Vz run rough

[Lumina05]

Hi guys, This is a long story so please be patient
I have a 05 VZ November last year from private seller. Have it converted to LPG on December. Since then my car runs very rough, the engine shudders & vibrates at idle and seems no pulling power.
I sent to my local mechanic I know & he change a new set of spark plugs and 1 ignition coil. The car seems OK for a month & starts vibrating again like before. The guy said the car running too rich & it is LPG related problems ( direct injection) because the car running normal on petrol.
I brought the car back to the LPG installer(Ezy Gas) & they change another set of spark plugs & new gasket. Same thing happens a month later. I came back to the Gas place & was told the oxygen sensors are not good & need to be changed. I bought the sensors from Holden & got a set of MACE manifold insulator and asked the guy to put them in. Half way home from workshop , the Check Powertrain warning came up.The LPG mechanics who did the job said that is because of the MACE gasket that causes the car running too rich when suddenly too much air intake due to the thickness of the gasket . He said that all the ignition coils need to be changed & the old gasket must be put back on. I got little knowledge about car so got no choice but do as they told. The car still runs bad.
Please post any opinions or advice on what I should do next. I am new here & just learn about MACE manifold insulator but cannot ague with the mechanics on whether its effectiveness & other problems of the car that they pointed out.

[bigdaddycool]

The insulator shouldn't cause a problem. Personally I think it's the opposite, it leans the car out due to the thickness of the wooden gasket, delays the air slightly getting to the cylinders.

Honestly I know nothing about LPG, I assume your car was retuned to suit the LPG?

I'd say it's probably all to do with your LPG conversion...... Like any car, major changes need major adjustments to the way the car works (with it's tune, fuelling etc.).

Given that you've got plugs, coil pack and o2 sensors needing replacing, i'd say ur car must be leaning out (stuffing the plugs, running the exhaust hotter etc).

I know with rough idle, it's all to do with the injector timing and how it's got to be smoothed out for the idle for it to idle smoothly.

So again........ dunno. Either way I'd say cars tune doesn't like your LPG setup.

[Benboy]

Take it back to the LPG installers, tell them you want it repaired and running reliably otherwise they can remove it and give you a full refund - including any out of pocket expenses you may have incurred trying to sole the problems. They did tell you that there was a guarantee on the product and their work - didn't they !! Good luck.

[Lumina05]

Thank you guys for taking time to give opinions about my car. The guy at EzyGas diagnosed the car & said 1 of the 2 O2 sensors was faulty and should be changed. I bought a new O2 sensors from Holden & have it replaced today. It was OK when I took the car but 1/2 hour drive the Check Powertrain warning came back. I don't know what to do now as they all deny their responsibility & keep blaming on my car. All the parts required to change have been done & the car is still shit.

[poweredbycng]

Does the engine behave the same on BOTH fuels? Have ALL coils and plugs been replaced? What spark plugs did they put in? Were the spark plugs gapped correctly (i.e. 1.1mm as opposed to 1.4mm for petrol)? Are there any signs of spark leak (i.e. marks on the boots on the coils)? Have BOTH oxygen sensors been replaced? Is your battery in good condition? Did your installer completely recalibrate the LPG system after replacing plugs / coils? Have you tried resetting the ECU (i.e. disconnecting the battery overnight to reset the fuel trims)? Is the ECU fault coding?

[Lumina05]

All the parts mentioned were changed including genuine ignition coils, spark plugs, O2 sensors. I don't know about the gap for the spark plugs or tuning for LPG but I assume they are gas installer specialist so they should know what they did. I have tried disconnect the battery but the check powertrain warning came back after a while. When diagnosed last week, the code they found was 1 faulty O2 sensor . That was changed yesterday but the warning came back after 1/2 hour later. It's look like the gas system has fried up the O2 sensor rather than I was lucky with a faulty one.
I am going to bring back the car to EZY Gas one more time today to see what else can they say about this.

[vrod]

I Had a simillar problem with my car. I had the Gas Guru come out to my place and sort it out for me
all it was in the finish was a software or firmware problem he knew exactly how to fix it.
I can try find his number I think i still might have it somewhere
Good Luck
Vrod

[db_notso]

incorrect spark plugs or incorrect spark plug gap
OR
get code form the car for the light on and post it (likely misfre code will be like cylinder#)

if runs fine on petrol and doesnt miss under load likely a air/fuel metering issue with the lpg ecu/sensors

i would personally check engine codes before going any further with replacing random parts and hoping
which is what sounds like is happening

[ricy_12]

Exactly what kinda gas system is it? Eg, Carby Gas, Vapour, Sequential?

[poweredbycng]

It'll be a Sequential Gas Injection system for sure on a VZ. Mixer-based systems are not legal.

I'd say that most likely that if the car is running 100% correctly on petrol, the installer has been slack and simply put the car through an "Auto Calibrate" and not finalised the calibration correctly. The "Auto Calibrate" feature on the software used to configure gas injection systems will only give you a approximate tune that will not be precisely accurate and may have some 'rough spots'. It takes more time to precisely tune a gas injection system to suit a specific vehicle and requires quite a bit of fiddling around with the custom tuning feature in the software while monitoring air/fuel ratios and other parameters.

Failing that, don't forget that running an engine on LPG will make it more spark-sensitive. I've said this many times before: an ignition system that is 'marginal' for petrol will be 'unacceptable' for LPG operation.

[ricy_12]

since when have mixer-based systems been illgeal?