A misfire is when the mixture of fuel and air inside a cylinder doesn't ignite. Since ignition requires three components -- fuel, oxygen, and spark -- the fault can lie with any one of those areas.

Lack of spark is self-explanatory, and can have any number of different causes. Lack of fuel is similarly self-explanatory, but again can appear for a number of different reasons. Lack of oxygen is rarely a problem; it's usually caused by blockages in the system that brings air into the cylinders.
However, there's a wrinkle in diagnosing problems with both fuel and air, which is that they need to be in the correct proportions to ignite correctly. Just having both of them getting to the cylinders doesn't mean everything is good. In addition, the fuel/air mixture needs to be compressed by the pistons so that it explodes, rather than simply burning. If there are leaks in the cylinder (e.g. there is a breach in the "head gasket" that seals the top of the cylinder, or the valves in the top of the cylinder are not sealing effectively, or coolant is getting into the cylinder due to a leaking head gasket) then the cylinder may not fire.

Usually people will notice misfiring when the Check Engine light comes on, or when the engine starts running roughly when it's idling.


The internet is full of good explanations of the operations of a 4-cycle gasoline engine. You might want to look around and familiarise yourself with some of the basic terminology and systems so that you have a better understanding of some of the responses that people might provide here.

 

At times, when first driving after it has sat overnite, it will idle down as though it wants to cut off but not low enough to cut off (more like a slight 'tremble') while I'm at a red light ...no check or service engine light on....tc and his descent lights have been on about 2 wks though

 

Find yourself a new tank, everyone tries to fix it and it never lasts.
It's not worth losing an engine over.

 

Hopefully that means OP has a new one in hand?
......

 

My bad

 

It was well hidden with long description of failed attempt at temp repair. My reply was a +1 on the replacement suggestion and it being hopeful.
.....

 

Yeah I just picked up another one..any pointers I may need for the switch out?

 

Since I've had my 01 d2. I really never worked on a car that much. with these forums and youtube. I've managed to replace plugs and wires, coil packs, radiator, new water pump, new alternator, fan clutch, took heads off and put in remanufactured ones, plus a few seonsors by my self. Not all at once, but over the course of a couple years.

With the help of these forums, google and youtube. You will be a Rover Master Mechanic in no time.

 

My first car work of any description was when I decided to do the first oil change on my new Disco II because I didn't want to drive all the way to Dallas to get it done. I dumped the transmission fluid thinking that was the oil pan (I was wondering why the oil was red but whatever, I thought, it must be fancy oil) and had to have it towed 200 miles to Dallas. I called the deslership and they said a human being without special tools cannot refill the transmission. By special tools I think they meant a five dollar plastic pump. Last week I changed my engine right in my driveway for the umpteenth time.

The next time I needed service I did take it to Dallas, on the morning of 9/11/01, for an oil change and the first major checkup. It took two weeks to get it back. I haven't been to the dealership since then.

So I moved to a local shop when my transmission acted funny and they replaced it. It cost thousands. I'm sure it under warranty but whatever. A week later I found out I just had a bad battery when the new transmission did the same thing.

Three weeks after I paid the truck off and the warranty expired, my head gasket blew. I let the truck sit in my garage for five full years before figuring that one out, with my new friend, land rover forums.

As time goes on there will be two kinds of Disco owners.... Those who fix their trucks and those who break them. Those who fix them will find cheap parts trucks. The OP is ahead of the curve being here at this juncture.

 

True that. Ive been looking for a good parts disco, but until I do. ive been using ebay for pretty much all of my parts. I want to get a decent parts truck and rebuild which ever one is nicer by turning mine into the parts truck or the other.