Idle / tune issues on VR V8 304

[Stanpro]

I've had a problem for a while on my VR Clubsport manual. Idles high at around 1200 - 1300 rpm. I've tried resetting the idle, new IAC valve, new TPS sensor and a few other things. Also If I hold the rpm at maybe 2000 rpm it will sound fine but after around 5 seconds it sounds like it starts to run lean and keeps getting worse.
Could it be oxygen sensor?

Cheers.

 

[Deuce]

Check the vacuum hose to the map sensor.

Unlikely to be O2 sensor issue, as they don't do a lot on these older motors (fuel trim at cruise is about it)

 

[Forcedvp]

If not what Deuce said then look at intake manifold gaskets. And check intake manifold bolts to ensure they are torqued correctly

 

[vr304]

Sounds like a vacuum leak to me, check all your vaccum hoses and the air intake for any splits loose clamps etc

 

[BlackVXGTS]

+1 for vacuum leak. Holden VS Workshop manual says that a vacuum leak causes a high engine idle.

 

[Stanpro]

Thanks for all the replies. Not a vacuum leak as I've been doing some playing around with the ALDL cable I have. Using this I can shut the IAC valve and stall the engine or it idles down to around 550 rpm which it should do with the valve closed as per the manual. I then figured out using efi live to request idle speed to 750 rpm and it idles perfectly at 750. As soon as I disconnect the cable the revs increase again to over 1300.

Also I noticed closed loop idle is on when I set it to 750 but when I disconnect the ALDL cable it goes into open loop idle. What conditions need to be met to go into closed loop idle?

I have a vortech supercharger on the car what I put on years ago. It used to idle fine when I first put it on. I did the head gaskets years ago and after that I think it started having the idle issues. I don't think I got any of the vacuum line plumbing wrong as the car drives ok.

If I do the idle adjustment procedure it idles ok when first starting but when I do the rev over 2000 bit it doesn't return to normal idle.

Any ideas what might be going on?

Thanks.

 

[Forcedvp]

That's strange with how it's acting with the ALDL cable dis/connected. Sounds like a tune issue. Like timing settings in the tune.
What's your temp readings in the software?

 

[Stanpro]

Intake and coolant temps all good according to the readouts on the laptop. I can see it's requesting 750 RPM idle but something isn't letting it go into closed loop idle. The map sensor reading seems a bit off but I don't know if that's because it's the one that came with the supercharger kit many years ago and that's the way it is set up. With engine off it's reading 50kpa. Atmospheric pressure (no vacuum) I thought should be 100 kpa. I'm guessing it's a 2bar MAP sensor (no part numbers on it, just a CAPA sticker) and maybe whoever did the flashed tune that came with the kit set up the tune like that.

New problems now though. Ignition module just crapped itself so have to sort that out before sorting this out...

Cheers

 

[gtrboyy]

IAC & TPS values within factory values?

Would expect map sensor to affect fuel but if it's supercharged anything is possible & if it's old maybe change it just in case.

I'd pull easy stuff off give it a clean out & going over then put back together hopefully fluje it.

Had tuned vy sv8 once in a blue moon after it copped a hiding would idle 1500rpm

 

[Deuce]

Intake and coolant temps all good according to the readouts on the laptop. I can see it's requesting 750 RPM idle but something isn't letting it go into closed loop idle. The map sensor reading seems a bit off but I don't know if that's because it's the one that came with the supercharger kit many years ago and that's the way it is set up. With engine off it's reading 50kpa. Atmospheric pressure (no vacuum) I thought should be 100 kpa. I'm guessing it's a 2bar MAP sensor (no part numbers on it, just a CAPA sticker) and maybe whoever did the flashed tune that came with the kit set up the tune like that.

New problems now though. Ignition module just crapped itself so have to sort that out before sorting this out...

Cheers

50kpa is about right.
20-30 is decel
40-60 is possible idle range
70-100 is accel
over 100 and you are into boost.