I jave a 1997 Discovery XD (about 83k miles) recently running very rough idle. The truck couldn't maintain idle after start and I have to keep stepping on the gas padle a bit in order to keep it running, and often got the engine died at the tracffic light. Rear Eaxaust has a bit black smoke.
Can anyone guide me where to start to get this problem solved? Many thanks!

 

Some updates. So I disconnected the battery cables and let it sit overnight. This morning I reconnected and started the truck. It seemed OK at the first crank, idling at around 800rpm with no stall or hesitation. I checked the code but got one P1172. Was it telling me a MAF failure or O2 sensor failure? The red Service Engine light is still on.
Thanks!

 

So some more updates, I turned off the Service Engine light by finding the 83K Emission Maintenance Reminder switch, and resting it using a metal pin. I also rest the code using the ODSII handset, and retest the behicle, got no code this time. The truck seemed running OK now with a stable idle at around 750rpm. Not sure it will be bumping running again, will see.
I also check the MAF sensor, it has 3-pin connector, the red wire feeds 12v to the sensor, and the brown/green one was the ground. the middle blue output the MAF signal, using a digital multimeter can take it's output..