My Disco started intermittently running rough & the Check Engine light started flashing.

I got the codes checked at Auto Zone & got: 306, 301, 1300, 300.

I'm assuming that I need to change the spark plug wires & plugs. I see people talking about Magnecor wires - Is it worth waiting & paying the extra for those vs Bosch or Duralast? Opinions welcome.

My Three Amigos lights are also on. I got another code that I assume relates to that: 1590...Neutral position switch circuit high input.

Sorry, I'm a complete newbie - Any input is greatly appreciated.

 

Might be plugs and wires, unless there is major problem with the car causing it to misfire (oi/coolant leaking). The SES light blinks when you have a misfire. Someone more resourceful than me will know more, tho. I didn't have any misfires when I replaced my plugs and wires, but I had probably 8-10 codes, and the magnecores and bosch +4s cleared everything up except for one or two completely unrelated codes. You'll see it posted here time and time again that magnecore are the better choice for your truck, but there are one or two more brands that will work too. I think it's all personal preference, but I sprung for the magnecores. They are about $100 shipped from apex performance.

I have the 1590 on right now, comes on and off intermittently. Its ABS rough road circuit, or something like that. Its related to the three amigos. There's a sticky on how to fix that.

Lastly, I looked up 1300, and my code book said its boost calibration fault. I took that to be related to a turbo charger, but maybe my book is wrong. It is a couple of years old.

 

Thanks for the response - Yes, the SES light was blinking when it mis-fired.

I don't see any obvious coolant/oil leaks, issues that would lead me to believe that there are more serious issues so am I safe to assume that this is a wire/plug issue?

Your definition on the 1300 is interesting - The printout Auto Zone gave me said random misfire.

Any further info related to the above is appreciated.

Thanks all!!

 

Do not buy cheap wires from the parts store, they will not hold up to the heat of the engine compartment.
As hard as the wires are, you don't want to have to replace them again, so yes, buy the 8 mm Magnacor and don't look back. By the way I have a near 10 year old set of them, for what it is worth.

 

When the light blinks, it's not just a misfire, it's a Persistent misfire. The light blinks because you really need to stop the car, as it is the worst type of misfire you can have. Those aren't the full codes, but it could be a persistent misfire in #6 or #1 (I'm guessing from the partial codes). The best thing to do is to have them clear the codes, start the car, press the accelerator for a couple seconds (or just until the light starts flashing), then shut the car off and have the code read again. That way you know exactly which cylinder it is without having to worry about any secondary codes caused by the persistent misfire.

After you have the cylinder number, the simplest thing to do is to pull the plug out, then push it back into wire and place the wire in a safe place (so it won't arc and jump to any metal on the engine). Have someone start the engine and see if you have a spark. Not the way most mechanics would do it, but you can run the car for 30 seconds like that and clear the plug, the wire, and the coil all at the same time (if you do have a spark). If there is no spark, then you know the problem is with either the coil, the wire, or the plug. A lot of mechanics like to use a spark tester, but I like to use the plug itself so I know the plug is also good.

If you do have a spark, then you need to have the cylinder compression tested. You can buy a tester for like $25 and do it yourself, or you can take it to a shop and get it done for about that much. Just note that it only takes a few minutes to do the compression test (like 5mins), but most mechanics don't like to pull a plug when the engine is hot, so they may want the car to cool for like an hour or so before doing the test (I know I like the car to be no more than around 100 degrees when I take a plug out).

The safety switch code could be a general electrical condition. I've seen cars with batteries going bad with a neutral safety switch low voltage code.

In any case, don't keep driving the car if that light keeps blinking. You can cause catastrophic damage to the car. I've never heard of it actually happening, but you can at least theoretically blow yourself up if the problem causes unburnt fuel to enter the cat converter and the converter heats up until the vapor combusts.

 

Another quality wire option is the STi 8mm. bPutah.com sells them for a Very fair price.

 

I use NAPA Belden EDGE 7mm plugs for the Discovery II.

 

Which won't last long do to the heat in your engine compartment.

 

The flashing SES light indicates a catalytic converter damaging misfire. Over the years, I have seen a few cars in need of converter replacement because the owner drove for extended periods with the SES flashing. Raw fuel being dumped into a converter tends to do bad things to them...

Replace the plugs, along with a good set of Magnacor or STI wires, clear the codes, and see what returns.

 

The misfire monitor turns on the light after two drive cycles if misfire exceeds Federal standards test (about 1.875% at 1000 rpm). If misfire is more, and reaches 7.4%, the engine tight comes on immediately. So the concept is that you can have a small misfire, but once you reach about 4 times the minimum level, the truck wants you to do something. Page attached from ECU book that covers this fun fact.