There is a misfire on Cyl 4 in my LR2. It's only in the morning, or when the car has been sitting for quite a while. A few days ago it would persist and i would get a check engine light. Now if I start it and accelerate the engine to 2k RPM, it goes away in a few seconds and no check engine light.

What in the wide, wide world of sports could be causing this? The plugs and coils are less than a year old, and they are Bosch coils!

 

I had a similar problem with my original engine. But it was on the notorious cylinder 6 that other owners complain about. New plug and coil, and it still persisted. I never figured it out.

Later, after the engine was replaced, I had some of the old parts in hand and sent out the fuel injectors for testing. I documented the story in this post. The blockage they found on the injector is my best guess, though I'll never know for sure.

https://landroverforums.com/forum/lr...ements-111819/

 

Cold engine might not be the cause, might just be pushing the problem over the edge when cold.

Electrical problems don't usually get better as they warm up, usually the opposite. Usually.

I'd lean towards marginal injector... a hot cylinder will burn poorly atomized fuel a lot better than a cold one.

Bur easiest to check is coil pack, swap with another cylinder and see if the problem stays or goes with the pack.

Then swap the spark plug.

Then swap injector, more of a PITA.

If that doesn't shed light I guess compression check?

 

I put a double dose of Lucas injector cleaner in the tank when i filled it up yesterday, drove for a while and this morning it started just fine. Go figure...

 

I did the same for my issue, using Techron fuel cleaner. It stopped the problem for awhile, then kept coming back until fuel cleaner didn't make a difference. Hope you have better luck.

 

Time will tell. By that time I may have already sold it.

 

It's trying to come back. I ordered a full set of fuel injectors.

 

Did you consider doing a relative compression test first? Do you have an o-scope?

 

No, and I don't think this 206k mi 17 yr old truck rates a medical diagnosis with an o-scope. If there's something worse than just a need to change old fuel injectors, I'm sure I will find out.

 

Well, sooner or later my luck was going to run out. Turns out the coolant system is perfectly sealed. But when the mechanic looked inside cyl 4 with a borescope, he found evidence of coolant. Apparently when it condenses it interferes with combustion but when the engine is hot everything is fine. For the time being I will add a head gasket sealant additive to the oil, but it's for sure I need to change the head gasket.

Anyone done that before? I know it's going to be a tough task, but is it a reasonably DIY thing?

At least I have six new injectors, and six old ones I will put through my ultrasonic cleaner and overhaul all the seals so i have them as OEM spares.