K Series Cold Running issue
 

Right, at my wits end with this, but can't bring myself to go as far as replacing the engine wiring loom as I've had suggested elsewhere.


Every time when starting from cold, the car will misfire until it fully warms up. Most of the time it will start OK, and then develop sometimes to the point of stalling, however every now and then it will stumble into firing up and have a miss from the instant it starts.
The severity of symptoms isn't consistent - sometimes it will be a little fish-bite misfire, other times it will stall 3 or 4 times before it runs. Does seem to be worse in the cold/wet though. And finally, sometimes when driving it feels a bit down on power for the entirety of the trip - not enough to say there's definitely something wrong, but enough to feel like its struggling a bit. Other times once it's warm it's completely fine.



It's a 1.8 non-turbo, VVC inlet manifold and ported cylinder head but both Kmaps and DVApower have said they've never come across something like this before from the inlet/head work alone.


I've done quite a bit of diagnostics/code reading/parts cannon but I don't want to start off by listing it all in case it leads people down the wrong path/into the same trap I seem to have fallen into.


Thoughts and suggestions of what to do welcome, please!

Considering the work that has been done on the head, this may seem obvious but.....


Is there any signs of coolant on the spark plugs?


regardless, I would imagine that one spark plug will be a different colour to the other three unless you have a random misfire going across all cylinders.

No signs of coolant in the cylinders/on the spark plugs.
Plugs all look the same as well, so I'd reached the conclusion that it's a random misfire across all cylinders, which is supported by no cylinder-specific codes, only P0300 (random misfire) and P0316 (misfire excess emissions).


So from that (plus a compression test that showed all cylinders to have similar, normal pressures) I've ruled out anything mechanical.
EDIT: Should also add that I've done the obvious cam timing check as well.

I would look for an inlet leak.

That was my next thought, I've lost count of the amount of times I've sprayed brake cleaner around it looking for a leak - nothing.

Even the couple of garages it's been in can't find any evidence of a leak. Plus I don't think that would explain it not starting smoothly sometimes.

What plug gap have you?

Sent from my moto g(7) power using Tapatalk

Plugs are at 0.8mm, it's even worse at the book 1.0mm!


And it's not the ECU either as Marinabrian has very kindly swapped that already.

By way of a bit of a bump.

My next thought was a TMAP or coolant temp sensor issue, so these were both replaced with no effect.


Does anyone have any thoughts on a fuel pressure problem? It's had FFS and the clip fitted, but wondering if the pressure being slightly low, but enough to run on, would do this?

When I had FFS, I just fitted an orange clip and the problem wasn't fixed. It was caused by the old and dodgy o-ring. They tend to leak once disturbed and I had opened up the filter to check it inside. Basically, it's an expensive error. Never open up the filter unless you plan to replace everything inside. Just a thought.