During start up- rough lide/misfire

[RS6NOR]

The MAF values and trim values look normal. No clues there. Probably no vacuum leak.

At least that eliminates some causes.

What are we left with?

More likely causes:
Bad injector(s)
Bad coil pack(s)

Unlikely causes:
Bad/Fake plugs
Bad fuel - has your car been off the road for a while?
N80 / Active carbon filter - might be worth testing.
ECU defect

You can test the injectors. I wonder if it's worth pulling the injectors and sending them for cleaning / testing?

I think I would be tempted to swap the coil packs out.

Hi,

thanks for your reply.

Ref. your comment on the coils. As i have mention before have i changed, coil and injector on cylinder 3 where you have the error code. I have double checked that it was done on the correct cylinder 3 they did the work on and they where doing it right.

Could there be other coils which are failing than the one providing cylinder 3 and still get error messages on cyliner 3?

Why is the rough idle going away after 30 second after cold start up if the coil pack are weakend/failing. would not you expect the rough idle to more frequently present also when the engine is warm?

[RS6NOR]

I still think coil or coil's and the missfire has killed the lambda's (Also quite common)

i agree that the lambda is most likely killed by the misfire.

[Shoppinit]

Maybe inside the coil pack there is a broken join that expands and makes contact when it starts to warm up.

[RS6NOR]

Maybe inside the coil pack there is a broken join that expands and makes contact when it starts to warm up.

Find it hard to believe. I would image that the temperature over the coils do not increase so fast? I also think that if this was the case the rough idle would last longer in cold weather since it would take longer to reach " connection temperature" for the joint. This is not the case, rough idle last equalliy long in cold and warm weather...

[Shoppinit]

Fair enough. Good luck.

[RS6NOR]

A bit in the dark about what should be my next step in the hunt for my rough idle cure... My list of next steps (which i have limited faith in) are as follow:

1 Tempted to start by changing out all the coils for a complete set of new ones...
2 then change all the injector with new ones...
3 then change the ECU with a new one...

If not any of that helps i am completely lost...

Comments?

[Ryan_Pestell]

Where abouts are you in the country?

[grizz]

Is the car using water ?

I've had a few with head gasket failure that misfire on start up .

[PhilT]

Is the car using water ?

I've had a few with head gasket failure that misfire on start up .

+1. Mine didn't use water though.

[RS6NOR]

Where abouts are you in the country?

I am located in Norway.

[RS6NOR]

Is the car using water ?

I've had a few with head gasket failure that misfire on start up .

I have not noticed that the car uses water. If leaking fluid i guess there should have been alarm related to low level in expansion reservoir?

I suspected this quite early and there was done a leak test on the cooling water system. They where not able to find a leak.

Can it be that the leak is small ( droplets) such that the accumulated volume is to small to notice?

[RS6NOR]

Is the car using water ?

I've had a few with head gasket failure that misfire on start up .

Which procedure will you suggest when verifying if the top gasket is fried or not?

[bilko1]

Drive the car until it is at normal temperature, take home and park up overnight. Next morning open bonnet remove no 3 coil and plug and look in cylinder for water ingress. This will be easier with an endoscope camera. If you see a small amount of water / coolant you have either a cracked head / block or head gasket failure which is small and seals with heat expansion. A friend recemtly came across this on an R8 that the local dealer couldn't diagnose.

[Shoppinit]

Is the car using water ?

I've had a few with head gasket failure that misfire on start up .

Which procedure will you suggest when verifying if the top gasket is fried or not?

Rule 44: Grizz will only post once in any thread and never reply to further technical questions on that thread.

OK, it's not an official rule, but I think we should make it one.

[mavada]

Rule 44: Grizz will only post once in any thread and never reply to further technical questions on that thread.

he will post twice max if he smells there could be a future customer...but thats all because hes busy...