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Range Rover 4.6 1997 - Rich running - Fixed #

Posted by Blair Rosson on May 18, 2011, 12:10 am

Year of Manufacture *: 1997
Engine Size and Code *: 4.6 46d
( Optional ) ECU Type: gems
( Optional ) Scanner Used: dec

Vehicle came in for rough running and the fuel short fuel trims were sitting on +25 long term was -30.5.
i have measured the voltages at the ecu for the oxy sensor (titania type) and the voltage was 4.97 (appears to be lean output), i pulled the sensors out and tried all sorts to make the voltage decrease to mimik a rich mixture but they didnt move at all,
i have fitted 2 replacement sensors (NTK)
now both are reading 0.05 volts (rich) i can remove the vacuum hose to let more air in, the sensors start moving and cycling as per normal, the fuel pressure is only 30psi and goes to 38 with pressure regulator hose disconnected.

questions are my sensor supplier says that 0volts is lean and 5v is rich? this contradicts what i have found as removing the new sensor from exhaust and still plugged in i have 3.8v and rising which indicates lean,
who is correct here?

how can i reset fuel trims?
what can you point to to lean it off?
coolant sensor appears correct with operating temp, fuel temp sits around 38deg.

any pointers for me

Re: range rover rich running

Posted by Mark Robins <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1448' width='330' height='300' border=0 style='border:none;'> on May 18, 2011, 8:36 am, in reply to "range rover rich running"
Mark Robins

If it's a fuel adaption issue a good run will usally reset it, coolant temp seems on the low side usually needs to get above 60 to go closed loop, have you got a thermostat problem?

Mark
P.S.
I've e-mailed you a spec sheet on O2 sensors.

Re: range rover rich running

Posted by Blair Rosson on May 18, 2011, 10:06 pm, in reply to "Re: range rover rich running"
Message modified by board administrator May 19, 2011, 2:56 pm

Hi Mark,
thanks for the info, i think i should clarify that the engine coolant temp was good, it stayed above 89deg even with a 20km drive. the fuel temp was only at 38deg.

the thing is the trims are now both -25 on short trim and still -30.5 on long trim, so basically its gone from one extreme to the other,
i feel i have an issue that has caused both my oxy sensors to fail giving me the +25 fuel trim that i initially had, now i have replaced them the true fuel mixture is showing and its rich, only a slight air leak and the sensor start to move. my injector pulse at idle with the trims they are now is 2.65ms.
finding another range rover here in NZ is not impossible but not easy to find to compare or even pinch an AFM to try.
do these vehicles give these issues??

Re: range rover rich running

Posted by Mark Robins <iframe src='https://members5.boardhost.com/ukautotalk4/info/user=UKAT1448' width='330' height='300' border=0 style='border:none;'> on May 18, 2011, 10:57 pm, in reply to "Re: range rover rich running"

Hi Blair,

I haven't got a great amount of experience on Range Rovers, but your injection durations are not a million miles out possibly still indicating a adaption issue, AMM problems in my experience usually tend to give lean readings can you scope it? Normally you are looking for peak voltage around 4 to 4.5volts range. Also look carefully for any exhaust leaks up-stream of the lambda sensors, faulty injectors or maybe even a faulty ECU I have come across on other vehicles with this type of problem. Can you look at plug condition to maybe indicate a rogue over fuelling injector?

Fixed #

Posted by Blair Rosson on May 31, 2011, 10:32 am, in reply to "Range Rover 4.6 1997 - Rich running #"
Message modified by board administrator June 1, 2011, 7:23 pm

Fitted a secondhand airflow meter as per customer requests, road tested and fuel trims came back to a 'normal' operation

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