Range Rover Classic LPG Lambda sensor

I have a 1990 range rover 3.9 auto. It was converted to LPG several years ago.

It has always had an oscillation in the idle speed when running on gas. It oscillates between 700 and 1300 rpms. It doesn't do this when running on petrol.

The LPG system is an AEB/Leonardo 175.

I have the software and cable to control the system. I was able to sort the oscillation in the idle speed by selecting a different O2 sensor type. It was previously a 0-1V and I changed it to 5-0V. The idle speed flattened out. It ran fine like this for a few weeks.

Now the range rover suddenly started running badly on LPG. When I checked the system it indicates the O2/Lambda sensor has failed. Now this could be a concidence and it has just failed with age, but my suspicions tell me otherwise

Can anyone else confirm the correct settings for the O2 sensor? The old one has four cables. Two white, one black and one grey.

Any help is much appreciated.

its 5-0v for the lambda, have a look here on simon hobsons page, he is a reguler at LPG forum(google it!)

i have the leo controller to and mine sits between 500 and 750 rpm.

gavbriggs said:

its 5-0v for the lambda, have a look here on simon hobsons page, he is a reguler at LPG forum(google it!)

i have the leo controller to and mine sits between 500 and 750 rpm.

Click to expand...

Thanks for the response.

Can you confirm that your O2 sensor is set as a 5-0V as the one indicated on simon's page is a 0-1V?????

Cheers

Sounds like the sensor may have been at the end of its life when you reset it. I would put it on an osillascope

I'm not suprised its gone wrong.it sounds like the actual sensor fitted is a 0-1v Zirconia one,these tell the ecu that 0v is lean,.8v is rich. If you have now told the Lpg ecu that a 5-0v Titania sensor is fitted they work the other way round,5v is lean,0v is rich. Plus the fact that if the fitted sensor was working,the highest voltage you would get is .8-.9v,not enough for the ecu to see it as crossing the threshold to widen or narrow the injector pulse width for closed loop operation,and if it could it would be back to front anyway.
Scoping it is the best answer as suggested,to see if the sensor is capable of switching,once you can achieve that then you should be able to trim the ecu's fuelling to get the correct mixture.

dunno bout all that, i was fiddling with mine and couldnt get a good reading from the 0-1v type(mines a p38 tho!!) then set to 5-0v and all is fine!!!

simon is very knowledgeable and helpful on the lpg forum. he seems to know his stuff!

i couldnt find any other reference to the voltage of the lambdas on mine so posted on lpg forum and got a response which worked.

gavbriggs said:

dunno bout all that, i was fiddling with mine and couldnt get a good reading from the 0-1v type(mines a p38 tho!!) then set to 5-0v and all is fine!!!

simon is very knowledgeable and helpful on the lpg forum. he seems to know his stuff!

i couldnt find any other reference to the voltage of the lambdas on mine so posted on lpg forum and got a response which worked.

Click to expand...

Gav,thats cos your P38 has a pair of 5-0v Titanias,a 93 Classic will have 0-1v Titania's for its engine ecu,but the LPG system would probably have a seperate 0-.8v Zirconia as a third sensor in one downpipe just for the LPG ecu to read.It would be very unusual to have a 5-0 volt third sensor as they are much more expensive LPG systems use the cheapest cr-p they can get away with.So if it does not have a third sensorand piggybacks one of the petrol ones the correct setting in the LPG ecu would still be 0-.8v.

guess he'll have to fiddle with the settings and find the best setup. pretty much what i did!!! i did save original settings even tho they were wrong just in case!!!

Hi Chaps,

Sorry to dig this one up but I'm having similar problems with the same AEB system on my 3.9 classic. I'm really after what the settings should be, lambda type, open loop, ground simulation?

It seems whatever configuration I try it still through a out errors. It was running fine as an open loop system with 0-1V 02 sensor, but started throwing a fault so fitted a brand new Walkera sensor and has made no difference! Tried 0-1v & 0.8-1.5V no difference.

My LPG piggy backs from the OEM 02 sensor in the o/s bank. If any one can provide a screenshot of their settings on this engine with this Leonardo LPG system would be a godsend!