[SOLVED] Cylinder 1 Misfire - P0301 / P0300 Mystery
 

Turned out to be incorrectly installed keepers on one of the exhaust valves (cylinder 1), causing an exhaust leak.

***

Hi! Looking for help to track down a misfire on cylinder 1 for a 2007 e70 4.8i. Any help appreciated

P0301 - Cylinder 1 Misfire [0029CD]
P0300 - Random Misfire [0029CC]

Check Engine Light On
Rough Idle Cold & Warm
Some hesitation under load
All new Plugs
All new Coils
Cleaned Vanos sensors
Switched plugs and coils around (cylinder 1 & 2, 1 & 5), even tried old plug/coil in cylinder 1, no change in code
Changed coolant hoses (to fix a rotted fitting and associated leak)

Have replaced Valve Cover gaskets and all related sensor seals (vanos, eccentric shaft, upper timing cover, vacuum pump etc) during valve stem seal replacement
Have replaced worn crankcase vent pipe (was leaking)
Smoke tested (paint can/mineral oil from ebay) and see no leaks from intake or crankcase

I haven't had a compression test done yet, however, there was no misfire or roughness and no CEL (at least not like now) prior to all the work done above (all at the same time) even though it leaked oil/coolant and smoked like crazy.

I did have the engine partition off to make room and so I could replace all four major parts. The lower center piece was a pain.

I checked the voltage to cylinder 1 fuel injector and wiring and listened to it tick, all numbers matched specs and it sounded like it was operating correctly.

I'm wondering if water/moisture from rain during the 2 weeks I had the engine apart might be the cause. In ISTA - the Oxygen Sensor State for Bank 1 doesn't fluctuate at all (no mater the engine state) like bank 2 does. Fuses are good (30 amp under the footwell).

I'm new to INPA/ISTA but here I've attached an image of the value I'm talking about.

Check compression. Looking at oxygen sensor voltages when you have a dead cylinder is probably just going to confuse you.

Feels like there is something causing one bank to hit the rails on AFR- which is causing the misfires. NOT a 'dead cylinder'.

Air leak, broken hose, crack, etc perhaps

Thanks both.

I am going to get a compression test done and have the gaskets for the intake manifold in case there's a leak I can't see with the smoke machine. Don't have the seals for the injectors though, and would like to replace them since I'll be in that area.

Lot of money to spend on something that prolly wont tell you a thing...

Trick is to look for a leak. NOT replace parts willy nilly hoping you guess right.

IMO

Tried looking for a leak multiple times with a smoke machine, no luck. Might look into UV dye and see if maybe my eyes are just not good enough. :D

Haven't done anything since the holidays/freezing cold hit, except finally get something to log the fuel trims.

Dropbox link for anybody that cares to take a look. Bank 1 stuck in open loop it seems.

https://www.dropbox.com/s/x793oob08z...12018.xls?dl=0

Where did you input the smoke from the smoke machine? If you have not already done so, it's good to input the smoke from the oil filler cap; with the intake sealed off. Snap-on (Blue Point) makes a blue stretchy rubber smoke machine adapter that will work with our oil filler hole. Second, Snap-on sells smoke fluid that has a UV dye in it; ($$$$$) so you can use a UV flashlight and those yellow safety goggles to better see a small leak. Third, you need to have somewhat pressurized smoke to work well...not sure that your paint can will do that; does it connect to your shop-air?

I have the smoke paint can hooked up to shop air with a regulator dialed back to 3-4 psi. I've tried the following smoke inputs:

• crankcase vent pipe to intake manifold (left vent pipe itself connected to left and right side, plugged the middle connection)
• directly into the vacuum pump where the booster line connects, since it's bolted directly to bank 1

I have not tried directly in the oil filler cap, wasn't sure about there, so thanks for the suggestion. One place I've thought about but also not sure was the dipstick tube since I've read people having small leaks there.


I removed the intake boot and just put a rubber glove + rubber band over the throttle body (works great!). You get to see the pressure build and it seals well.

Since it's too cold to do anything, been trying to learn more about fuel trims and 02 sensor data. As I (currently) understand it, since sensor 1 & 2 are wideband, then 0.0 mA = stoichiometric. Positive number means going lean, negative means going rich.

Looking at the numbers from a Carly Gen2 adapter + OBD Fusion (pro), looks like Bank 1 is much leaner than Bank 2. I measured 900 pts (changes in reported values) and compared them, along with RMP and saw the following:

Average Bank 1 - .505mA
Average Bank 2 - .163mA

Average difference between the two over that time = 434%

This appears to be more evidence of unmetered air/vacuum leak... ? Sprayed Carb cleaner around Cylinder 1 fuel injector and intake while watching RPMs, didn't notice any changes.

This data is meaningless if you're got misfires or a disabled cylinder pumping raw air into the exhaust. This creates a lean condition the DME can't possibly correct. You've ruled out the coil and plug, I would replace the fuel injector.