6_Myles

Hi All,
I have a cold start misfire that happens to throw a code, maybe once a month and have been chasing various possibilities.

The codes:
P0300 - Random Misfire Detected (Pending, Current, Permanent)
P0305 - Cylinder 5 Misfire Detected (Pending)
P0306 - Culinder 6 Misfire Detected (Pending)
P0308 - Cylinder 8 Misfire Detected (Pending, Current, Permanent)

P0420 - Catalyst System Efficiency Below Threshold (Bank 1) (Permanent)
P0430 - Catalyst System Efficiency Below Threshold (Bank 2) (Permanent)
(I have American racing LTH, race cats and mid-pipe)

What I have replaced:
PCV (but did install a catch can at the same time)
New spark plugs 1-8
New injectors 1-8
New coil pack #8 & #5 (these are the two that pop up the most)
New upstream o2 sensor on bank 2 (5-8 side)
Switched up where I buy gas

Mods:
ROW boxes and MAF
Green Filters - oiled


It's always tied to that bank, but always only 3 of the cylinders not all 4. Most of the time it's 5,7,&8...sometimes just 5&8, sometimes it's 5,6,8....just weird.

The car only has 29.5k miles and has a great service history, so I do not expect cam plates or lobes (not saying it isn't, just trying to rule out the easy stuff first)

I've sprayed carb cleaner around the intake and idle wasn't affected at all (when it was hot...maybe should when it is cold?)

Got any other thoughts?

if it matters this is for a 2011 e63.

As always, appreciate any thoughts.

apoptosis

Did the misfires start before converting to ROW airboxes and oiled filter?

6_Myles

They did

Cwagon

Mine did the exact same thing tonight. when I started it up with lots of oil smoke.
I did a diagnostic with my Carly and showed similar malfunctions as op above.
I let the car run like this during the checking then turned it off and back on after clearing codes.
Now runs smooth as.
I'm wondering if it was oil in the intake that contaminated the O2 sensors as I had moved my car 3 times around our driveway during the day.
I have had the oil smoke happen before after short engine running like moving car out of garage and back in after a few minute.
But it never ran rough like it did tonight.

sickSVT

Mine used to get cold start misfires every once in awhile. I would have to turn off the car and restart it to make it go away. After replacing both upstream O2 sensors it hasn't done it ever since.

Cwagon

My yearly service is coming up so will replace both upstream O2's then.

6_Myles

Hi all,

Still dealing with this issue, and today i got a real noticeable misfire…enough for a flashing check engine light. Shut down the engine and restarted and it was fine. Codes were for misfire in #5 & 8 again.

In addition to the work in Post #1, i replaced the o2 sensor on bank 1, just in case…but clearly that didn’t help.

Would secondary o2 sensors cause this problem?

Any other sensors to check, because it’s clearly something caused an actual misfire this morning.

blurred

Pull and check all of your plugs, are they wet? is it oil (valve guides/rings) or coolant (could be headbolts failing and allowing coolant into the cylinder if you are on the faulty ones/not replaced)
Could be throttle body plate
Can you verify your fuel trims?
Could be air pump issues


Because it clears up it leads me in the direction of cold starts which would be mechanical (liquid in cylinders or fouled plugs) or air pump airflow related

6_Myles

Thank you blurred, i will check into those.

6_Myles

Cold start this morning with my HP tuners hooked up. No CEL.

Lambda fuel trim b1 starts at 1.0, drops down to .87 at its lowest and then back to 1.07. B2 seems to match the same.

44 misfires on Cy 8, 10 on #2, 3 on #3&7, 1 on #1

spark efficiency did drop to like 41%, not sure if that is normal.

MAF sensors stay pretty close too

also, no smoke on startup has ever been noticed.

6_Myles

Now that I think about this data…I should probably check injector and coil pack wiring on #8

6_Myles

Checked the wiring...everything looked good. Checked vacuum and secondary air lines....looks good too. Double checked pcv conncections and all is well there. HP Tuner file is attached if anyone wants to take a look. I'm really at a loss.

Edit: I've noticed the long term trims between banks 1 & 2 are way off. Short term trims are close enough. Bank 1 starts at 8.6% and Bank 2 starts at -1.6%. It jumps up to B1 16.4% and B2 is 2.3%

As always, thanks!

gmore

Not quite the same and may not be your issue, but I had a bout of random rough idling - could restart the car and things would be smooth again until one time I started it and it sounded the the engine was blown - was my camshaft adjuster. Just an idea.

eightysixtuned

have you completed a compression check?

6_Myles

Hi Barry, I have not. Given the lack of burning oil, coolant, and it running like an absolute animal after 5 seconds of idling….that didn’t even cross my mind.

With the LT fuel trims so imbalanced, I am going to throw some downstream o2’s at it and see what happens then.

If not, looks like I’m pulling a compression test and checking the cam adjusters…in that order.

eightysixtuned

downstream o2 sensors do not control fueling and will not impact anything.

6_Myles

Update:

Replaced both downstream o2 sensors last night and had, for the first time ever, 0 misfires on cylinder #8 during startup. Got 1 misfire on #5 and 1 on #1…. But that feels normal.

I’ll give it a couple of weeks and see if this is the new normal or if I end up back where I started.

I sincerely appreciate everyone’s input and help on this one.

6_Myles

Well, the success was short lived. Backed to the normal condition.

lol

6_Myles

Alright, i'm digging into the secondary air injection system and have a couple of questions. I turned the pump on via Xentry this morning and can hear it running, can't say I've ever noticed it before. I do not have any SAIS codes.
1. Should the air pump turn on in a KOEO scenario? I have a really loud exhaust so if it only runs for a few seconds after startup, I likely would not ever be able to have heard it.
2. How loud should it be? During the test it was quite audible from inside the car with the hood closed but the driver door open.
3. Does anyone know how to test the valves in Xentry? I only found the pump test.

As always, thanks for any guidance.

Nathan Grimmer

Is the car mapped at all, could be over fuelling on cold start?

6_Myles

After drilling down into it, after replacing some hardware, this seems to be the issue. Best we can determine is that I had a failing o2 sensor or injector while we were doing the initial tuning. So when I updated to the ROW boxes, and updated my o2's...the tune was just throwing too much fuel during start up. Working through the tuning side right now with Barry.

Nathan Grimmer

Great news, tunes are often overlooked but when they aren't right, can lead to going down rabbit holes

Koyafresh

did you end up figuring it out?

6_Myles

I did! But it will be hard to pin down because I decided to pull the intake manifold and sand/paint/reseal/new throttle body plate while it was out....I didn't see any signs of cracks or leaks in my throttle body/intake but decided to do it all 'while it was in there'.

It could have been a combination of a bunch of small leaks that I addressed but I have only received one misfire code on start-up since then....and that was after sitting for a long time in really cold weather.

blay127

glad you got it sorted out. which throttle body plate did you install?