Discovery 2 V8 2001 - Engine Running Issues

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Originally Posted by ballbag

Sounds like spark rather than fuel to me. Why would fuel pressure drop after ‘idling for a few minutes’?

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The OP says "Stops after idling for few minutes misfires under load at and over 3500 rpm", This is atypical of a fuel starvation issues, Blocked filter, contaminated fuel or faulty pump.

This problem I quite common when fuelling from jerry cans or from some other source of contaminated fuel which blocks or partially blocks the fuel filter and makes the fuel pump work "overtime".
Unfortunately the filter and fuel pump on a D2 are inside the fuel tank instead of being external so it is much more difficult to check this But it isn't an insanely difficult or expensive job to do.
I would be eliminating this possibility Before spending money, time and knuckle skin on replacing coil packs

Misfire under load and at revs correlates with fueling issue, but I’ve never known an engine to stop idling after a few minutes because of one. ‘After a few minutes’ to me says heat related, therefore electrical, therefore spark. Or perhaps fuel pump relay or indeed the pump itself.

Whatever the case, fun times ahead! [emoji481]

There's always the stuffed fuse box scenario, look for fried circuit board around any of the relays, especially the fuel pump relay.

do we have any pics of said circuit board?

cut out after warming up/idling could be the CAS giving you warning,, they do do that before outright failure.

You could have worn a couple of lobes off your camshaft. Comon problem with RV8s......

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Originally Posted by John R

Dear Forum members

I have a 2001 Discovery 2 4.0 V8 with Thor Engine. The car drives beautifully normally but recently it's displaying various symptoms to indicate something is wrong. These symptoms are:-

Stops after idling for few minutes
misfires under load at and over 3500 rpm

I have purchased a iCarsoft LR V 1.0 OBD reader and the only code error it gave me was that there is an issue with the MAF sensor.

However other threads indicate possibly failing ignition coils and or even problems with the HT leads to the plugs.

Noting that the car has ben serviced regularly, has 200K on the clock and uses almost no oil and has new spark plugs. Can anybody help me with a possible diagnosis (or similar experience) before I start on a process of elimination by changing a whole bunch of parts.

Regards

John R

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indeed it could be problem with the MAF senzor, and the easiest way to try it with an another one. But if you have diag, you can probably check the amount of air at iddle it should be around 20 kg/min. under no load, it means switch off aircon, etc. also check the long trim adaptation, and lambdas. it could be a good indicator of issue, if there is a relative big deviation, it could point to MAF ( if the deviation is the same for both lambdas) or lambda ...
in case of no result , you can follow to check other possible issues

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Originally Posted by bee utey

There's always the stuffed fuse box scenario, look for fried circuit board around any of the relays, especially the fuel pump relay.

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Hey folks

I've run this to ground by changing the 2 x O2 sensors pre catalytic converters - which were totally not OK. Got rid of the poor running and missing - the engine is running much smoother now. Also I am replacing the MAF as it appears to be a contributor with poor idle and possibly too rich a mixture. Out of interest the long term fuel mix was sitting at around 22% for both banks and the O2 waveform was not a nice square wave. the MAF reads "circuit low" (words to that effect). Im now waiting for the replacement MAF to arrive and see how that settles the motor. The lambda on both banks is now at a steady 1:1 so fingers crossed Ive sorted the issue. Thanks for all of your help and suggestions so far.

1.1 is not good,,
.1 to .9 is ok,,
and they vary,, constantly

and I THINK,, 1.1 is the rich end, so your maf is still stuffed!![bigrolf]

Does the ECM not go into some default, open-loop fuel map if O2 values are outside the realms of acceptable?

I would expect it would revert to a rich mix for safety and that it would run without misfiring.

I guess not?

I towed the van for a while [bigwhistle] with the LTFT at +22, and it ran ok, I think it tops out at 25?
and no,, I havent read anywhere of a failsafe setting,,

V8 owners need to understand the car is completely at the mercy of O2 sensors.