Discovery 2.0 MPI emission failure

Hello everyone, I'm back with my 2.0L MPI Disco!

Of course with issues. Recently went in for an M.O.T test and failed on emissions (high CO)
I checked all the vacuum hoses, all were okay, So I replaced the Oxygen Sensor, the engine seemed to run a bit smoother, so I took it back for it's M.O.T and it failed again on emissions.

So I plugged in my pscan.eu and found that the engine never went into closed loop. So I swapped the ECU with a spare and Hey Presto it did go into closed loop, however it ran very poorly compared to the other ECU.

So I think that both ECU's may be faulty and I require a new one, anyone got any other ideas?

IIRC it has a MAP sensor? if yes that's suspect

It has an air temperature sensor instead of a MAP sensor which I have changed recently.

Can you r4ad live data with your scanner as to see the fuel temp, calculated manifold pressure, etc? ...are those readings OK?

Fuel temperature seemed okay, but the calculated manifold pressure was 38-39 Kpa, I'm not really sure if that's right or not. But according to google should be between 54-67 Kpa. Which would suggest quite a vacuum leak.

And the inlet air temp reading is OK?, you can check that first time in the morning immediately after a cold start cos then the IAT should be very close to the ambient temperature also the rpm reading is OK? ... this rover engine has a very strange management cos most of the data is calculated based on rpm and throttle inputs, that manifold pressure doesnt seem OK to me... based on logic cos i dont have much experience with this engine the MAP should be very close to the ambient pressure at idle and to grow with revs

maybe you should rule out that ECU first with a 100% well working one though...then go further

Thanks Sierrafery, I shall check those when I get the chance.

Your Map pressure at idle is in the parish, it will only go to 100Kpa at wide open throttle.(When there is no manifold depression)Swapping ECU's around is not a good idea without Testbook as these units had setup procedures that need to be followed through via the Testbook menu. When done properly they will match the ECU properly to the engine and make it run well.Sorry I can't give more detail,but its a long time since I had one of these in for diag.

I dont want to contradict you cos i really dont know much about the 2.0 mpi engine but i'm curious how it's possible to have lower MAP than the ambient pressure at idle? ... this engine doesnt have free flow from the intake to the inlet?

No problem, the ecu on these uses manifold absolute pressure to calculate airflow, unlike the conventional airflow meter on a TD5 etc. So the Map sensor is placed in the inlet manifold after the throttle butterfly. So at idle you have the highest manifold depression or most vacuum. Only with the butterfly wide open will you see atmospheric pressure or very close to it,as its just air rushing along a pipe.

AAAha.... got it, i've learned something today, thanks