sussex-landy Posted November 5, 2011 Share Posted November 5, 2011 I have just had my Range Rover 4.0 2001 fail an MOT on emissions for Lambda readings which the MOT guy said could be exhaust leaks ??? which I find curious as there is no leaks i can see in the exhaust and you would hear it blowing. My printout shows the following. CO - 0.00 % vol HC - 1 ppm Lambda - 1.151 fail min 0.950 max 1.090 Seems strange as everything else is perfect to a point I would question his machine as I cant believe I get a 0.00% CO on both fast idles. Garage said put some redex in a blast it up the motorway which I am going to do on Sunday on a 400mile round trip. Also going to clean the air filters and tighten exhsudt manifold and anything I can see related to air or exhaust gases. What I dont understand is how a leak makes the lambda worse and if its an exhaust surely it blows. When my S3 had a leaking exhaust you could hear it popping. Thanks Robert Quote Link to comment Share on other sites More sharing options...
Range Rover Blues Posted November 5, 2011 Share Posted November 5, 2011 My mate is a tester and he always recomends a change of oil too. Quote Link to comment Share on other sites More sharing options...
sharpy1980 Posted November 5, 2011 Share Posted November 5, 2011 I had the exact same prob with my wifes car a couple of years back with lambda only being high and I tried a spare lambda with no effect and it turned out to be a small leak on the inlet manifold and found hairspray or household polish useful to locate it. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted November 7, 2011 Share Posted November 7, 2011 Exhaust leaks would do it - air is richer than exhaust gas (more oxygen in it) so throws lambda readings out. Quote Link to comment Share on other sites More sharing options...
RocksteadyEddie Posted November 7, 2011 Share Posted November 7, 2011 Little leaks introduce more air, making the gas leaner. So the lambda richens it all up thinking the engine is running lean. This of course makes it too rich which is why the car failed. Check manifold flanges, you have to take them off to do this. A big job. This May I had mine off, angle ground a nice clean join., and welded all the cracks I found. Job done. Good luck, it's a two day job ( unless you have a ramp) Quote Link to comment Share on other sites More sharing options...
SteveRK Posted November 7, 2011 Share Posted November 7, 2011 Isn't the exhaust system under positive pressure though? Quote Link to comment Share on other sites More sharing options...
sussex-landy Posted November 7, 2011 Author Share Posted November 7, 2011 Thats what is confusing me I would have expected exhaust gases to get out and not so much air getting in. I am going to see what the readings are now I have done a long trip to wales and back as my mpg's got better after a reset the meter every 50 miles after starting at 21.x mpg and now 26.x mpg so I am guessing something got cleaned out. Then I will start working around the exhaust in more detail, I couldnt spot anything when I checked it over at the weekend. robert Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted November 7, 2011 Share Posted November 7, 2011 Isn't the exhaust system under positive pressure though? Only when a pulse goes past, as the pulse moves past a leak there is a low pressure wave following it which will draw in air. Quote Link to comment Share on other sites More sharing options...
sussex-landy Posted November 8, 2011 Author Share Posted November 8, 2011 Sounds like an impossible mission to find such a small leak. I will see if the readings have changed now its done a long run then embark on and inch by inch check of the exhaust system, I cant find anything on the air intake or MAF area and the manifolds all look ok and tight. Its strange how its gone so high after the last MOT which it was reading Lambda - 1.029 and its only done 2000 miles over the year. Hate problems like this. thanks robert Quote Link to comment Share on other sites More sharing options...
sussex-landy Posted November 8, 2011 Author Share Posted November 8, 2011 The emmissions were tested again today when it was really hot and it had gone down a bit but not enough so the car had a good check while it was on the ramp and there was no air leaks anywhere. The exhausts were checked and the right bank was running cooler than the left bank and confirmed with a temperature check so the advice was to replace the right bank lambda sensor as its probably a leaner mixture. Does this ring true and it would seem sensible to chane both just for the sake of it. Anyone got any good low cost suppliers of Lambda sensors and do they come out pretty easy, I hate buggering with exhaust bits as I always tend to bust nuts that are well rusted. Quote Link to comment Share on other sites More sharing options...
Pete The Biker Posted November 9, 2011 Share Posted November 9, 2011 I used these people for a lambda for my Subaru Impreza - www.lambdapower.co.uk IIRC £90 for a Bosch part, same as the original unit, instead of £160 for one from a Subaru dealer. Fast service too, and options to take a chance on a 'cheapy' unit without connector plugs, though I would avoid the bottom-end priced ones. Mine unscrewed easily enough (on a 10 year-old exhaust). Pete Quote Link to comment Share on other sites More sharing options...
sussex-landy Posted November 10, 2011 Author Share Posted November 10, 2011 Good info. I have taken both lambdas off the P38 before the cats and have some new ones I am off to pickup, any idea if I can test the old ones somehow. The garage reckons one is running wrong and possibly faulty but will replace both to be safe although at £120 I would like to know the old ones are worse or do need replacing. The car seems to run ok but there again in three years I have had it its run the same and may turn out to be better with the new ones in. Is there any meter setting you can test on a multieter to confirm a lambda is not performing as it should be. ie ohms test when out or voltage tests when running?? Thanks Robert Quote Link to comment Share on other sites More sharing options...
Range Rover Blues Posted November 10, 2011 Share Posted November 10, 2011 I bought some fuelparts ones for my LSE from a local factor, opend the boxs and lo and behold they were NTK parts inside. Quote Link to comment Share on other sites More sharing options...
Ally V8 Posted November 11, 2011 Share Posted November 11, 2011 I would forget the oxy sensors for now,Bosch injected Rover v8's are a bu---ger for low reading Maf's.All the other readings indicate its running closed loop off the oxy sensors.With a low reading Maf the engine ecu cannot provide a wide enough injector pulse to get the oxy sensors to switch up rich.If you can get it on Testbook it should read 22-25Kg/hr at idle,90+ at 3000 rpm,engine hot all loads off. Dont be tempted by cheap replacements from E-Bay etc,I have never seen one that works properly.Either direct from a Bosch agent or genuine LR is the way to go if that proves to be the culprit. Quote Link to comment Share on other sites More sharing options...
SteveRK Posted November 11, 2011 Share Posted November 11, 2011 Connect an analogue AVO style meter to the relevant pins on the ECU, or at the Lambda connector and monitor the sweep pattern between 1 (nominal) & 0 Volts DC. Then refit original Lambda and compare. As a general rule the sweep time from 1 volt to 0 volts is around 1/2 second to 1 second cycle rate. They don't waver or hang around the middle as the ECU is responsible for deliberately trimming fuel from over rich to under rich for various reasons relating to preserving the integrity of the catalyst converters. It may be of course that the heater wire feed to one of the sensors is not working as the Land Rover Lambda type needs pre-heating to work at low exhaust temperatures, or the heater circuit in the sensor is faulty. Quote Link to comment Share on other sites More sharing options...
Ally V8 Posted November 12, 2011 Share Posted November 12, 2011 All looking at the oxy sensor outputs is going to tell you is that they are not switching,not why.And with the emission readings as low as they are there is clearly another fault.Remember the natural output state for the oxy sensors on this car is 0v,so when running closed loop the engine ecu will increase the injector pulse width to give a rich - 0.8v reading.If it cant see this it will just keep widening the pulse width to the limit of the fuel map. Just by coincidence I have one on the ramp at the moment with exactly the same problem,looking at the maf reading its 16kg/hr - far too low.What I have done in the past to show customers what effect it has is to partially block off the airflow into the maf,which speeds the air flow conning the maf into reading higher.when you do this you can then see the fuel trims change and the oxy sensors start to cycle. Ten mins on Testbook will sort out the cause,then its out with the credit card...... Quote Link to comment Share on other sites More sharing options...
sussex-landy Posted December 6, 2011 Author Share Posted December 6, 2011 I got it through the MOT with no other issues but this lambda reading is still puzzling me. I have been running it around a bit and the mpg was better than it is now by 4-6 mpg where I averaged over 25mpg on the motorway and its now around 19mpg so i am guessing the lambda sensors are detecting more oxyygen and riching the mixture up. I am correct in assuming the issue will be before the lambda sensors (which have been replaced) as anything after it would not be sensed and the car would make no adjustments, ie hole in exhaust further down the exhaust path. If this is the case is it safe to assume any exhaust issue is between the manifold and the pipe before the lambda sensor which as it pre cat doesnt leave a lot to check. Does the logic make sense. Cant see any air leaks in the intake system anywhere and considering nothing has changed here and there is less opportunity for corrosion than on the exhaust it seems safe to go back to exhaust issues. thanks Robert Quote Link to comment Share on other sites More sharing options...
sussex-landy Posted January 15, 2012 Author Share Posted January 15, 2012 To continue this thread as i am still not 100% with the vehicle, I have checked everywhere for exhaust leaks and there are none, looks pretty new and shiny for most of it and i would only expect a leak to impact if its before the lambda sensors. MAF has been cleaned up and I am checking with a meter and it looks ok as far as I can tell. I have been told if both lambda sensors are changed something needs resetting on the engine or ECU so the car knows its go new sensors, is this correct has anyone heard of this and does anyone know how its done. Thanks Robert Quote Link to comment Share on other sites More sharing options...
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