Homer Posted August 19, 2014 Share Posted August 19, 2014 I've been trying to solve the overfuel issue I have with my UK engined facelift car. I can't so far find any electrical issue, so had a thought today it may be related to the lambda sensor. I remember a long time ago something about the UK being different and having a 2nd sensor in the 2nd cat pipe, is that correct? The car has been de-catted but the end decat does not have the 2nd lambda fitted. Cold this be the reason for the overfuel? Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted August 19, 2014 Share Posted August 19, 2014 As far as Im aware the 2nd probe was a cat overheat sensor and nothing to do with fuelling. Quote Link to comment Share on other sites More sharing options...
Homer Posted August 19, 2014 Author Share Posted August 19, 2014 As far as Im aware the 2nd probe was a cat overheat sensor and nothing to do with fuelling. Could be I'm getting confused then. I know all supras have the cat heat sensor, but for some reason I've got it into my head the UK's had 2 lambda's. Think I'll go get the manuals and see if there's details of the UK spec... Quote Link to comment Share on other sites More sharing options...
Ric Posted August 19, 2014 Share Posted August 19, 2014 The jspec has a Lambda and a Cat sensor, im pretty sure the UK has 2 Lambda sensors and a cat temp sensor? From the GB back in the day, the UK was listed as needing 2 Lambda sensors and Jspec 1 Quote Link to comment Share on other sites More sharing options...
Homer Posted August 19, 2014 Author Share Posted August 19, 2014 Thanks Ric, I also just found the right info in the manual, it does have 2 lambda sensors. Hope this is why may car is over-fuelling, but I have reservations as I can't believe the 2nd sensor has such a huge input to the readings, I'd expect it to be used for fine tuning. Quote Link to comment Share on other sites More sharing options...
Marcus GTE Posted August 19, 2014 Share Posted August 19, 2014 I remember asking about it years ago and it was suggested soaking it in lemon juice rejuvenates it for a while and may help your fuel issue, other than replacing it. Quote Link to comment Share on other sites More sharing options...
CanisLupus Posted August 20, 2014 Share Posted August 20, 2014 Second sensor is just for testing the cats health. If you have an overfuelling issue it could be the first lambda. Quote Link to comment Share on other sites More sharing options...
Lee P Posted August 20, 2014 Share Posted August 20, 2014 Second sensor is just for testing the cats health. If you have an overfuelling issue it could be the first lambda. No on UK Spec, they have second lambda in the mid pipe Quote Link to comment Share on other sites More sharing options...
Burna Posted August 20, 2014 Share Posted August 20, 2014 Lee P beat me to it Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted August 20, 2014 Share Posted August 20, 2014 A lot of modern cars have a second lambda sensor, but its usually just there to monitor the cat condition and doesn't have any impact on fueling, for instance the 350Z has this setup, i removed the cat monitor O2 sensor and it had no impact on fueling, so i doubt its related. Quote Link to comment Share on other sites More sharing options...
CanisLupus Posted August 20, 2014 Share Posted August 20, 2014 No on UK Spec, they have second lambda in the mid pipe Then what could it do the after the cat? It is a lambda sensor and after the cat it can not be fueling related... Quote Link to comment Share on other sites More sharing options...
Homer Posted August 21, 2014 Author Share Posted August 21, 2014 A lot of modern cars have a second lambda sensor, but its usually just there to monitor the cat condition and doesn't have any impact on fueling, for instance the 350Z has this setup, i removed the cat monitor O2 sensor and it had no impact on fueling, so i doubt its related. This makes perfect sense mate and sort of what I had in my non-technical mind. I'll cross the 2nd lambda off the list of problems. Back to the drawing board but thanks to all for the input Quote Link to comment Share on other sites More sharing options...
Big Supes Posted August 21, 2014 Share Posted August 21, 2014 I'm in the process of addressing this issue on my uk car. Have you tested the voltage via the engine diagnostics? Mine reading was 0.3v which would confuse the ecu into thinking the car was running lean. I've got a new lambda sensor and will be fitting it the weekend. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted August 23, 2014 Share Posted August 23, 2014 Any garage with a `scope can look at the waveform update time and volatge from both sensors, at the diagnostic socket, in ten minutes. They can then see what happens on idle, fast idle, and throttle snap. Any other testing is pretty meaningless with O2 sensors. More modern engines and control systems allow a diagnostic reader to see all this in real time, with short and long term fuel trims visible, and a huge amount of other real time data, but the MKIV is far too old to do all that. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted August 23, 2014 Share Posted August 23, 2014 I'm in the process of addressing this issue on my uk car. Have you tested the voltage via the engine diagnostics? Mine reading was 0.3v which would confuse the ecu into thinking the car was running lean. I've got a new lambda sensor and will be fitting it the weekend. As its a cat function O2 sensor the ECU will be set to respond with a CEL should the output voltage be out of range, and as a cat will cause the O2 voltage to show as lean when doing its job properly, it will only trigger a CEL when the sensor shows a rich reading, so a 0.3 volt reading would be about correct IE lean. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted August 23, 2014 Share Posted August 23, 2014 The MKIV ECU is very crude compared to the latest stuff. If you think about it, a UK car would show a fault code with both cats removed, as you would expect the second O2 sensor to see a too rich a mixture. But they do not flag a code, so they must be doing something else. Quite what or not I am not sure. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted August 23, 2014 Share Posted August 23, 2014 I'm surprised Chris, i would have thought that it should throw a code if it was rich, in the same way that the J spec would throw a code if the cat temp sensor is left in when decatting and it sees too high a temp..strange, will have to have a good squint at the manual and see how the second O2 is wired in the ECU. Quote Link to comment Share on other sites More sharing options...
Big Supes Posted August 23, 2014 Share Posted August 23, 2014 As its a cat function O2 sensor the ECU will be set to respond with a CEL should the output voltage be out of range, and as a cat will cause the O2 voltage to show as lean when doing its job properly, it will only trigger a CEL when the sensor shows a rich reading, so a 0.3 volt reading would be about correct IE lean. I see... my car is running rich and sometimes stalls if I blip the throttle and shut it. Originally I thought it was idle air control valve, but the running rich has me thinking the O2 sensor is kaput. Another possibility is a boost leak as it will no longer pull more than 1 bar of boost (running full bpu), but I have been over all the boost pipes and they all seem ok. Quote Link to comment Share on other sites More sharing options...
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