Why does my lpg car backfire

Login Sign Up. Your have items in your shopping cart. Forum Index. Hi all, Just recently moved out to this great country and bought an 88 Pajero k KM's to run around the countryside with the kids, however I'm having some bother with the LPG system that came fitted to the car.

The engine runs as smooth as you like when running on LPG however the exhaust makes a 'bubbling' sound whenever I take my foot off the accelerator. When I switch over to petrol the car initially picks up nicely and runs for a about 3 minutes before there is a loud pop from the exhaust.

Within the engine bay it appears that someone has disabled the emissions components. For instance, there is currently no hose from the Air Injection Valve to the vacuum Outlet this is the thin hose with the one-way reed valve.

Also, the 4-Port Thermal Valve located in the Thermostat Housing only has one hose attached to it - the others are open! Is there a requirement to modify the emission control hoses when fitting LPG or has a previous owner 'fixed' a more serious underlying problem?

I have taken the car to two mechanics however all they seem to do is adjust the timing and charge me a small fortune! I found that with a extended rotor I lost a great deal of usable power from coil.

Notice a great deal of power lose with the extended rotor and this backed my theory of electrical power lose available for burn, as torque was not there straight up with the ext rotor, car felt like it dropped a cyl worth of power, so I have a new bute ext rotor for a emergency spare.

The smaller extended rotor gap requires less energy needed to bridge the gap and as a result less energy is expended across gap. I found that using a std rotor and the smaller "iridium plugs" plug gap gave me a setup that worked for both fuels better, without backfire issues. The increased energy available for plugs to burn fuel, either fuel, seemed to be working a treat.

I have no flooding issue as iridium plugs exposed finer electrodes and concentrated spark nicely. Iridium handles heat alot better than std plugs, 10 fold "so to speak". The only problem I have is the perceived problem of elec power jumping between leads and causing a the odd miss fire whilst driving. I noticed the burn marks on leads and that's why I recon this is the problem at hand and was seeking to find if anyone else noticed something similar.

Epoxy GT30RT coil. Pertronic cam sensing. NGK iridium. Interesting read Im not sure I fully support your findings but it has intrigued me enough to do some research of my own on the subject. I have however had a similar problem with ignition leads which I corrected by installing high performance low resistance leads ohm from memory.

Installing low resistance leads in your setup would not go towards supporting your theory of resistance causing the release of unused energy however so it may not be a path you'd choose to take. Good sound advice given here.

If an LPG system is tuned correctly, putting your foot on the throttle at start up would cause the air fuel ratio to lean out thus causing a lean out back fire. My friend Patch!!!! Welcome To LandyZone! Cookies Welcome Guest. Lpg Backfire??? A couple of days ago my Disco blew back through the inlet side of the engine whilst I was running on lpg at 90mph down hill wind at my tail very fast but quite a low load.

It exploded the air box and made the engine run very rough at tick over. What causes this backfiring and how can I prevent it happening again. Thanks in advance Pete -- "Reason has always existed, but not always in a reasonable form" Groucho "Those are my principles, and if you don't like them Highbeam , Dec 19, If it's hotwire, check the wire grille thing in the upstream side of the AFM. The conditions are not what I'd normally expect for a backfire.

You don't say what system it is, so no advice from me there Austin Shackles , Dec 19, I will have to get under the bonnet and do some research -- "Reason has always existed, but not always in a reasonable form" Groucho "Those are my principles, and if you don't like them Is the LPG system fitted with a "flapper" blow back valve?