Egnine misfiring in the morning

[giorgos3924]

lpg is like cng.
so, why when the lpg system is on (car work with gas and no petrol) then the problem resolved?

Each time (in the morning - cold engine) where i starting the engine (start with petrol-unleaded ALWAYS) there's misfiring in the fall of rpm.
I start with key and it work with normal idle (around 1200rpm)
and when i touch the accelerator then raise rpms and when fall (realease accelerator) i see the misfires around 500rpm for few second!! and in few second the idle come back again in normaly (1200-1100rpm)
When i start the car it have no power and probably it get off!!
then i start engine again...
and again i try to start...
When it starts, it haven't power to accelerate! like VERY VERY LOW horsepower and suddenly in a few second (about 2-3) time it get the lost power back and accelerate rapidly (hardly - badly - quickly)
and in a few minutes when the engine is warmed up enought
the LPG kit turned on! and the engine works with gas!
then, the problem disappear! the car work PERFECTLY!
Then IF I TURNED THE ENGINE MANUALY BACK IN PETROL-UNLEADED AND THE ENGINE HAVE NOT WARMED UP IN OPERATING TEMP THEN THE PROBLEM (LOST POWER) BACK AGAIN!
and when it warmed (operating temp - normaly temp) the problem solved and the engine works PERFECTLY also.

[The_AirHawk]

Originally Posted by jeffdaman

What is LPG? I'm in the United States and it's a new term to me. That said the mass airflow would be my guess. I believe the mass airflow acts like a choke used to and your engine believes it's already warmed up. If it idles fine until you tap the gas then that's all it really can be on a normal car. But I don't know what LPG is so something in that kit may also be causing the computer to believe the engine has reached it's normal operating temperature.

LPG = Liquified Petroleum Gas: "Propane".

Nearly every non-electric warehouse-forklift in the country uses it. It used to be quite popular in the late-'70s and '80s as conversion-kits for cars and trucks after the "first" Gas Crisis. (mostly pickups - they were the easiest to retrofit a large propane tank to)

It is still around - just not as prevalent, and the manufacturers of the kits have taken great pains to hide the tank(s) - you probably cannot tell at-a-glance an LPG-kit from a standard vehicle.

never have seen so many !! in my life lol

[Albinus]

Originally Posted by jeffdaman

What is LPG?

Liquified petroleum gas. Can be anywhere from 100% propane to 100% butane. Where I am LPG is normally pure propane, and 99% of fuel stations sell LPG - goes for roughly half the price of regular unleaded. Problem is, because of its lower density, you need more fuel to drive the same distance (although propane has an octane rating of 115, so with timing advancement you can get quite a bit more power). In fact, one in ten vehicles here is capable of running on LPG. This is opposed to CNG that is compressed methane (natural gas)

There are many problems, however. The first is higher fuel consumption. The price spikes during Summer as the northern hemisphere demand bites, can be A$1/L that gives no benefit economically. Secondly, while some cars come equipped from the factory with LPG induction (the Ford Falcon and GMH Commodore are the most popular), most run an aftermarket system that can cost up to A$5000. The cheaper systems run a mixer bubbler, that is much less efficient than direct injection. The third problem is due to the high octane, things run hotter, and two things that die more frequently are spark plugs and ignition leads. Most converted engines require upper cylinder lubricant to help reduce wear to manageable levels.

As for the OP, I'd be interested to check the resistance of the leads with a voltmeter, and the actual coil (electrically, not with water). If the problem varies between fuels it could very well be an issue with the conversion kit.

[giorgos3924]

may can it destroy the coil or ignition leads??

in the moist weather (like today) the car have some missfires on moving! like ignition failure! for less of one second.
in the LPG this is more visible! in petrol maybe is invisible (no feel anything)

[giorgos3924]

i have replace the coil.
i have replace the ignition leads.
i have replace the petrol pump.
i have replace the filter pump.
and the problem has not solved!!
it is more smoothly now... buy it still!
what can i do now?
i have put a half bottle stp petrol injector cleaner before the replaces (one month ago) i drive with unleaded for 100km and i get the same little difference (smoothly misfiring).

[Albinus]

Originally Posted by giorgos3924

what can i do now?

My choice would be to take the car to an auto electrician that has knowledge of gas conversion systems. You've effectively ruled out the issues I would have suspected - glad to see it's running smoother - but a good auto electrician with all the tools may be money well spent.

i have put a half bottle stp petrol injector cleaner before the replaces (one month ago) i drive with unleaded for 100km and i get the same little difference (smoothly misfiring).

I personally dislike the little bottles of injector cleaner; a 200mL bottle in a 45L fuel tank isn't really effective. I've always used lacquer thinner, 4L in 20L of unleaded and run the car for about 200KM on it. Failing that you can get your injectors cleaned ultrasonically, the stock ones in the Accent are very, very well built and don't tend to die, just gradually gum up with deposits.