2004 Land Rover Discovery II 122k miles

The Land rover has a rough idle. Trying to eliminate that tomorrow with new plugs and wires. Any other suggestions? Coil pack? Just strange that its throwing so many misfire codes. Tried finding a similar forum with no luck. This is my first post. Thanks
P1300
P0305
P0307
P0302
P0300
P0305
P0307
P0302
P0303

 

Some of those codes are repeats. What cylinders are not misfiring?

Here's the coil diagram:




With so many misfires at once I'd guess you either have a massive vacuum leak or a bad MAF. But that's just a guess... What's the recent history and what happened that you started replacing parts?

 

Cylinder 1, 4, 6, 8

 

Geez. That's alot. I still stick with my guess of a large vacuum leak that you should be able to find by spraying brake cleaner around the intake and vacuum fittings or it is the MAF.

What's the truck history? Or what happened right before all of this started?

 

Well I just recently purchased it. Didn't have a check engine light. Has a slight rough idle but nothing major so I figured new plugs and wires would take care of that. Guess we will see tomorrow. It just got worse and worse over time with rough idling. If you gas it, it straighten out. Doesn't seem to have a problem accelerating either. Only while idling. Brand new air filter, new cooling system. Tomorrow I'm having a new thermostat installed, spark plugs and wires, oil changed, coolant flush, greasing u joints and drive shaft. (U joints were already replaced luckily)

 

I've had misfires from the following causes:

Vacuum leaks in lines or plenum gasket
Bad injector
Bad spark plug
Bad coil
Wires to wrong place on the coil
Disconnected connector (everywhere... But check the gray one on the top, back, driver side of the upper intake first).
Head gasket
Bad MAF. If the MAF was disconnected you would get a code for that.

I am sure there are other causes but since you have four misfires and if everything was working well before it has to be something that affects all of those cylinders. That rules out head gasket and injector. Probably rules out spark plugs because they wouldn't all go bad at once. Coils are possible but the most likely is a vacuum leak or bad MAF... At least that's what I would focus on first.

 

Can the MAF be cleaned? Or is it something that needs to be bought new? You're right about so many spark plugs going back at once..doesn't seem right

 

yes the MAF can be cleaned. Just do it when it is cold and dry thoroughly. Three of the misfires are on 1 coil, New coils took care of mine.

 

you might want to clear those codes and see what comes back.
but plug and wires never hurt

 

Update: Sorry it took me so long to reply..The land rover had a compression test today and the results came back okay... told me that it needs both coils and upper intake gasket. I attached a picture of the old spark plugs..not sure how many miles are on them but know at least 30k