04/05 Avalon idle problem

[hvymetalalchmst]

g'day all from australia!

my dad owns (i think its '05) toyota avalon, which has been gas converted. It has been running fine until just these few months when i have noticed late at night, that when he turns into the driveway, the car kind-of sputters. it sounds fine, nice idle but there sounds like one cylinder will inconsistently and randomly put out a little more exhaust gas once maybe twice a second giving a little 'putt'. But it only sometimes does it when its cold - when warm, nearly always. does anyone know how to fix this problem (we think maybe valve timing, though it iss vvti [from what i can remember]).

The second, and probably more important question, is: where is the engine idling adjustment? he says he found the screw next to the inlet-throat-thingy which the gas pedal cable connects to, but its not what he is looking for. i think he mentioned that he wanted the cold starting idle up (if it exists) because it struggles to start well: it needs to rev pretty high up like ~1500rpm for 2 secs before it will keep alive and then its fine. this problem only comes up when the engine is cold starting. when warm, its perfect.

If anyone knows what hes talking about, or better yet, knows how to fix this problem, it would be much appreciated.

thanks,
rex

oh, and its a 3.0L v6