Engine RPM dips on cold start

[SKNOT9]

Hi guys. I have been having this problem which has been gradually getting worse, to the point of stalling now. When i start my v6 auto VS the engine rpm dips for about 3 seconds straight after it has started. It now stalls if its a really cold morning. If I turn it off straight away and start it again it is fine and starts normally. If i have left it for a couple of hours, once again it starts normally, its only if i havent started it for a day or 2. Has anyone had this problem before? recently serviced, cleaned IAC valve. Also, when i put on a bit of throttle to help the situation when it is dipping, it doesnt really make much difference, it will still dip to about 500-600rpm, which tells me it is probably not the iac valve because as soon as you put on some throttle, it shouldnt have any effect anyway. Someone help i have run out of ideas!

[Cheap6]

Leaking injector(s)?

If you remove the rail and run the fuel pump - bridge the relay or turn the key on and off a few times you might be able to see which one(s) by wiping the injector tips with a piece of paper or even a finger if they/it are bad.

Another fuel pressure leak, possibly inside the tank. You would need a gauge to check the pressure but if you trurn the key to on then off, maybe a couple of times, to build fuel pressure before starting then the car starts and idles OK that would be a clue.

[jatsvl]

dirty throttle body and/or plenum chamber?

[SKNOT9]

ill check out the leaking injectors, i have tried turning the key up a few times to build pressure but it doesnt help. Cleaned out the throttle body and plenum chamber, didnt help. Someone has said could be a maf on its way out, is this possible?

[James39]

DId you clean the IAC?

[reeceo]

exactly the same as mine. does your revs rise when you push the brakes in when you are in park?

[SKNOT9]

Na pushing the brakes has no effect on mine sorry

[Cheap6]

exactly the same as mine. does your revs rise when you push the brakes in when you are in park?

That will be a leak in the brake booster somewhere. Possibly the booster itself or the one way check valve.

[The1]

Generally this issue is a memcal tune one and can be easily fixed with an update.

Holden Changed some of the cold start fueling in some memcal versions about half way through the vs series, they leaned the fueling out below 20deg C coolant temp, no idea why they did this but in winter cold starts the engine now chugs for a second or two when first starting up but doesn't do it till it cools right down again the next morning, summer time its unaffected as the coolant doesn't get below 20deg.