N54 Misfire Troubleshooting

[TheMilkManz]

Hoping to get any help I can from the community. I have been reading misfire posts after misfire posts and now my eyes are bleeding. I haven't found anything similar to what I am experiencing. Hope someone can point me in the right direction.

Basically I have a persistent cylinder 5 misfire. The car only misfires after it has been driven for some time with several stop/starts in the middle. So drive somewhere for 10 minutes, shut car off, turn back on within ~ 5 minutes, drive again for 10 minutes, shut off again ...then on the 3rd or 4th start it will start misfiring and throw a service engine soon light. When this happens, it is obvious there is a misfire but I still have boost and the car is not thrown into limp mode.

Things I have done:
New Battery (was 10 years old anyway)
New Spark plugs (gaps were triple checked)
New Coil Packs (also swapped them around and always shows misfire on cylinder 5)

When I drive the car cold from point A to B, the car does not misfire or hesitate at any RPM. It is only triggered after car is warm and cycled Start/Stop a few times.

My next guess would be both fuel pumps and/or injectors. I'm just at a loss that those would be affected in this manner. Is there an easy way to diagnose those without replacing? I'm JB4'd with DCI and Chargepipe, otherwise stock.

Any help is appreciated! Thank you.

[optigrab]

How many miles?
Was your battery properly coded?'
When did you last clean your DCI?

When was the last time your JB4 was updated and adaptations reset?

I would also confirm your settings with someone over at n54tech they can be set incorrectly

[TheMilkManz]

Car has 110k miles now.
Yes, the battery was coded but the issue was happening before and after the battery swap.
I cleaned the DCI a few months ago, could use another cleaning maybe. I'll give that a try.

I have not updated my JB4 since buying it off a member here and have never cleared adaptations. Guessing this is something saved in the JB4? I will have to look into this, thanks!

[optigrab]

It very well could be an injector if they are original but they are expensive so start with the cheap stuff first. Even if you just swap the injectors the tools are 80$

[QuebecDIY]

In doubt, I would start with the basic: I would do a compression test on all cylinders. That is going to give you an idea of the mechanical health of your engine. It is not so complicate to do.

1. Relief fuel pressure (you can watch my video to know how to do so)

2. Unplug all coil packs and Remove all coil packs and spark plugs
3. Install compression gauge on cyl 1
4. Crank engine (start) until pressure is not rising any more on gauge (typically 3 - 4 shots) - push start button again to stop cranking
5. write down compression you obtain for cyl 1
6. Release pressure from your gauge
7. Repeat from step 3 for all cylinders

Compression should not vary more than 29 psi between cylinders.
Normal compression is around 203 psi, wear limit is at about 145 psi.

I had an issue on a Honda CRV with miss fire. Everybody is changing coil, distributor, and so on. I have checked compression, and one cylinder was 0 psi. I have then decide to remove the cylinder head and check visually. It was a burned out exhaust valve.

When your engine is cold, the ECM is not able to fully analyse the engine management. Because it is not using the oxygen sensors until it reaches its operating temperature. When its cold, it runs kind of blind a bit with some other parameters from other sensors and reference tables built in. Once it's at operating temperature, then its on its game, managing air/fuel ratio and optimizing it by checking all parameters and oxygen sensors feedback. That's why you might have the issue only when its at operating temperature.

I have some coil packs miss fire on my 135i sometimes when if I don't use it for sometimes... I check the miss fire code. I swap coil packs between cylinder (for example 2 and 5). Erase the Check engine codes. Re-Start. Normally, if it's the coil pack, the code will shift from cyl 5 to cyl 2. It happened to me recently that it was still cyl 5. I removed the coil pack, checked that the spark plug was not loose (don't strip your threads by over tightening). Then I put back the coil pack, trying to push it well/better in. I think I had to remove it and put it back 2 -3 times. Then it went away by itself (like the connection between spark plug and coil pack was not good).

Hope this helps.

[AlpineTi]

When was the last time you had the valves walnut blasted? Also is your valve cover the original, or has it been replaced?

[Dackelone]

It sounds like an injector. Next time this happens... go to the exhaust tips and see IF you can smell raw fuel. Then you will know. IF you do not smell fuel... I would suspect it is carbon buildup on your valves. This is generally a $500 repair to walnut blast them. The intake manifold has to be removed. IF your oil filter housing is leaking... then do that too - to save on some over lapping labor costs.

Their have been many versions of injectors. I think we are now up to Index #12 or #13 now. The valve cover has been known to crack over time. But that just causes a rough idle, not a miss fire.


I think what I would do first to to swap the coil and plug from number five cylinder with another... probably number four since its easier to get too than cylinder number six. Then see IF your problem still persists.

Dackel

[TheMilkManz]

Thank you everyone for the replies! Much appreciated.

Valve Cover Gasket was replaced a couple 1,000 miles ago. Carbon cleaning was done about 7k miles ago. I think that should be ok for a little longer.

I ended up swapping #5 and 6 injectors and the misfire followed the injector. That bank has all index 11 injectors so I will replacing the faulty one with an index 12. Crazy that it failed only when hot. I will post an update if that resolves it.

I still would like to do a compression test to get an idea of where my engine is @QuebecDIY so thanks for the info. Hoping for consistent numbers!

[Mr Gasser]

Assuming the faulty injector would not make a clicking sound if you held a long screwdriver against it and listened to the handle for vibrations.