[jayrsilsby]

I recently installed catless downpipes on my 07 335i and flashed stage 2 with MHD. It was fine for about a week until a few days ago while merging onto the freeway, it got a misfire. I got it home and read the code 29CE Misfire cylinder 2. I cleared the codes, swapped the coil pack for cyl 2 with cyl 1, restarted the car and got 29CD misfire cylinder 1. Bought a new ignition coil and car was back to normal. On the way home from autozone again merging on the freeway, same thing happens. I get it home again and get 29D2 misfires cylinder 6.

I haven’t gone out to get another ignition coil because I’m curious if that’s the actual problem. Is it possible it’s something electrical shorting out? I just find it weird that I killed 2 in one day and that they’re different ones. I was not WOT on either occasions maybe about half throttle in 2nd gear.

[Cloverdale]

May or may not be a coil on 6. If it is a coil that's not so surprising considering your upgrades on a 14 year old car. Better a coil than an injector. I'm still on original coils with similar upgrades at 112k kilometers but have had to change a couple of injectors probably due to my valve cover leak into 5 (now remedied). I've also swapped an injector to another cylinder to confirm it was faulty. Let us know how it turns out.

[Hoody007]

Originally Posted by jayrsilsby

I recently installed catless downpipes on my 07 335i and flashed stage 2 with MHD. It was fine for about a week until a few days ago while merging onto the freeway, it got a misfire. I got it home and read the code 29CE Misfire cylinder 2. I cleared the codes, swapped the coil pack for cyl 2 with cyl 1, restarted the car and got 29CD misfire cylinder 1. Bought a new ignition coil and car was back to normal. On the way home from autozone again merging on the freeway, same thing happens. I get it home again and get 29D2 misfires cylinder 6.

I haven’t gone out to get another ignition coil because I’m curious if that’s the actual problem. Is it possible it’s something electrical shorting out? I just find it weird that I killed 2 in one day and that they’re different ones. I was not WOT on either occasions maybe about half throttle in 2nd gear.

How many miles on the car?

I'm on the original coils, injectors, and turbos at 140k with no issues, but I'm also totally stock.

Coils are the cheapest option, and you can swap between banks to isolate them…

[whyzee125]

I would replace all 6 with Eldors and new plugs too. In some cases, plugs or injectors can take out coils and vice versa.

Also being an 07 it's possible you have a mosfet issue but that would more likely manifest itself in the form of a constant misfire on one cylinder as the injector isn't getting the signal to fire. Oftentimes after this, the injector needs replaced too but unlikely this is your issue.

[lookalikehuuh]

Yeah replace all the coils with OEM Eldor coils, DO NOT USE AUTOZONE COILS. They are trash!

[charlie_m]

Originally Posted by whyzee125

In some cases, plugs or injectors can take out coils and vice versa.

Huh? How so?

[whyzee125]

Originally Posted by charlie_m

Huh? How so?

I'm not sure what the science behind it is but it's actually somewhat common.

[white46]

if 1 coil goes, then another one... expect to replace all 6.

[marvinstockman]

WOT, which gives a full charge to the cylinder makes it harder to fire the plug. A worn plug makes it harder for the coil to fire the plug.

In both cases, you can certainly overheat the coil which causes coil breakdown. Replace the coil and plug, and see what happens.