Would love some advice here please for things to look at. The other night the LR3 started with a rough idle. Once warmed up it was gone. The next night it did the same thing, and the CEL came on. Drove it the following day, and it was choppy when on the throttle, but when warm, was better. It got a bit worse after that. I cleaned the throttle body (wasn't really dirty) as well as the MAF. After that, it ran like a scalded dog when testing it. The next morning, it was back to a rough idle and misfires.
It was throwing codes for misfires on 1, 3, 7 and 8 as well as a misfire below 1000 RPM code. I reset them, and drove it easy and the light did not come back but you still free it. I'm sure if I drive it hard it will come back on.
Would love to hear any ideas on easy things to look for. Here are some basics:
06 with 120K
Always run 93 octane and syn 5W-30 (every 5K)
New PCV maybe 4K ago
Air filter newer
Plugs are older (but I am ruling that out due to it going from fine to misfires on 4 cylinders overnight). I will change the plugs regardless.
Coil pack is original I think (would this cause only some to misfire anyway?)
Inspected all the vacuum lines to the best of my ability, as well as the intake, boots, etc.
Other fact but likely nothing to do with it: Had the positive battery cable loosen up a week ago. Went to start it and when the power was requested from the starter, got one click and everything went totally black. Newer battery so knew it wasn't that. Tightened it up and fine since then.

 

The v8 uses coil on plug, there are 8 of them. You could try moving them around and seeing if the misfiring moves with the coils.

 

My first thought would be coil pack as well, but then you said you were reading misfire codes on multiple cylinders. I think I remember reading on an Audi forum once that a similar multiple misfire scenario was caused by a fault coolant temp sensor. If you have an IID tool, perhaps you could try recording a graph of coolant temperature and see if there are any anomalies when the misfiring starts.

 

Yes... I meant to say "coil packs" and was thinking the same as the spark plugs, that having multiple go at one time doesn't make sense to me. I really do not think it would be the coils, but who knows with these!

 

My mind was going towards some type of coolant sensor issue for a bit as well, but then went away from that. The coolant gauge works as it should, the fans kick on and off as they should and it seems the t-stat works as it should it as well. I would look deeper into it if there were multiple or random misfires. I am not ruling it out. The weather has been whacky here from 20 degrees up to 70 and back again.

 

Is there a controller that dictates when each coil initiates? I was getting misfires on my '03 Montero Sport and that was the issue. I think they called it the Ignition Spark Module or something.

 

So, I will add this in here:
I ran a can of the Seafoam spray cleaner through the truck last night. Let it hot soak for like 10 minutes, then drove the heck out of it. The first minute was choppy as it always is doing that treatment as I covered the neighborhood with a thick layer of smoke. After that it drove brilliant. Noticeable increase in acceleration and idle was perfectly smooth. In fact, not that it was loud at idle before the issue started, but it is amazing how hushed it is now. The truck ran at 100% perfect from idle through redline for the 10 miles or so I drove it.
Started up again today and back to a rough idle and all that crap (although it is still quieter than before). So, maybe it does have something to do when the engine is very cold compared to warm. Any sensor to test here? Another note, the sensor (VVT?) on the front drivers side valve cover is seeping some oil. Doesn't look like a ton, and looks like it has been doing it for a little bit. Not sure if that would play in or not.
Thanks in advance!

 

Yes. Good idea. I'm not sure if it's dictating when each coil fires, but I think there's something called an ignition capacitor or something similar that could result in similar symptoms. Let me see if I can figure out what it's actually called...

EDIT: Yeah, and I actually posted a suggestion for that part on a different post. Ignition Capacitor or "Condenser" (Looks like Radio Suppression Capacitor is the same thing but for the radio/interior) Part #LR005578
FYI: https://landroverforums.com/forum/lr...t-asked-58509/

 

I saw that in one of the diagrams, but to me it just looks like it reduces static, and doesn't necessarily fire each plug individually. Not sure, will have to look into it more.

As a side note, I changed the plugs tonight. I knew it wasn't them, but figured I wanted a closer look around so might as well do them. No unusual fouling or wear on any of the plugs. All look fairly similar.

 

Agree. That RF Capacitor doesn't do quite the same thing. I heard that if that part fails the symptom is "no start." That said, maybe the LR3 also has a "brain" to control those coils. I'd call the dealer and ask a Parts guy or a Service Advisor. They may just give you free advice if you ask the right way.