This seems like it could get expensive

[Glutton4punishment]

I have an issue that I have never seen before and hope someone here may have some insight.
2011 Z4 35i with 60k miles on it. It is still mostly stock with Dinan stage two software update and a center cat delete. I haven't added or changed anything in the last year or so and it has run very well up until now.
So here's what's going on.
The car runs perfect cold or hot as long as I don't let it go into turbo boost. Once it starts to go into boost it starts to miss fire and sets a code for miss fire on 1 and or 4 or if I really push it both. But that's the only code. Here's where it gets weird. Once the misfire starts it will not stop no matter what I do. But as soon as I stop and restart the engine the misfire goes away and stays away until I try to hit boost again. Plus the motor runs great, its smooth with good torque in fact if you didn't know something was wrong you would never know it.
My first thought was weak spark but I don't understand what restarting the car would have to do with resetting the coils. I thought maybe it's fuel delivery. But shouldn't reducing fuel consumption by backing off of the throttle get it to stop misfiring?
I'm stumped. Have any of you experienced anything like this before?

 

[Milan]

You are probably misfiring and hitting limp mode, which is getting cleared when you restart your car.

Start with new spark plugs and coil packs. Probably need injectors too but start with the easy stuff.

 

[NoGuru]

Yep. what Milan said. If you have a way to get logs that will tell a lot too.

 

[Glutton4punishment]

That makes sense! I didn't think of limp mode.

 

[NoQuarter]

Yes. You described what everyone here is troubleshooting about 90% of the time.

You have nothing weird going on at all.

 

[Glutton4punishment]

I have to admit I completely forgot about limp mode. The misfire and limp mode felt very similar, at least in this case it did. The instant return to semi normal threw me off.
I have my coils and plugs ordered and will report back with my results.

 

[Lurcher]

What they all said. FCP can set you up, tune up time....


And you own a BMW - there is a tax to pay...

 

[Glutton4punishment]

Here's the follow up to this thread.
My parts arrived yesterday. I purchased a package from Turner Racing that included some BavAuto coils and some standard heat range Bosch plugs. With parts in hand I was ready to tackle the job. Before I proceeded I took the car out on an errand. It run very well and no matter what I did I could not get it to misfire. Up until now I have been able to reproduce the misfire at will. The only change that I can see is that the weather has cooled down and there is much more moisture in the air.
Reluctantly I went ahead and installed the new coils and plugs. Wow am I glad I did! It made a very nice difference. Not a huge difference but definitely a noticeable one. On start up it came to life with a new crispness and a smoother idle. A very nice gain in low to mid rpm torque. With strong top end pull and NO misfire.
This is one of those situations where the performance of the coils slowly but steadily degrades over time until they finally start to act up. I didn't even notice the loss of performance. You sure can tell the difference when you replace them.

Cheers,

 

[derekgates]

Here's the follow up to this thread.
My parts arrived yesterday. I purchased a package from Turner Racing that included some BavAuto coils and some standard heat range Bosch plugs. With parts in hand I was ready to tackle the job. Before I proceeded I took the car out on an errand. It run very well and no matter what I did I could not get it to misfire. Up until now I have been able to reproduce the misfire at will. The only change that I can see is that the weather has cooled down and there is much more moisture in the air.
Reluctantly I went ahead and installed the new coils and plugs. Wow am I glad I did! It made a very nice difference. Not a huge difference but definitely a noticeable one. On start up it came to life with a new crispness and a smoother idle. A very nice gain in low to mid rpm torque. With strong top end pull and NO misfire.
This is one of those situations where the performance of the coils slowly but steadily degrades over time until they finally start to act up. I didn't even notice the loss of performance. You sure can tell the difference when you replace them.

Cheers,

Awesome! The coils can develop hairline cracks that cause issues in humidity. I, too, have replaced coils a few times (and have a box full of them) as well as some BL coils to install.

This reminds me of my MKIV GTI (VR6) in which all 6 coilpacks were in an epoxy block that would hairline crack and force a replacement of the 'coil' for all cylinders. That got to the point the community made brackets that housed MSD coils..

->

Oh German cars...

 

[Lurcher]

With 60k - time to clean some valves too...

 

[Glutton4punishment]

With 60k - time to clean some valves too...

I recently walnut blasted the intake valves when I replaced the Valve cover. In fact over the last year I have had nothing but problems. Water pump, replaced Valve cover, replaced Transmission cover and now coils. If I were to try and read into the future I suspect the next thing to fail will be one of the two fuel pumps.

 

[derekgates]

I recently walnut blasted the intake valves when I replaced the Valve cover. In fact over the last year I have had nothing but problems. Water pump, replaced Valve cover, replaced Transmission cover and now coils. If I were to try and read into the future I suspect the next thing to fail will be one of the two fuel pumps.

You are me during the last year.

Walnut blast, valve cover, HPFP, DCT flush, coils... turbos are next.


N54 is the quickest zero to poverty car on the market!

 

[Lurcher]

Get some spare cables ready for the roof, and you are good to go for another 60k - assuming the radiator and hoses have been swapped too....

Oh, and I forgot about the turbos... I'm sitting at ~45k, decisions to be made in next 2-3 yrs (only 3-4k per year)...