Random / Multiple Cylinder Misfire Detected

[jaxy]

I am from NY, my 05 Lr3 due to pandemic has been mostly sitting in front of my house since March 2020. In summer I used to start is once in two or three weeks. Come winter I started doing it more often, like twice a week and did so even after each snow storm.

After last snow storm cleanup when I started it and felt it was shaking and running rough. Engine light came on as well, so over the weekend I checked and got the following codes.

P0300 - Random / Multiple Cylinder Misfire Detected
P0301 - Cyl 1 Misfire
P0306 - Cyl 6 Misfire
P0307 - Cyl 7 Misfire

Also due to sitting battery goes low, as I see the message or HDC fault on starting and it goes away after a while.

My question is
- Could these codes be due to low battery voltage/current (Battery is around 3 years old)
or
- Could be clogged spark plugs due to sitting for long?

Your help is as always greatly appreciated.

 

[Houm_WA]

Since it was running rough I'd say that the codes are not voltage-related, but the HDC fault is. I'd be trickle-charging that battery and do more than just start it every few weeks....drive it! ....it may benefit from a BG fuel treatment at this point.

 

[jaxy]

Pardon my ignorance so I do nothing for plugs or coils. Just put BG fuel treatment, trickle charge battery and drive it. Correct?

 

[Houm_WA]

Sure, for starters. Since it's been sitting around it could just be contaminated fuel. There is a BG treatment that goes through the air induction too. I would try that one and the gas tank one, together. There is also a can for the fuel rail.

 

[justingreene]

I had a similar issue on my 05 LR3. Using mode 6 on BlueDriver I found that I had a single coil that was showing errors even though I was seeing misfires on others. When I replaced that, the other misfires went away. However a few months later I started having a number of misfire issues and O2 issues and eventually ended up replacing 4 more coils which resolved everything. It made sense that the coil replacements would solve the misfiring but I though it peculiar that it would solve the 02 issues.

Separately I have had HDC issues that went away with a battery replacement. I am also in NY and have had to replace the battery every 3-5 years.

 

[bbyer]

Coils - yes, my Independent replaced a couple on my 4.4L V8 a few months back.

I had noticed a bit of stumbling so to speak so decided it was about time to replace the spark plugs. I do that about every 50 thousand miles, not so much because there is a plug problem, but just to make certain the plugs have not had a chance to "weld" themselves into the aluminum head.

As such, when my Independent casually mentioned that they replaced a couple of "coils", I immediately assumed Helicoils and got all excited.

Bottom line was new plugs, the two new coils and all good.

In the case of the thread related questions, I expect you have a combination of everything; the main problem being lack of use.

Tractors seem to be able to sit around most of the time and when finally started up, all good. Land Rovers are not the same.

Yes to the trickle charger when sitting. I expect you have some weak ignition coils so the combination of that and a low battery yields engine problems. Do not expect the alternator to charge the battery back to where it is anywhere near even an 80% state of charge - only a battery maintainer and time will do that.

As to the fuel, the BG stuff, may help as well. I did that a few months back and cannot claim anything good or bad but if the BG helps to clean the pipes up, so much the better.

My 3 is a daily driver, hence the fuel probably is far from stale. Each early winter, I pour in some gas line antifreeze so there is probably not much water in the tank as the gas line antifreeze combines with water. The net result is any water exits the tank via the muffler. For the warm climate types, probably the water content in the tank just keeps building up over the years.

 

[mgkonopka]

I had the same issues with my 08 right around 85k. Misfire - replaced a coil. Repeat two more times and I just decided to replace them all. Went ahead and replaced the plugs as well. Sitting at almost 130k and haven’t had any other misfires.
When my alternator went south it started with a hard to start fault then no start. I replaced the battery and this helped but still got all sorts of error codes and dashboard lights. When I finally succumbed and took it in they said it was the alternator. The mechanic told me when a Land Rover has an electrical fault it will throw codes that aren’t related to what is actually going on. You have to clear the faults, run the car and see which codes appear first to see the cause.

 

[bbyer]

The mechanic told me when a Land Rover has an electrical fault it will throw codes that aren’t related to what is actually going on. You have to clear the faults, run the car and see which codes appear first to see the cause.

You have a good mechanic there. The problem with the who fault code game is the computers can only feed back what they have been taught.

One thing none of the computers are every taught is "faulty electrical connector" or "broken/breaking/corroded wire". As such when that is the problem, the computer makes a series of near guesses. This is where, like a doctor, you hear the patient describe the problem and then use your experience to determine what the problem really is.

I have found that these alternator problems are rarely cooked diodes or bad windings or whatever commonly goes wrong in a GM alternator, but instead it is the "smart" regulator within.

Well that is what Ford calls it, but actually it is really dumb.

Once upon a time, the regulator was a black box bolted to the firewall. Then someone (probably ex NASA) figured out that the back box could be inserted within the alternator and a bunch of wires would be saved as the regulator within could do all the black box could.

Then another smart guy who I guess designs car computers decided that the regulator could be built into the car computer. Doing so meant that the there could be fewer transistors within the alternator - all that was needed was something that told the field windings to tell the big winding to make more or less amps.

Since Dumb Regulator did not market test well, hence it was renamed a Smart Regulator, or for the technical types, a vehicle PCM controlled voltage regulator where PCM means the Car Computer or more precisely, the Powertrain Control Module. The actually signal that the alternator listens for is something called a PWM, Pulse Width Modulated signal that is generated by the PCM - simple eh!

The pdf speaks of AS, External Voltage Sense. This is code for gets the voltage number from somewhere other than the alternator itself. Note the default sense point mode (14.03V). This is code for when the "external sense mode" fails, the alternator produces amps at 14.03 volts, enough to keep the vehicle going but not enough to charge a LR battery.