Hi,
My el fairmont is running terribly and its hard to diagnose the problem!!
On gas it runs fine whilst driving with a small miss at idle and when driving when i back off the revs it does a little rev up then goes to idle again with the little miss.
However on petrol it runs atrocoiusly misses and the exhaust smells as if it running rich. It won't idle on petrol and generally runs terrible!
it's strange as it runs OK on gas please help!

Sounds a bit like my Fairlane. Still haven't had time to get to the bottom of it either. What I plan to do is this when time allows. First is to check fuel pressure and delivery. I have already put a new fuel pump in as the old one was getting noisey. As with a lot of dual fuel cars, lpg is used majority of the time and this causes problems for the petrol side of the car. Your fuel can go stale if its not used for a long period of time. The fuel pressure regulator can gum up or the seals can dry out. The fuel injectors can clog up and require cleaning or exchanging.

I am going to check for approx 40psi of fuel pressure at the fuel rail and also check that the fuel pump can deliver well over a litre of fuel in 1 minute. If fuel pressure and volume are good then I'll replace the fuel injectors on an exchange basis. I have already checked for codes as per instructions on this web site and all was good. My car runs well on gas so not too many things can be the culprit.

If you intend on checking fuel pressure and volume yourself, ensure engine is cold and have an assistant crank the engine for you so you can hold a container under the fuel line. Fuel pressure test kits can be purchased from that auction site on the internet (you know the popular one) or form Bursons etc.

Last edited by alfy12 on Tue Mar 03, 2009 1:06 pm, edited 1 time in total.

the MAP sensor couldve shat itself. try swapping another one in and see if that makes a difference. i think theyre about $5 from a wrecker.

Being on gas i would check the ignition leads and the spark plugs also check the rotor and distributor cap.Gas requires good condition of the sprak ignitiion system to run efficiently.

When you turn it back to petrol it would obviously run worse due to the gas treatment to the ignition system.Gas is hard on the leads and plugs.

I would check the resistance in the ignition leads also check for black powder residue inside the plug and cap ends.

Check and replace spark plugs with the appropriate gap to suit gas.

Being an EL check the distributor cap for cracks and or build up on the posts.Also check the rotor for cracking.

Check the bolts on the inlet manifold are tight,also check for a broken inlet gasket (very common) simply by spraying water over the inlet gasket whilst engine running you should notice the engine revs will change if it is leaking.

Good place to start.

my ef ex taxi had same problem. gas fine, petrol felt like it would stall, clunking and shaking etc, rich smell from the exhaust. i replaced the injectors and fuel filter. runs sweet as now.

+1 map sensor, or faulty wire back to ecu on oxy sensor after the conversion. possible earthing prob too.