Does LPG affect O2 sensors differently?

[capt jack]

Regulars on here will have seen quite a few threads recently on poor idling on LPG, engine management lights and fault codes - all with converted engines.

The common themes are that the cars run fine on petrol, but not so well on gas, and that the problems are intermittent.

My own V70 has ben playing up for a few months now. It's been hunting at idle, running rich, running lean, triggering fault codes etc etc - always on LPG.

Pistrix and Volvobaggen have reported similar issues, albeit with new conversions rather than my 280,000 miler!

My problems have been improved (but not resolved) by fitting new injector solenoids and a new gas regulator, together with a series of re-maps.

Others on here have reported various repairs - new temperature sensors, re-maps, etc etc, again which have given some improvement but not a complete cure.

I'm now begining to wonder if it's possible that O2 sensors work the same with LPG as they do with petrol?

My car now runs absolutely fine on petrol, and for most of the time on LPG. But sometimes it throws a fault code - always 2-2-1. I can go for hundreds of miles without a light, or the light can pop on literally every few hundred yards. There is no pattern.

According to the fault code table I have this means 'Lambda Operation; also Heated oxygen sensor (mixture too rich under part throttle)
/ long term fuel mixture too weak in part load stage'

In other words, the Lambda sensor might be faulty, or the mixture might be too rich, or it might be too lean!

I ruled out a faulty sensor, because it's OK on petrol. But I've had the LPG re-mapped and as far as we (the LPG guy and me) can see it's absolutely spot-on. But with the fault code being so random, I'm begining to wonder if this is the first sign of the Lambda sensor failing? Trouble is it's not a cheap option just to fit another, so on a 16-year-old car with almost 300,000 miles up, I'm reluctant to start swapping bits just to see what happens.

Could it be that when Lambda sensors start to fail, problems are more apparent on LPG than on petrol? If that is the case then I'd feel more inclined to renew the sensor.

The thing is, this might also explain some of the other problems reported on here. Pistrix and Volvobaggen have new conversions, but the problems are the same as mine. But if Lambda sensors are more sensitive to LPG than they are to petrol, it might just explain things regardless of the age of the conversion.

Any ideas anyone?

Cheers

Jack

PS: I ran the local main dealer yesterday, but they said they couldn't help at all because they haven't got the right diagnostic software any more!

PPS: I am tempted just to ignore the fault light, but I've found that if I do then the car starts to run a bit ragged on LPG, then not all, then the petrol performance starts to suffer, presumably as the petrol ECU tries to puzzle out what's happening. The only solution then is to disconnect the battery and wait for 10 minutes!