Originally Posted by
bee utey
Your excess enrichment may be due to there still being LPG held in the converter from the previous run. Was it switched off last on petrol or LPG?
Possibly the MAF is giving a poor signal, try swapping it. Cold starts are only controlled by the temperature sender for the ECU, its the 2 wire plug nearest to the thermostat just in front of the plenum, check it for tightness. Also check the vacuum hose on the fuel pressure regulator, a failed reg will dribble all of the remaining pressure from the previous run into the manifold.
To find out how well the petrol works on its own, just remove the 5 screws holding the lid on the Impco mixer, remove the diaphragm and spring, refit the cover and drive it. Those mixers can cut power by 25% easily. A different (ring type) mixer and matching converter setup will make a huge difference. Then there's sequential vapour injection, which I am now getting from the UK at around 1/2 the price I used to get it here, even before the $A tanked.
As for the random idle, try raising the base idle using the 3/16 allen key plug in the recess on top of the throttle body. A base idle of at least 500rpm gives the IAC motor more latitude to function without stalling.