Is this normal from cold start JHM Stage 2

I changed my spark plugs for NGK (92400) FR7BHX-S Ruthenium HX Spark Plugs and i also had a faulty cam sensor ( bank 2 exhaust ) so i brought 4 new ones and fitted them as well for good measure.
All is fine car runs ace and is really smooth on tick over but as i was checking misfire per 1000 revolutions on the VCDS from a cold start i have been getting 1 misfire showing then it goes back to 0 it is also not on just one cylinder, yesterday it showed on cylinders 4 and 5 today it was on 8 and 4 so they are random ? It does not stay on 1 for long before going back to 0 then once the car has warmed up a bit they all stay on 0 even when driving the car at a steady pace or driving hard ! There are also no fault codes and the car runs beautifully. So i just wanted to know is this normal to see or is there a problem and if so what could it be ? Thanks in advance guy’s :+1:

Cold start in about any trim from stock to mild to wild you can expect to see some missfires before the motor is up to working temp. The combustion chamber and overall motor temp isn’t at its optimal point.

Some cars will obviously miss fire less or not at all. But this is going to be due to fuel component conditions. Temp conditions and other factors.

The colder it is out the more likely there will be more missfires. Have your SAI system trigger you can almost guarantee your going to see even more.

Given what you listed. That sounds about normal.

That’s good news then, i often look at misfire per 1000 revolutions and fuel trim to check that coils and injectors are all working correctly but never from a cold start so was not to sure if this was ok or not.

I did think that temps in the chamber and over all motor temps plus the SAI might be the reason for this but i was not to sure, so thank you @justincredible for letting me know all is quite normal i appreciate it and I’m relieved too. Top man :+1::blush:

The ECU is also firing the injectors out of phase so it can heat the cats up quickly. But as Justin said, completely normal.

Thats good to know thank you @Ape_Factory😁

What about the vacuum, any hissing? I got this running lean link

Vacuum leaks are quite common on VAGs.

I am changing the green upper intake seals as two or so have spilled a bit of burnt oil/carbon. If the hissing goes away I am gonna see if I don’t get any or almost any misfires.

I think worse gas mileage as well possibly (I have got it).

Torque to factory settings. Clearly the rubber gasket things will give way a bit over time.

As I have looked at total misfires and the occasional jumps, I wonder how many is normal at cold startup when you have a bit of carbon buildup. 2-3 maybe any more than that I would look at above.

A misfire on one cylinder could cascade to the next cylinders in the firing order?

In my experience, there hasn’t been any cascading effects.

The green seals are damn expensive. I looked at mine at 53K and they were fine but I went ahead and changed them when I swapped in new injectors recently. More of a preventive thing and I got a great deal on them.

The lower intake manifold to head seal, I replace those every time as they’re cheap.

As these cars age, the vacuum lines can and will harden/crack. I just helped a friend diagnose a flapper issue which turned out to be a cracked hose. Luckily the under-hood temps aren’t super hot and VAG uses quality hoses from my experience. Still, if you start approaching 100K miles, might be a good idea if you have the upper intake manifold off to check all the vacuum lines. If they’re no longer pliable, I’d just replace them.

Regarding the mentioned seals, I am gonna try to clean and renew them to see if any hissing sound goes away on cold start. Will probably just try cleaning with ethanol then CRC silicone spray (we get that here in the EU). That might be an option for those who aren’t willing to spend 150 - 200 USD on those. In the end wonder if annealing works on that kind of rubber. I will just replace them at this time though and keep the old ones and try as I don’t have the “toughness” to potentially have them get sucked in the engine as they deteriorate.