So, I'm having an issue with my '05 LR3 4.4. everything has been running great lately, until the other morning when suddenly it developed a rough idle. Check codes and it says random misfire and misfiring on multiple cylinders. Then, while driving home, "Engine System Fault" comes up and check engine light starts to flash. This was accompanied by a loss of engine power. Anyway, got it home, and thought I had it down to a failing alternator... Just finished replacing it tonight, and the problem is still there. Now I'm wondering what else it could possibly be? Possibly an engine ECU going out? Grounds? Any other thoughts on what this could be? No obvious signs of moisture intrusion. MAF is clean, spark plugs are new. Can MAF suddenly fail? Any other points of sudden failure that could cause this? Thanks in advance for any advice you may have to offer!

 

I had similar symptoms during an overlanding trip driving a 2005 LR3. It ended up being a combination of clogged injectors from dust and a failing injector. Keep these questions in mind when troubleshooting: What exact codes were present? Were there any fuel rail pressure codes? what exact cylinders are misfiring? Is there a pattern? Are the miss fires exclusively/mostly one bank? What octane fuel did you last fill up with? Was it a reliable gas station? Did the problem start after refueling? Was the car left for an extended period of time (stale gas?) Is there a certain RPM where it runs "smoother"? If you can read the fuel rail pressure what is the reading?

I'm thinking your issue could be one of the following

1. Failing/leaky/stuck injector(s)
2. Picked up some low quality gas somewhere causing misfires
3. Sparkplugs could be faulty (new doesn't always mean good) This would be applicable if the misfires are usually on 1 cylinder.

Depending on your thoughts on Seafoam, you can try pouring a bottle in your tank to clean the injectors. If you believe you picked up bad gas you can fill the rest of your tank with trusted quality fuel. Not sure exact problem that causes bad gas (hahaha) or best solution. But I've had luck with pouring a bottle of octane booster in there.

When my MAF failed it shut down the engine and would restarted and instantly die. Without any codes.

 

BG 44k might also be an alternative if seafoam doesn’t feel like your cup of tea.

 

These were my first thoughts as well! I added a can of BG44K and topped off the tank. So far, it doesn't seem to have helped any, but I only drove it about 15 more minutes before arriving home. The GAP tool first reported a misfire in cylinder 8, but after driving home it reported misfires on multiple cylinders (like 6). Is it safe to just let it idle for a while to let the GAP tool get more information?

 

Could be ignition coils as well. A buddy of mine had the same thing going on, changed the coils and that fixed it. The codes indicated misfires as well...I think one was about a random misfire "on startup." Does that sound familiar?

 

Yes! This sounds very familiar! It's exactly what is happening. Then, if I continue to let it run, I start getting misfire codes for various cylinders. Is there an easy way to test individual coils? Or is it a better idea to just replace them all (to my knowledge they have never been replaced)?

 

You can test individual coils by moving them around and seeing which ones the codes "follow." It may be better to just do them all, though, once you get in there.

 

I'd guess it's something more global than plugs, coils or even injectors. It failed suddenly on multiple cylinders, and it's unlikely that multiples would go out simultaneously. I'd look upstream at MAF, 02 sensor, a good vacuum leak, or something in the fuel delivery system. Bad gas could be a possibility if you had JUST filled up. Something like a head gasket could trigger it too I would think, at least if all the codes were on the same side.

ECU might be 58th on my list. Share your codes--it can't hurt.

 

It is a 2005. If you have no Maintenance history proceed as if these are the original coil packs. These things fail, and sometimes they fail all at once (or within a very short time span from each other).
My 2006 did the same thing. Misfires on one, then a couple more. I would let it idle and it would get one or no misfires,other times it would have more misfires.
swapped the coils around amongst themselves sometimes the fault would follow the suspected coil sometimes it did not. I replaced all 8 coil packs and have had no misfire issues since.

Hope this helps

 

Thanks! After digging around in the GAP live values menu, I found the misfire counter, and isolated it to cylinder 8 (misfires constantly on 8, only 1 other random misfire on other cylinders) Swapped the coils around and it definitely is the problem. Ordered a whole new set and will hopefully have it back up and running tomorrow. Will let you all know how it goes. Thank you everyone for your help!