GAS idle problems

[crossy]

i'm going nuts here,

i picked up a recently rebuilt 202 on gas with a vh comodore surrounding it. needed for parts for an engine swap in the landy bla bla bla..

engine specs.
holden 202, 12 port with vk efi manifold. straight gas, stock throttle body and como v6 mixer. landi complex converter.

i need to get this running nice and smooth as the head, lpg and intake manifold are going onto a brand new motor. i dont wont any tuning dramas whilst running in.

i can tune it so it idles very smooth and at low revs no problems, but as soon as i take it for a drive, after about 1 min it wont idle
retune idle mix - same thing happens? (done this many, many times)

when running under throttle the car goes well with heaps of power.

the idle mix screw is very touchy - 1/8 of a turn will be all it takes to go from smooth idle to bag of ****. (same on both converters)

i have changed the converter, this made no differance.
changed gas feed line to the mixer again no differance.

tripple checked for vac leaks ect - all ok
converter is nice and hot

the only thing i can think is the mixer is too big for a 202?
the mixer is a basic ventri type- inline just before the throttle body.

any advice appreciated.

[George130]

What is your idle bypass. Is there a solenoid or a strait pipe. Our ford had the solenoid, very troublesome. I have had mine removed and was told it's the first thing the cabbies remove. Also open your mixer and make certain the diaphram slides smoothly. Backfires can bend the spindle which causes it to jam.

[crossy]

thanks Edd,

the mixer has no moving parts - its just a ventri with slots to mix the gas.
no idle bypass fitted.

pulled both converters apart, both seem 100% ok.

i'll try fitting a straight pipe into the intake instead of the mixer and see how it goes.

[George130]

The mixers with no moving parts means like you said its not the prob. I wouldn't toss the mixer yet. Try poring water over your converter when its running.THen look for bubbles. The air leek could be from there. For a while with our ford I used to have to stand next to the car while turning the engine over (Hand thriough the window turning the key) while I hit the primer button on the converter. Used to drive me mad. I can pose your probs to the guy who fixed my car and get back to you tomorrow on it.

[Michael2]

what air intake have you got?

My 2.25 always stalled when coming to a stop after a high revving run (freeway) and this was more pronounced if an air ram was fitted. The LPG guys ran a pipe / hose from the air cleaner to the atmospheric side of the convertor (tapped a hope where the diaphragm is). That usually worked for them, but my tempremental beast required another t-piece going to atmosphere.

The problem lay from going full throttle to suddenly going to closed throttle, I could hear the LPG cutoff solenoid clicking frantically as I'd come to a stop, unsure if it was going to be open or closed. Anyway, it works fine now as long as I don't have an airram on the snorkel.

I should try it again with the weber and an air ram to see if it was a tuning problem specific to the Zenith. A change in convertor earlier hadn't made any difference to these characteristics.

[crossy]

thanks for the help.,.

turned out to be the intake duct i was using.

i was using a piece of flexible pipe with a filter on the end as a temp setup.

changed to solid ducting from a v6 commodore - all good now.

This gas stuff sure is tempromental. :?

[George130]

Originally posted by crossy
thanks for the help.,.

turned out to be the intake duct i was using.

i was using a piece of flexible pipe with a filter on the end as a temp setup.

changed to solid ducting from a v6 commodore - all good now.

This gas stuff sure is tempromental. :?

Yea but when you get it running correctly its sweet. Also Gas loves turbo's :twisted: :twisted: Just make sure you can get enough gas to it. A mate used to get pulled over all the time because the cops thought he had a rotary in a subaru leoni. Pop the hood and there was a stock motor with the spare on top. What they didn't know was remove the spare wheel and there was a turbo. Only prob was after 10 mins of flat stick it would stop as the lines to the converter would be frozen but that at least allowed you to peal your head of the rear window and regain your senses.