Cylinder 2 misfire cold start

If it is still only cylinder #2 then it has to be something specific to cylinder #2, but in the last 12 months you have changed most things, so here we go:

- We know the car is 2005, but how many miles/Km?

- It could be the low voltage wiring to the coil or a bad connection on the coil on #2, check the cable and connector for any signs of damage/dirt.

- Is there anything near the coil on cylinder 2 that could be causing an issue?

- the reason for asking about the spark plug colour last November was I wondered if you had a split head gasket on cylinder 2. I know you have done a compression test and #2 is similar to the others, but if you have a split in the head gasket this might let coolant water in to #2 when it's cold and just stood. This would cause a misfire when cold.

The ways to test for a failed head gasket are:

- loosing coolant or boiling the coolant when the engine is hot;
- a spark plug which is 'washed' clean;
- you can get a dye kit which shows if you have water in the cylinder;
- steam or light white smoke from the exhaust;
- a smell (sweet) from the exhaust;
- look under the oil filler cap, is it emulsified or milky brown like a milk shake?

The car has 320000 km. And before 6 months the cylinder head was repaired with new gaskets etc. I was waiting when the weather gets cold to see if the problem is solved, but there was no difference.
There is no coolant loosing.
I was thinking that there is something with the wiring or ecu problem but I can't explain why ot happens only with cold weather and engine.
Is there a way to check the cylinder 2 injector if its working properly while the engine is running?

I don't know that injectors are easy to check, but you swapped it over and the problem didn't move, so it's not likely to be the injector.

The injector wiring or ECU might have a fault/bad connection, but that is unlikely if it is OK when warm.

Did the car do this before the cylinder head repair?

Yes. It was the main reason I made the repair

If you take off the black plastic cover and start the engine from cold in the dark, do you see any sparks where high voltage is escaping to the rocker cover?  I can't remember if cylinder 2 has the coil pack, or if it's fed from a pack on cylinder 3.

Dimitris wrote:

Yes. It was the main reason I made the repair

Unfortunately for you the repair to the cylinder he’d hasn’t fixed the problem, either it was never the cylinder head/gasket that was at fault or it still has a leak.

One thing we haven’t asked is how much does #2 misfire, is it just under acceleration or is it all of the time when cold?

Member facade suggested a burnt exhaust valve that is lowering the compression when cold, but is ok when warm, did you check the valves when the cylinder head was off?

It is possible a worn valve guide allows oil to enter cylinder #2 when cold, but not when warm.

A cold engine misfire often occurs through lean mixture, this could be a faulty injector, but you swapped these, an air leak, low compression when cold, a timing issue, etc.  However, it’s specific to cylinder #2, that rules out a number of things.

Could you arrange to check fuel pressure when cold, especially to injector #2 and check cold compression, look for lower compression on #2 compared to the others.

Then take all four spark plugs out, clean them very well, put them in and only run the engine at cold, hopefully with a misfire.  Take the plugs out and take a clear photo of plug #2 compared to the others, we are looking for a difference in colour?

If it isn’t a valve or cylinder head, I wonder if a worn cylinder barrel or broken piston ring would cause the problem, but only when cold, it’s a high mileage engine and a number of engine components might have wear.

The misfire seems to be alla the time when is cold. The valves are new and the engine doesn't burn oil at all.
I will check the spark plugs soon and the compression too.
I need some days to find time to check that. I will post the results as soon as possible.
Thanks a lot

Finally I think I solve the problem. After searching the wiring loom, I found a damaged cable (not totally) which going to the cylinder 2 injector. I repair it and today morning, with low temperature, the problem was gone.
Hope that will not bother you again for that.
Thank you all for your time 

Intermittent electrical problems like that can drive you crazy -- good work finding the cause. Thank you for updating us on the solution!

Good stuff!

DrRobin wrote:

If it is still only cylinder #2 then it has to be something specific to cylinder #2, but in the last 12 months you have changed most things, so here we go:

- We know the car is 2005, but how many miles/Km?

- It could be the low voltage wiring to the coil or a bad connection on the coil on #2, check the cable and connector for any signs of damage/dirt.


 

Good news that you found the problem.

I did wonder if it was the low voltage wiring in my post on the 29th.  The issue is when cold you need a better spark and when cold, the battery gives less output, so all you need is a resistance joint (or some leakage) and you get a misfire.

Robin