Have I been sold a duffer 2 LPG Vectra, HELP!

Code P0134 O2 Circuit No Activity Detected (Bank 1, Sensor 1) Code P0571 Brake Switch A Circuit

Considering that most of the codes related to a bad O2 sensor, I am surprised it was not changed. A bad O2 sensor can caused stalling, even at high speeds.

In message , snipped-for-privacy@yahoo.com writes

Usually best to sort out the problems on petrol first. Unlikely that a gas issue will affect running on petrol.

You might want to check the wires to it first though.

I dont have any direct experience with factory fitted gas, but I've been running converted cars for some time now. The first thing I would look for is if you have a leaking blowback suppressor. This is a device that lets out an explosion in your inlet before (hopefully) it destroys anything.

Inline ones look like a metal ringpiece up to 1" wide with a rubber band around it. they have a flap inside that moves aside under induction,but slams shut under blowback and vents the gas past the rubber band. if you have one then check that the band is forming a nice tight seal. might be that its a bit sloppy, and taking your foot off the pedal provides enough suction to seal it again.

other kind look like a hinged circle on somewhere flat like an air filter box. overpressure lifts the flap and vents, usually a spring pulls it shut. again, check for leaks.

I find the thermostat bit interesting. if its faulty and running cool then the ecu will treat the engine as just started and will adjust the mixture as if just started, i.e. rich. you say it goes up to 90 then fan comes on. is this stationary, or will it do this when driving sensibly (not thrashing it) on level ground?

another thing would be to have an emission test done. on lpg the petrol injectors should shut down. but the fuel pump usually doesnt so they are still pressurised. if worn they will leak. this plaged my old range rover. result was increased consumption and very rich running. if the HC is high when on gas then you might have bad injectors, but sometimes just running an injector cleaner in the tank can help. didnt with me. my solution was to fit a switch to manually shut down the fuel pump myself. also a handy immobiliser....

Hope this gives you something to go at.

Mike

Rubbish!

The o2 sensor can only influence fuel trim by around 15%, and using full throttle will cause the ECU to switch to a fixed fuelling map, and either a) totally disregard the o2 sensor, or b) more likely on very recent engines; use a fixed map which it has trimmed from previous experience.

It would appear the OP still has a long term fuel mix rich mix on gas, but not excessively so, according to his o2 sensor voltages.

There is an underlying problem which is causing the cut outs, probably a sensor or wirng problem.

Alas he doesnt seem to be able to find a well experienced enough technician who is familiar with the LPG conversion to sort the root cause, although fixing the thermostat and o2 sensor was a good start.

The LPG ecu may well need reprogramming, as the tuning doesnt seem quite right either.

Tim..

Tim, I have over 30-years experience in the diagnostic business, and will restate the claim that a bad O2 sensor can, and frequently does , cause high speed engine stall. A classic case would be the Rover group. An after-market universal O2 sensor fitted to a Rover, have been known to cause the ECU to fail completely, and only dedicated O2 sensors can be used. Whilst the vehicle is a Vauxhall, a short in the sensor can intermittently spike the ECU.

The fuel consumption is dismal and error readings show rich mixture. This is affecting Gas and Petrol.

Just a thought could there be an air problem?

Is the air filter clear? Is there some other restriction to air flow.

good luck

H Matthews

There is a good possibilty that you are correct. Brake sensor feedback is a relatively new idea on Vauxall cars, and from the mapping it seems that this switch can cause the ECU to switch off the injector circuit, much the same way that a closed TPS on a decelerating engine will cause the injectors to close. That is the problem with newsgroups. We don't get hands-on to the engine in question. A decent analyst would get streaming data during a test drive, and the fault would be obvious.

Thanks always impressed by the helpfulness and the knowledge on usenet.

Took it in today after getting the ECU light on again, the following faulty codes were read:

P0134 o2 Circuit No activity detected (bank 1 Sensor 1) P0170 Fuel trim bank 1 malfunction Both same as last time:

So Mechanic did what most of you suggested:

2] executed me140's Brake light fix. Me140 I owe you a quid!!!! It seems to fix the power loss problem

However I am still not that happy about the fuel consumption Im only getting 5 miles/litre on the Motorway????????

This was measured by filling the car to top, then driving 50 miles and refueling back to top.

I will re-investigate and re-measure but still not satisfied with my result.

Further investigations were also carried out by mechanic: The car drives nice the spark plugs were examined they very clean. the power compression was measured on each

spark and was spot on 1200 (??). Another flow (maybe fuel) was measured that was spot on at 3.8... But couldnt figure out this bad fuel usage??

thanks to all again were getting there, one thermostat down, One Lambda down,and a brake switch reset.

So any other suggestions??

If his diagnostic machine reads data as well as fault codes it would be nice to know what the short term and long term fuel trim readings are. I wonder when last time LPG pressures were checked too?

If he's using 1 litre of gas per 5 miles, its got to be running pretty rich which surely the o2 sensor would pick up on. Plugs dont blacken on a rich lpg mixture as they do on petrol.

Has the lpg gas pressure been checked, and can you confirm what the mpg is like on petrol?

Tim..

Well you don't say how you drive!

If I do 80ish, I can get my Volvo 850 to return 21mpg which isn't that different to your 23mpg. On the other hand if I drive a nice 60, then I can return nearly 29mpg.

What I will say is that 50 miles isn't enough to get a good indication anyway as filling pressures etc may vary. Go empty to empty.

David.

For reference:

my 04 Vectra LPG has returned 5.49 m/litre over a two month period. I have been unable to get a sensible measure on fill to fill because full is never the same twice. However don't be downhearted. 5.49m/l at 36p /litre is equivalent to 14m/l (63mpg) at 92/l for petrol.

Matthews

Is that gas or petrol? If petrol and its not a T5 then its very heavy. At a steady 80, ours does 34-35mpg.

Tim..

The petrol thing on the dash used to report 28mph on petrol and then on gas I usually get 26mpg.

You don't say what car you have specifically but I'm not sure the comparison with the T5 would be equal anyway. I used to have a Saab

David.