Cold Start Idling

[WIL35]

Each time I start my 4.2 I have to hold it at quite high revs (1500+) otherwise it stalls. If it does stall, it won't restart straightaway because it is flooded.

I had a 4.2 before that I could start without holding the revs high, reverse from the garage straightaway and leave it idling while I closed the door. My current one would just stall if I tried that. I just read the following (thanks Juddder!) in another thread:

'On cold start, the ignition timing is advanced which takes care of the cold-start fast idle, and the timing is gradually trimmed as the coolant temperature increases. It's important that the butterfly area is cleaned every service to maintain the idle speed...it shouldn't be raised just by opening the idle speed stop screw since this ruins the relationship between the rate of opening of the butterfly and the expected change in airflow possibly resulting in uneven slow speed running (for each incremental increase in butterfly angle, the rate of change of airflow decreases).'

Could it be the 'butterfly area' isn't clean enough? I am reluctant to clean this having read another thread that suggested the air flow rate can be adjusted by cleaning this area around the butterflies.

I'd prefer it (as would my neighbours) if I didn't have to hold the revs high for a few minutes before moving the car out of the (noise amplifying) garage!

Any ideas?

Thanks

[CerbWill]

Essentially your engine setup is probably wrong. I'm at work so I don't have all my favourited threads to hand to link to but plenty of advice on engine set-up procedure is available with a quick search. I'd start by checking the airflow into each trumpet with a carb synchrometer to confirm theyre all equal. Its also possible the throttle pots are not set correctly. TP percentage reported to the ECU has an effect on ignition timing so it may the ECU has advanced the timing as much as it is permitted by the coolant temp compensation map, but the 'base' timing dictated by throttle position, is retarded enough that even max permissible compensation isn't enough to get the engine to idle when cold.

[WIL35]

Thanks. My air synchrometer should arrive today and I already have the software on an old 90's laptop that I used to use.

As far as the process order is concerned, is it as follows:

Warm up engine and return to garage
Remove airboxes
Start engine, leave idling and plug the synchrometer into each inlet, note readings (should be 4-5)
If there is a difference between the banks adjust the (now rose jointed) rod that links the banks
If an individual inlet air volume is reading lower than the others on the same bank, clean around the butterfly, to see if that can bring it up
Switch off engine
Plug in laptop
Adjust idle throttle stop completely off
Adjust throttle pots to read 15%
Adjust idle throttle stop to so both throttle pots are reading 19%
Reset adaptives and start the engine
Adjust idle to 950rpm
Check adaptives, should be below 10
If the adaptives are over 20 and the air volume is equal between banks, is it a case of tweaking the throttle pot on which ever bank has the high adaptive figure?
While laptop is plugged in, check all the other readings (lambdas etc) and make sure there are no other fault codes.

Thanks