I was a few miles from home one day when my 2000 Discovery suddenly lost power and was barely able to limp home. I thought it was a blown coil pack but now I'm not sure since it appears to be running on cylinders 1,2,3,and 4, which shouldn't be the case due to the firing order. It occasionally backfires into the intake but not very hard.

The motor has about 35000 miles on it.

I was traveling at a normal speed when this happened, and it made a faint sort of whisp noise (like a sudden and quick release of pressure, or the noise you would hear if you stepped on a ketchup packet) at the instant that it lost power.

I hate to think it could be a broken camshaft, please tell me I shouldn't even think that.

What are all the possibilities?

 

If the cam were broken it would not run at all.

Check your coolant level and then get back to us.

 

Coolant level is good,

Service engine light flashing,
sulfur smelling exhaust,
OBDII codes thrown as follows:
P1300 Catalyst damaging level of misfire on more than one cylinder
P0154 o2 no circuit activity detected (bank 2 sensor 1)
P0308 cylinder 8 misfire
P0306 cylinder 6 misfire
P0305 cylinder 5 misfire
P0307 cylinder 7 misfire
P0302 cylinder 2 misfire
P0134 o2 no circuit activity detected (bank 1 sensor 1)
P0300 random misfire detected
And again with
P0308
P0306
P0305
P0307

 

the exhaust manifolds are hot at 1,2,3, and 4, but cool at the other cylinders

 

Ok, that means that only 1,2,3,4 and firing and not the other 4.

Could be a bad coil, I think that all of those cylinders are on the same side of the coil packs.
Josh has a diagram of the coil and plug routing.
People have reported having bad/dirty connections where the coil packs plug into, so you would need to remove them and look at the connections.
But lets start here.
Pull out one of the non working plugs, reattach the plug wire and start the truck, does that plug spark?

 

So both your primary 02's are not working, that will throw the whole system. How many miles on the 02's? If near 100,000 miles then replace all four of them first, then clear the codes and see what happens.

 

All cylinders have a good fat spark

 

Then go with what Mike suggested. what is your mileage? Have you replaced your O2's?

 

As I understand O2's, their readings don't affect anything until the engine is warm. So I cleared the codes and started it, but it still runs the same way. Since it takes a while for the readings to matter as the engine warms, it should have run normal until an O2 could have thrown it off. Am I correct?

I think the O2's have 117,000 miles on them, I bought the car with 75,000 on it with a brand new engine from Land Rover (warranty replacement). Would the O2's throw off timing and fuel to 4 cylinders and not the other 4?

It seems strange that the front half of the engine runs, but the back half doesn't, even though the firing order and coil packs don't separate it that way. Wouldn't a problem with o2's throw off everything equally to all cylinders and not just the front half? I just don't want to spend a bunch of money that goes to new parts but doesn't fix the problem. Is there a reliable way to test O2's before I buy new ones?

 

Hook it up to a computer like testbook or a T4 scanner to check the readings. That is how you can test them. They are reaching the threshold for normal life and should be replaced either way.