335i Misfiring

Misfiring in 3rd and 4th gears accompanied by lean AFR spikes
Straight down pipes. Dryshot

Category:

Autos & Vehicles

Tags:

• 335i
• BMW

[hotrod182]

@DwnNvr Although when it suddenly spikes up, it the fuel pressure is near its highest. And the DME seems to be pulling enrichment during those times possibly. So I'm wondering if an ignition misfire is making the dme either pull fuel, or possibly the unburned oxygen rich gases are merely the byproduct of the misfiring and not the cause?

[pimpsahan55]

So 335i not reliable car?? are these problem only on 07-09? no 2010 right?

[SneakyDeeky355]

I doubt it's your plugs, especially if you've had them for over 5 months now. I have an 07 335i (N54) with JB4 and had a similar issue. My issue turned out to be carbon build up inside my intake manifold. Multiple write-ups on E90Post and N54Tech for the DIY fix; just takes lots of time and patience. Worth it, though. My car's a beast again (although not quite as much as yours :)

[blurglide]

So....if you're running lean, maybe the fuel pump and meth are about maxed out.

You have one of the most powerful 335i's out there. I'm just running a default JB+ on mine (although at 6000'). How is everything else holding up? Any major dirvetrain problems?

[DwnNvr]

@hotrod182 No I don't have any experience with these cars. However, I have been around these types of applications. A misfire is due to either not enough gas or air. Now that I think about it for a second if I remember correctly your car runs lean when misfiring right? That points to a fuel problem. So maybe it is possible the car isn't getting enough fuel to compensate for all the air it is getting at those high rpms.

[hotrod182]

@DwnNvr I suspected that also, but they are direct injection. And they are only about a yr old.

[hotrod182]

@DwnNvr These are very specific 3 prong plugs for the N54. So it sounds plausible for this to be happening on plugs this new, and on a car that runs great off nitrous? Also, are you basing your recommendations from previous experiences on other platforms, or do you have a N54?

[DwnNvr]

@hotrod182 Or maybe a bad fuel injector.

[DwnNvr]

@hotrod182 Go buy a new set and make sure they are the right temp spark plugs for what you have in the car. If it doesn't fix the problem then you just have an extra set.. No big deal.

[hotrod182]

@tmo335tt My plugs are only about 5 months old and about 4000 miles. They are the first thing I suspected. But a nitrous shop said it sounded like lean flutter, (My AFRs are spiking to 20:1 when this is happening). But I am figuring misfiring can cause the O2 to read lean also. Its a 046 jet, dry shot. I would love for it to be plugs. Yours sounded the same way?