UPDATE- Just back from a test drive- smooth sailing, better than ever. What a relief after the dramatic, ominous, misfiring engine. Solution was new plugs and new plug wires. Thanks for the sticky on how to change plug wires without removing manifold- worked like a charm. The following is what I originally posted which may help if you experience similar codes:

Hi All,

(Before I begin, please note that I did try search, could find many threads on codes, but hard to find the resolution- I see that many roads lead to Disco Mike, however.)

My Disco is a late 2003, has 112K miles now, and has been a real joy in the past few months I've owned it. However, I'm so used to old cars and trucks, that I don't know how to handle it when flashing lights start blinking at me. (My auxilary back up Land Rover is a 74 RHD Series III- no codes on that one)

I've noticed over the past couple weeks a little miss, kind of a random thump, at idle. Other than that, it ran just fine. Then last night on the interstate, it started missing significantly, then the service engine soon light started flashing. The miss seemed to fade in and out, worse under power.

This morning I checked for codes and found:
300 random misfire
301 cylinder 1 misfire
306 cylinder 6 misfire
P1300 catalyst damaging misfire multiple cylinders

I pulled spark plugs 1 and 6. 1 looked fine, 6 looked wet as if not firing. I put in two new plugs, but symptoms seem about the same. I ran codes again, just 306 this time. At idle, there is a noticeable miss, but as it revs up, seems to get better, then get worse, depending on RPM. There are bands of RPM where the miss is very noticeable, then mysteriously gets better at different RPM.

Couple other things: coolant level and oil level seem perfect, no overheating, and this sure seems like more than one cylinder missing when it is at its worst! And it doesn't do that steady miss like the old stuff I mess with- this is real variable.

I don't know how old the plug wires might be- seems the next step to me, but I'd like to have your ideas before just throwing parts at it.

Can you tell me the next step toward solving this mystery?

Thanks! Jeff

 

I just wanted to make sure anyone with similar codes can also find the results.

I had 300, 301, 306, and 1300 codes, variable misses in the engine from slight to all the way to "wonder if I'll make it home".

New plugs and spark plug wires, all 8 cylinders, and it is now smooth as silk. I was able to put the wires on using the information from the "sticky", didn't pull the intake manifold. A BIG THANK YOU FOR THE GUIDANCE HERE!

Drove 160 miles today- back to lovin' my LR.

Jeff

 

Sweet.

 

My service engine light has been on, and I had someone check it. These codes came on.
PO300
PO301
PO1319
P1300
PO442
PO302

Is this going to cost me a fortune?!

 

You might want to start your own thread vs bumping a 2yr old one.

 

Did I respond to this? This is the same thing that happened to me. My codes were.

PO300
PO301
PO1319
P1300
PO442
PO302

Do I need to take it to the dealer? 102,000 miles and I have a long drive on Saturday. I'm not mechanically like you are.

thanks!

 

We completed the plugs and wire over a weekend using the RAVE manual directions. There was no humanly way my hands were going to fit behind the upper inlet manifold. SAI system is the biggest headache in the whole process.

The cost for a dealer was quoted at $1,200 for the previous owner and our independent I believe would have charged $800. We did the work ourselves and kept the difference.

A note on the dealer, they will use only their wires and plugs and other members on this board recommend MAGNECOR or STI wires. Do not start a a recommended plug thread as there as a many opinions on plugs as there are grains of sand.

If you are leaving on Saturday, I would recommend using the Car Talk guys web site for finding a good local mechanic ASAP if you do not already have a trusted mechanic.

2003 Discovery 128K with high miles service complete.

 

P0300 Random/multiple cylinder excess emissions detected
Excess emissions detected on more than one cylinder

A code P0300 may mean that one or more of the following has happened:
* Faulty spark plugs <http://www.obd-codes.com/p0300#> or wires
* Faulty coil (pack)
* Faulty oxygen sensor(s)
* Faulty fuel injector(s)
* Burned exhaust valve
* Faulty catalytic converter(s)
* Stuck/blocked EGR valve / passages
* Faulty camshaft position sensor
* Defective computer

P0300 Misfire On Multiple Cylinder
P0301 Misfire Cylinder 1
P03O2 Misfire Cylinder 2


P1300 catalyst damaging misfire multiple cylinders
PO442 - EVAP EMISSION CONTROL SYSTEM LEAK (SMALL)

I drove yesterday and car feels and sounds great. Even the familiar knocking noise isn't there. Landrover Manhattan will charge a fortune to fix, and my local mechanic says it sounds like it needs a tune-up. If no wires needed $450 approx. 700plus if needs wires. Does this sound about right?

I'm going to drive it Saturday as is, as I need to drive and cannot leave it over the weekend.

Please advise if anyone has suggestions. Also cannot find one code PO1319.

THANKS!

 

New Land Rover Owner, Converted from FORD!

I just got a flashing check engine light yesterday, i checked everything out and the truck had burned nearly all of her oil! so i did an oil change but now she's misfiring in Cyl 1 & 6 ramdomly. EXACT SAME CODES AS IN Original post!!! I am taking her to a shop to get looked at but Could it be something as simple as the plugs and wires? how much should I plan on paying?

 

Sure it could be! Are your wires original? Plugs? Could be a coil pack, could be as simple as a loose connection.

What should you plan on paying? Good question all shops vary on there hourly rates.