[ore0fllamp]

Any help is appreciated;

N54 335i 2008 130k miles

I am misfiring at idle only on cyl 3, no other codes. Drives fine outside of the idle, has power and is smooth no misfiring above idle. All stock, never tuned.

Car has brand new OE Bosch plugs and coil packs,
Walnut blasting was just performed 3 weeks ago, bank 1 (where cyl 3 is) has index 12 injectors.

Anything else I am missing that could be causing this?

Sorry if this topic seems beat up, I am fairly frustrated as I was having misfire last week on cyl 1 non stop. Changed bank 1 injectors with index 12 since they were index 6. Ran fine after changing them except now misfire on cyl 3 but ONLY at idle. I thought it was coils as I just changed out the original ones for the first time but the problem still persists. Tried swapping in the old plug into cyl 3 didn't make a difference either.

[arkie6]

The next logical thing to do would be to swap coil #3 with a different cylinder and see if the misfire moves with it. You could have a degraded new coil or poor connection. Also, make sure that your coil electrical connectors are fully pushed onto the coils. Don't just rely on the cam action of the connector clamp to push them on, but give them an extra push onto the connector with your hands.

[ore0fllamp]

Originally Posted by arkie6

The next logical thing to do would be to swap coil #3 with a different cylinder and see if the misfire moves with it. You could have a degraded new coil or poor connection. Also, make sure that your coil electrical connectors are fully pushed onto the coils. Don't just rely on the cam action of the connector clamp to push them on, but give them an extra push onto the connector with your hands.

I pushed them in good for sure, and what would the chances of the new set of 6 coil packs end up with a bad one on the same cyl seems pretty slim. Plus outside of idle it runs perfect?

[ore0fllamp]

Attached is a photo of some readings where CYL 3 is going into the red and much higher than any other cylinder. Not sure what it means?

[arkie6]

Originally Posted by ore0fllamp

I pushed them in good for sure, and what would the chances of the new set of 6 coil packs end up with a bad one on the same cyl seems pretty slim. Plus outside of idle it runs perfect?

It wasn't clear to me that you had the mis-fire on cylinder 3 before you replaced the coils. I agree it seems unlikely that a new coil on cylinder 3 would be the cause of continued mis-firing on that cylinder, but lots of people put lots of money on wagers with much worse odds. Swapping coils is about the easiest thing you can do to eliminate that as a possible cause. If the miss isn't electrical in nature, then you are looking at fuel or compression.

Did you code your new injector flow and energy values into the DME?

Did you reset adaptations after replacing injectors, plugs, and coils?

[ore0fllamp]

Yes, coded injectors. I swapped out the injector #3 today with another new index 12 injector that my parts guy warrantied. Coded injector, car started semi rough but smoothed out within a minute, probably because today I got a tablet downloaded MHD and tuned the car while I was at it. Since it was the plan and I got the MHD for logging and just couldn't resist lol

So this cold start after changing injector and installing the stage 1 tune resulted in a smooth idle after about 10-15 seconds. Was smooth idle for like 10 minutes so I took her out for a spin. With the tune now she goes like a bat out of hell LOL.

Anyways after a couple blocks and a few short WOT pulls 2nd and 3rd gear I returned home to park in the driveway and idle. Rough idle is back, not tossing any codes at all (as the MHD cleared codes after flash) except 2FA3 - DME: no coding. Not sure what that is have never seen it before but no misfire codes popping up anyways as of yet, and I mean above idle and WOT the car runs perfect. I'll get more time driving it as the week goes along.

Some quick measurements I saw were AF ratios on sensor 1 and 2 were about the same at idle 14.7 ish. Rail pressure was about 700psi at idle and low pressure was around 80psi at idle.

[JuniorB]

The next thing is looking for vacuum leaks. High engine heat, plastic and rubber can only last so long. There hasn't been a whole lot of bad 12 injectors out there, and the new coil and plug just adds suspision to a vac leak. Most of the above leads to a high rpm misfire.

[ore0fllamp]

Originally Posted by JuniorB

The next thing is looking for vacuum leaks. High engine heat, plastic and rubber can only last so long. There hasn't been a whole lot of bad 12 injectors out there, and the new coil and plug just adds suspision to a vac leak. Most of the above leads to a high rpm misfire.

So today I compression tested bank 1 (cylinders 1-3), all was good around 170-175psi.

One thing I noticed was the plug in cyl 3 was alot cleaner looking than cyl 1. Picture attached. (Picture cyl 1 left cyl 3 right)

I then swapped them for fun and went for a highway drive. Removed them after and now the blackened one from cyl 1 that was in cyl 3 is clean looking.
(Picture of single spark plug)

Not sure it related but I found a crack in the valve cover, however my vacuum at idle is reading -9.7psi so close to around -18/19inHG which seems normal right? The crack is however right next to cyl 3 where I am having the misfire.

[ore0fllamp]

VALVE COVER CRACK 101---- *Fingers crossed*

So I cleaned the area, ruffed it up with 400 grit sand paper and properly JB welded the crack and area. (When I say properly I know its not a proper fix but there is a proper way to use JB weld and other similar epoxy products on plastic)

After letting the JB weld set and sit for 2 hours, I went ahead and put everything back together, (I need cowl deletes badly ) then started the car. Too my surprise, the idle was much smoother and no misfires. However with that being said it has done this before after adaption resets on semi cold starts and acted smooth until oil temps reached normal temperatures.

We shall see, this morning when I went out and started my car to warm up for 10 minutes before heading to work (was like -6C this am) it started rough. I went back inside and when I went back out I had a hard misfire cyl 3 and check engine light. Had to turn the car off and back on to get it to run normally and just continue with the "normal" misfire only at idle so I could drive to work without sounding like a lawn mower lol

Anyways I ordered a new valve cover, should get it by the weekend so I can just swap the whole thing out anyways. I don't mind replacing parts that need it since I am going FBO by summer and going to run stage 2+ and beat it daily ...... I hope

[arkie6]

How is your coolant level? A coolant leak into cylinder #3 would effectively steam clean the combustion chamber including the spark plug.

[ore0fllamp]

Originally Posted by arkie6

How is your coolant level? A coolant leak into cylinder #3 would effectively steam clean the combustion chamber including the spark plug.

This did cross my mind, but I just changed the water pump and thermostat 2 weekends ago as well. After adding coolant and running the pump cycle and topping off the coolant I haven't had to add anymore, and the low level light hasn't come on.



So this morning;

Cold start was great really smooth no misfires at idle. I'm only 5 minutes from the expressway and stopped at once traffic light (it idled fine no misfire). Did my expressway trip to work and didn't get stuck at anymore traffic lights or anything.

The next time I idled was in the work parking lot (remember I'm not having any issues outside of idle) and my oil was fully up to normal operating temperature. Sure as shit, misfire at idle on #3.

Maybe the JB weld cracked? Or let go who knows. Not going to bother with a smoke test at this point as I should have a brand new VC arriving by Friday so I can install this weekend. I guess even if it doesn't solve the misfire it will prevent PCV issues and smoking.

What kind of vacuum should be going on in the crankcase at idle? Yesterday I opened the cap while running and it was super easy to open while running and there was like little to zero vacuum.

[ore0fllamp]

Originally Posted by JuniorB

The next thing is looking for vacuum leaks. High engine heat, plastic and rubber can only last so long. There hasn't been a whole lot of bad 12 injectors out there, and the new coil and plug just adds suspision to a vac leak. Most of the above leads to a high rpm misfire.

I actually replaced all of the vacuum lines, when I did the boost solenoids. Outside of all the lines that come off the vacuum pump, there's only the the one on the intake manifold to operate the DV's. And there's some vacuum line that plugs into the throttle body not sure which one that is.

[ore0fllamp]

UPDATE;

So although this sounds crazy. After coming to a dead end, having replaced literally everything (installed a brand new valve cover just now) and having a MSD81 DME so no worry of MOSFETS going bad. I decided to switch injector #1 with injector #3 thinking okay maybe there's a slight chance that both the first and the replacement index 12 injector that have been in cyl#3 are bad.

Sure as shit, misfire moved to cyl #1.

2 bad index 12 injectors if you can believe it.

Some thing that is interesting to me is this;
both of the index 12 injectors that are bad have rates 587/236 and 587/235
the other 2 injectors that are good are similar too 540/208 and 540/213

Hopefully my thread will come in handy to someone else who runs into this problem. Will update when a 3rd injector goes in

[arkie6]

Where are you getting your index 12 injectors? New OEM or re-manufactured or ?

Having 2 out of 6 injectors have the exact same energy value seems suspicious. Having it twice with 6 injectors is even more suspicious. There was a guy on here a while back that posted that all 6 of his new index 12 injectors had exactly the same energy and flow rate. There ain't no way that is legitimately happening.

About a year ago I replaced all of my 6 injectors with index 12 from FCP euro and not a single number, energy or flow rate, matched another injector.

[AZM40i]

Just throwing it out there. I was chasing a rough idle/miss. It was all over the place. Long story short, replaced all the basics, coils plugs and injectors. New vc housing. Nothing. Tried some plugs from a n20 running a step colder. Out of a buddy’s car. Bam. Smooth as silk.