[HoonsE90]

I think I am going to go insane (almost)
Some backstory:
2009 335I at 154k miles
Index 12 injectors (unsure of install date/mileage)
Stock tube
The bad: Misfire on cylinder 3

So, I replaced all spark plugs and coils with OEM replacements. Misfire persisted. Swapped plugs around and coils, misfire stayed at cylinder 3. There was some gunk on the spark plug threads of cylinder 3 which I had noticed.

So… my next item to check was the fuel injector. I pulled it out, disconnected coils, and cranked the motor. No leaks from the injector. Replaced seal and reinstalled injector. Car ran fine for a little bit, about 20 miles or so, then crapped out again.

Here’s how it usually goes. I’ll drive the car in the morning and it’s good for maybe 20-30 miles, runs perfect. Then I start to feel the misfire come on and it goes hard.

So now I’m thinking it could be one of 3 things:

A cracked VCG, but upon inspection mine is not leaking and I don’t see any cracks.

HPFP is failing, but it had been replaced around 90k miles

Or- it needs a walnut blast. Hasn’t been done in about 30k miles, however I know that it could potentially cause a misfire, but only on cylinder 3 exclusively? Seems odd.

Maybe it’s just the fuel injector that craps out?

Any advice would be appreciated. I’ve done a LOT of reading on numerous threads and I’ve never had a misfire rock me this bad. Any advice would be appreciated. Thank you!

[swellengear]

Try swapping injector 3 with injector 2. (Don't forget to code them) If the misfire moves, then you know its a bad injector.

What codes are you getting?

[HoonsE90]

Originally Posted by swellengear

Try swapping injector 3 with injector 2. (Don't forget to code them) If the misfire moves, then you know its a bad injector.

What codes are you getting?

I can try that as well, that’s not a bad idea. With my primitive scan tool I’m just getting cylinder 3 misfire, that’s all.

Last night on my way home (I had to leave the car sitting for a few hours since it crapped out on me) I decided to push it. About 4-5 WOT pulls going up to redline, zero issues. Drove home perfectly fine. I’m wondering what that could mean lol

[HoonsE90]

Got the car to throw a misfire today. Driving around more aggressively to try and get it to rear its ugly head. Two codes for cylinder 3 misfire and 1 for cylinder 1. Not sure what’s going on there. It does sputter here and there on warm start idle, if that offers anything

[HoonsE90]

Other info:
Found out I had MSD81, checked MOSFETS they are all good. Found out my car actually has JB4 installed (piggyback), will see if I can use that to get some data logs. Car was driving fine today, after maybe 20 minutes of some harder driving it began to misfire. Cylinder 3, however cylinder 1 also showed its head as well. I’m leaning to think that I either have a crack in the valve cover towards cylinders 1-3, or I’ve got some nasty build up front. Potentially a clogged cat? Or bad o2 sensor? Since cylinders 4 5 and 6 seem awfully peaceful.

[Podunk]

you need a way to datalog and read the log. that way can check HPFP performance, and LPFP performance fuel corrections, timing corrections ETC, i would NOT push the car in it's current state, unless you want to blow up the engine.

[HoonsE90]

Good point, I’ll look into data logging. And good point, I should just focus on getting it to be able to drive for more than 30 mins and not throw a misfire.

[HoonsE90]

Picked up some injector seals from BMW. Going to swap cylinder 2 and 3 injectors to see if I can get that misfire to move.
Cylinder 3- 578
239

Cylinder 2- 573
234

Seems to be pretty close for the fuel injector ratings which is good so I can drive for a little bit without some coding. All index 12 and aiming to keep them in the same bank.

Anyone know if I just installed a new Teflon seal two days ago if I need to replace that one as well?


If misfire stays on 3, time to remove intake manifold and get ready for a walnut blast

[HoonsE90]

Misfire moved… thank god. Time for a new injector

[HoonsE90]

Picked up a new used index 12 for $150. Checked it out, yellow hue to lettering, no scraped off numbers, and metal engraving as well so it is legit. Popped it in to cylinder 3 (with a new seal) and drove it for about 60 miles on the freeway, uncoded. This morning I took it to get coded for $40 by an Indy shop since I’m taking it on a 70-80 mile drive today and wanted to get it coded and was unable to source a k+scan cable in time. So far so good and runs smooth. Will do a walnut blast next and just did a coolant flush so hopefully she will be a happy girl

[swellengear]

Originally Posted by HoonsE90

Misfire moved… thank god. Time for a new injector

Happy Days!