shaft is simply worn as well and sticking? I'm not quoting the high idle stuff specifically. Just an idea that the solenoid might be a bit "how ya goin"

Vacuum leaks could be an issue too. Maybe block off some of the vacuum lines and see if idle improves. Brake Booster might be one. Interior HVAC vacuum.

Make sure the intake plenum is bolted down properly.
No tears in the throttle body gasket?

 

[Davo_vx]

Yeah mate checked or replaced everything you have mentioned there apart from HVAC vacuum.

 

[mirrabucca]

Hi.
Any progress?
I have had this on my VX Spack. Turned out to be a vacuum leak... (Yes, I know.)
I got to the stage of shifting into neutral before the car stopped at lights etc.
It was a vacuum leak from the TB gasket. I found it when the car was idling bad and noisy. I dropped the main belt off so I could hear the noise above the other whines a 331000 k engine makes! As I moved the TB up the hissing stopped.. Gotcha!
Maybe check the plenum chamber where the TB bolts on for square/flat (run a striaght-edge across it to be sure as you have replaced the TB already).

 

[Davo_vx]

Hi.
Any progress?
I have had this on my VX Spack. Turned out to be a vacuum leak... (Yes, I know.)
I got to the stage of shifting into neutral before the car stopped at lights etc.
It was a vacuum leak from the TB gasket. I found it when the car was idling bad and noisy. I dropped the main belt off so I could hear the noise above the other whines a 331000 k engine makes! As I moved the TB up the hissing stopped.. Gotcha!
Maybe check the plenum chamber where the TB bolts on for square/flat (run a striaght-edge across it to be sure as you have replaced the TB already).

I had been doing the same thing when pulling up to lights but now it's only dipping occasionally at a stop but just generally running rough as at idle I haven't tryed replacing the Tb gasket maybe I will and see what happens.

 

[Davo_vx]

Yeah no luck swapped it out for a new one same dramas. Cheers for the idea though.

 

[Davo_vx]

Something I am curious about is when I scanned this car when I first got it I got a torque of range fault code p1571 I believe. Which I thought related to the abs unit so I replaced the unit and cleared the code and it hasent returned. But I seen earlier today a post on here saying that a p1571 would indicate also the pcm needing to be reflashed... can anybody shed some light on this fault code?