Misfire investigation

[rlaszewski]

I had received misfires and proceeded to purchase Magnecor 8mm wires and Bosch Platinum Plus 4 plugs for my 2000 DISCO II. I have around 80K miles on her thus far.

After doing the replacement, I am getting a misfire on 06 and 07 every once and a while. Other times it runs great without issue. When I do get the misfires, I get the blinking light on the dash and a noticable loss of power..etc..

I have checked and rechecked the plug wire connections and all is well, they are on good and in the correct sequence. I did not take off the Plenum to install the new wires...just bare nucked them in there.

The one thing I did notice was that the plate that holds on the ignition coils is missing the top two bolts that hold it tight to the Plenum. The bottom two bolts are secure, and the plate can't be moved by hand very much. I was wondering if this may be causing the unpredictable misfires if it moves.

I assume that when they did recall work several years ago that required the top of the engine off, that they just never re-installed these bolts.

Other than that, I am wondering where to go next. I have heard about the seafoam treatment, not sure if this would help.

Also, read somewhere about sticky exhaust valves that may cause this issue, and given that sticking isn't something that happens at regular intervals...not sure how to diagnose this problem...an expensive one at that. Any suggestions?

Thanks

[Elemental]

Originally Posted by rlaszewski

I had received misfires and proceeded to purchase Magnecor 8mm wires and Bosch Platinum Plus 4 plugs for my 2000 DISCO II. I have around 80K miles on her thus far.

Why the plus 4s?

After doing the replacement, I am getting a misfire on 06 and 07 every once and a while. Other times it runs great without issue. When I do get the misfires, I get the blinking light on the dash and a noticable loss of power..etc..

Misfire, with Bosch plat plugs.... Shocking.

I have checked and rechecked the plug wire connections and all is well, they are on good and in the correct sequence. I did not take off the Plenum to install the new wires...just bare nucked them in there.

Try installing the correct plugs.

Other than that, I am wondering where to go next. I have heard about the seafoam treatment, not sure if this would help.

It wont. A blinking SES means a misfire so hard it's actually melting the cats.

Also, read somewhere about sticky exhaust valves that may cause this issue, and given that sticking isn't something that happens at regular intervals...not sure how to diagnose this problem...an expensive one at that. Any suggestions?

Thanks

Sticking valves USUALLY will not cause this hard a misfire.


First step I would do would be install the right plugs and stop listening to the kids at the Zone.

[rlaszewski]

The selection of Bosch Platinum Plue 4's was based on the posts I saw in this forum and the positive results I saw, not some dim whit at Autozone.

With the upgraded wires and Plugs...why would there be a problem.

Before the Magnecor wires I had tried a set of replacement wires (STS) and went to normal plugs and was still getting the 06 and 07 misfires...so at this time I ruled out the plug type as the major issue, and decided to go for the best wires and plugs and see what I got.

[Elemental]

You went for the best wires, the plugs are substandard at best. You cannot do a proper diag untill you set a baseline.

[rlaszewski]

baseline being standard plugs with the new wires.

If I run that combo and still get the codes, where to go then?

I will switch them out and see how it goes with the 8mm magnecor and std plugs, but not too hopeful that will resolve the problem.

Hope I am wrong here.

[Elemental]

A misfire happens because one the five things needed for combustion is missing.

You need air..... Likely thats ok because the other 6 are not misfiring.

You need fuel, along with the right amount and pressure. Too much fuel is just as bad as not enough.

You need spark..... Rover spent plenty figuring out what works best in their engines, so, use that.

You need timing.... This too is likely OK as the other cyinders are firing.

And you need compression.

All of which is testable.

If it just comes out of no-where and goes away jsut as easy, I would look at yoru injectors.

[rlaszewski]

Thanks for the advice. I will get to work on it and see how it goes.

[rlaszewski]

DISCO Mike wrote:

Saw your post this morning, also saw that this problem was happening with another set of plugs and wires also, of course none of the critics wiil pay any attention to that, cause they are all firmly believing it is the Plus 4's. This should be an interesting session today. Do you have any of your old plugs, if so, just to silience some of the Bosch critics I would install them in 6 and 7. What octane gas are you running, have you tried to decarbon the engine? How noticiable is the misfire? Mike

[rlaszewski]

I do have the old plugs...not really old, but non-platinum. I can install these on 6 and 7 and see how it goes.

I have run the highest octane since I got the truck, and am the only owner.

As far as Decarb, no I have not done that yet. Wasn't sure best way to do so, all I have heard about is the Seafoam product. Not sure what I need to do with it.

When a misfire does happen, pretty severe. Blinking light on dash, loss of power, shakes real bad, and feels like its going to stall or blow. I back it way..way down and the problem goes away as quickly as it started. Light stays on, but does not blink. when i pull the codes, I get the 06 and 07 misfires. Happens at different times and under different conditions, so hard to predict when it may happen again.

[Elemental]

When your check engine light is blinking, your cat is melting.... No snake oil is going to help that.

Octane has nothing to do with this.....

You have a part malfunction.....

[rlaszewski]

Cat is melting? What is the "cat"...forgive my ignorance.

What part are we talking about?

[Elemental]

The catalyst convertor is too hot from being overfueled.

If the light is blinking, YOU ARE DAMAGING YOUR CAR!!!!!

[AlaskaBound]

Originally Posted by rlaszewski

Cat is melting? What is the "cat"...forgive my ignorance.

What part are we talking about?

The "cat" is the catalytic converter... It looks like a box on your exhaust pipe between your exhaust manifold and your muffler (you have two of em)... It's basically a device that breaks down toxic combustion by-products into less toxic gases before they are omitted out your tail pipe into the atmosphere. Kind of like a carbon filter... Anyway, if you're running "rich" or over fueling, the filters in the cats will get clogged and they can heat up and be damaged... If you're lights blinking, this is most likely what's happening...

[rlaszewski]

With the rich fuel mixture, shouldn't I get a code from the O2 sensors prior to this serious light blinking? My wife's volvo would give me "Mixture too rich" codes which pointed me to replacing the O2 sensors.

I have yet to ever change the O2 sensors on my DISCO II, and am at around 80K miles, so could this be the problem? if the O2 sensors are going and not detecting the rich condition until too late?

[Disco Mike]

Have you gone and had your codes rad aain to see if there are any faults fo O2 problems or the cats.
80,000 mile your O2 sensors should be OK still.
Mike