Hey guys i drive an EB II with a sprint gas system and recently when i first start the car there is a rough idle, if i leave it for 1 minute then it will go back to normal idle. BUT when sitting at lights or at a stop on gas sometime my car shutters every 30 seconds and if it does that when i go to take off the car will lag, put off the line and then go back to normal after a few putts !

It doesn't do it all the time but it is really annoying ! What can i do? Also my 2 vaccum hoses that go to or near the heater tap are fine !

Do you run a simple mixer system??
Ie. A sprintgas LPG system. OR a system that runs a mixer 'ring' in the intake???
If you do here is 2 things I think could be wrong:

The LPG converter sensitivity setting

The sensitivity is basically the spring for the secondary gas metering valve.
If there is not enough tension on it you will experience over fuelling and all the symptoms you describe when the converter is cold.
When some heat gets into the converter it will behave better as the LPG secondary pressure will be more stable due to the heat exchanger of the converter being able to convert LPG from a liquid to a vapour more efficiently. When cold the LPG will have a tendency to want to come into the secondary chamber as a liquid still. In turn it will make your engine run stupidly rich and give the symptoms you describe.

Its quite in depth process to set converter sensitivity correctly, especially with EFI engines as they all run a LPG processor and stepper motor.
The stepper motor needs to be in 'tuning' mode to enable correct setting of the sensitivity of the converter.
I have posted a in depth tuning guide on the Ford Forums if you do a search in the LPG section you may find it. It is basically how to do a OMVL converter set up but the same principal applies for all simple mixer systems.

The other one I think it could be is you may have a converter full of oil sludge/ wax build up.
Our LPG quality is not the best in Aus. We have LPG with heavy wax content. This wax is oily in constitution when hot, but when cold it is like a thick wax sort of like chewing gum.
this wax will have a tendency to make all the moving parts in the converter move very slowly.
This can result in hard starting or poor throttle response and return to idle etc.....
The wax can make the secondary valve open VERY slowly when you need to accelerate causing the big flat spot you experience. And then when hot it all goes away.


If you are running a Impco air valve system this will not apply.
If you have Impco system I would think that you may have a dud primary or secondary valve, i.e.. not seating correctly???
Or a split diaphram or a stretched diaphram OR a mixer or converter full of oil sludge.

I know I have thrown alot at you but these are just some of the things I see regularly that will create the symptoms you are describing.
If you post a picture of your system I may be able to help more.
And also tell me if you have a multimeter and if you are proficient enough to be able to use your oxy sensor to tune with.

Hope this helps.
Cheers.

It is a Sprintgas System


By peaandham, shot with FinePix A600 at 2009-07-16

It also has a hose that connects to an intake like valve sitting in the air intake snorkel !