vs 5.0l idle issue

[CommodoreVS]

Hey all I I bought a vs 5.0 ute not so long ago, I noticed especially when the motor is cold it nearly stalls when I come to a stop at lights etc..I have replaced the IAC,and spark plugs just wondering if it's the automatic choke? Or is it something more complex?

[BlackVXGTS]

Auto or manual ?

[2CYCO]

The ecu should control the idle via the iac.
Check for manifold leaks etc...
does the idle speed hunt prior to stalling?

[CommodoreVS]

It's a manual, it hasn't stalled yet. But at night lights dim out for a slit second until it idles back to normal. So it's running 750 idle then drops under 500 then upto 1000rpm then to normal 750 rpm.

[VR38]

maybe the alternator, when the charge is low the ecu plays up.
Check your voltage at idle.

[CommodoreVS]

What's I have recently changed to c if this fixes the problem, new alternator, battery , plugs, oil and filter, radiator flushed and new coolant, gearbox fluid, fuel filter, cold air induction, it also has a 3 " exhaust cat back with pacemakers so yer it's fairly loud too

[slammedvz]

Whats it like starting? Mine did the same and would sometimes stall, my injectors were shagged causing it to fuel up.

[VrWagz1]

Was goin to suggest the same. Injectors could be shagged. Have them cleaned and rebuilt maybe. Has the ecu logged any codes, it maybe that the ecu temp sensor if it only does it when its cold. Also did u gap the spark plugs properly, no good replacing them if the gaps are all over the place. Also i had it onetime where my fuel line was loose on the back of the passenger fuel rail, and it was causing the car to hunt badly around idle, check that hose and for any other fuel leaks maybe also.

[CommodoreVS]

No codes showing up and gapped the plugs fine. Used cleaning additives for injectors etc. Only when it's cold this problem occurs.. Hasn't not stalled yet, just annoying. When warm up after 15 mins driving it's fine? Is their auto choke in it that can cause this, if so where is it. Thanks

[slammedvz]

put new injectors in it, mine was hard to start when cold, good as gold when warm. cleaning add will not help if the injectors are leaking.

[baza]

could be fuel pressure regulator , on the fuel rail . take the vacumn line off the regulator and see if any petrol leaks out the nozzle. if petrol comes out will mean the diaphram is leaking , and regulator needs replacing. also check that the vacumn line is connected at front of manifold , behind throttlebody. and check the other vacumn hose next to it that goes to the MAP sensor on the firewall. if that does not help , you may have to change the TPS throttle position sensor on the throttlebody as they can cause idling problems. these things dont always show fault codes.

[CommodoreVS]

Thanks baza I'll try that out and let you know.. I have changed the IAC recently, got told not to touch TPS though from a technician..?

[slammedvz]

Tps is the same as a vn to vr v6 one, just swap it with someone you know is good.