First post here guys (and gals) so be kind. [img]data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7[/img] Not new to forums, just this one.

I have a 2015 LR4 HSE Lux, 68K miles, that is throwing misfire codes. Saturday morning was around 18F degrees here in Chicago and it happened on the cold start only. Once the engine warmed up not more than a minute, I was able to clear the codes with a basic scan tool I have. After that it was fine the rest of the day...even with the car sitting for hours before restarts. Unfortunately my scan tool doesn't allow me to go too in-depth. (Yes, I ordered an IID scan tool but it won't be here for a while yet.).

Codes are P0300, P0302 and P0303 on Saturday and on Sunday morning add P0301 to those as well (and 22F degrees). (Screen shots attached.) Seems to me one entire bank. Again, they clear with my current scan tool and don't come back but I'm beginning to see a pattern here with the temps perhaps. Other cold start days haven't affected it up to this point, which leads me to my next point.

So, what have I had done to it recently? Had the passenger side valve cover resealed for seepage/leak by what I thought was a competent mechanic and don't know if the two are related or not based on the fact that he probably had to disconnect quite a few vacuum lines and maybe even the spark plug wires to get to it. At this point all I'm looking for are some obvious possibilities I can fiddle with before I go back to the mechanic and ask him to have another look at it. I'm decently competent under the bonnet but if it's beyond my skill level pay grade I'd at least like to go into it with him with some confidence knowing what it *might* be. TIA!

 

I was just talking to a Rover mechanic friend about my occasional P0307 and P0316 misfire codes, and he suggested I run a can of CRC GDI Intake Cleaner through it. I haven't given it a try, yet.

 

Someone was explaining to me that in order to take the valve cover off to reseal with a new gasket you have to disconnect the fuel rail and pull out the injectors. In my case the passenger side valve cover was leaking and that would be the bank of 1, 2 and 3 cylinders, which is where I'm getting my imsfire codes. If the mechanic didn't think...or worse yet didn't know to use a new seal and O-ring kit for each injector, he said fuel could be leaking down into the cylinder. On colder days on start up the engine could be calling for more fuel and if the car sits overnight (first start of the morning in my case) the excessive amount of fuel in the cylinder would most likely be causing the misfire. Sooooo, I have that to look forward to.

 

The codes are coming from opposite sides of the engine so unlikely to be related to the cam cover replacement.
I had this persistent headache and after replacing a couple of coil packs it came back to other random cylinders.
I ran 2 cans of the expensive cleaner (BG 44K) through it to no avail.
After a lot of research I replaced both lower/rear O2 sensors which isn’t difficult or expensive (£40..ish/each trade) which solved the random issue.
I had also recently swapped out all the spark plugs which was a pain but not impossible. Didn’t solve the issue but they were 145,000 miles old.

Good luck.

 

I think you’re assuming the cylinders are numbered odd/even. I believe the V8 followed by the odd/even numbering, but I think the V6 petrol was numbered consecutively (cylinders 1-3 on passenger side).

 

Fair enough….
My fault I hadn’t twigged it was a V6 however my professional opinion advice still stands.
I think personally it’s a waste of time putting cleaner through it but obviously won’t cause any harm,

 

@Daveykid Did you ever get word back from the mechanics on this? Please post back when you find out the problem. Thanks.

 

The following day the CEL cleared itself and it has yet to come back. I've been waiting for it to happen again but so far absolutely nothing. On one hand I'm thrilled but on the other I'm like WTF?

 

Thanks for reporting back. Hopefully it’s resolved. Good luck.