Vehicle details:
WDB2100622BXXXXXX
2001
E240
M112 2.6L V6 +-215000 km

I have a rough idle with noticeable misfires.
I connected my OBD2 reader and found code P0305(Cylinder 5 Misfire Detected).
I left the vehicle to idle and checked the values returned by the lambda sensors and noticed voltage dips on the second bank sensor, see attached images. I plotted bank1 Lamda voltage, bank2 lambda voltage and engine RPM, engine temp at 92C.

From the data I assume that there is an injector on bank2 that did not inject fuel as the low voltage registered indicates an oxygen level close to atmosphere. Conversely a spike in voltage would indicate en excess fuel and therefor a faulty coil pack. And from the misfire in cylinder 5 I assume injector 5 is the culprit. I removed the electrical connector to injector 5 and an open circuit fault was immediately stored indicating that the ECU will detect a wiring problem to the injector. My feeling is that injector 5 is at the end of its life causing it to not inject at times and also causing the fluctuations in bank2 lambda sensor voltage. It fluctuates wildly when compared to the bank1 sensors.

Can any one with experience with the ignition system provide insight into my assumptions?

Attached Thumbnails

     

It could also be dirty, and/or the seal could be leaking.

I would suggest buying some new o-rings (same top and bottom), cleaning around it thoroughly (to prevent dirt entry) and then pull it and inspect it and swap it with a neighboring cylinder, renewing the o-rings in the process. Reset codes and see what you get.

Good luck.

before removing the injector and other bits, replace the spark plugs and retest, If the problem persists then swap an ignition coil from another cylinder.

I had a misfire problem and the culprit was worn out OE spark plugs at 160,000 miles.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Can't Know, will give it a try this weekend. Are you referring to air being sucked in around the injector?

Zulfiqar, I ruled out the plug as I assumed this would show a higher voltage on the lambda instead of a low one due to unburnt fuel entering the exhaust. I have piston slap, and suspect cylinder 5 as the culprit again so have been eager to pull those plugs for a while to check for fouling due to oil....its just such a mission to get to them! The car has 215 000 km so nearing the point where you had to replace plugs.

One question I have is that if there is a spark problem and the fuel is sent down the exhaust with a full compliment of oxygen, will this show a high or low voltage? Lambda sensors are ideally designed to measure the amount of CO entering the exhaust?

I also could not get the system to run closed loop. I went for a drive and ended with coolant temp at 92C but the control was still open loop due to low temperature. Where does it get the temperature to determine the change to closed loop?
This accounts for the voltage levels around 0.8v which is too rich in my mind. Stoichiometric is at 0.47v.

the O2 stream can be questionable as its an old sensor and old sensors go lazy as time proceeds.

your best remedy would be to start with changing the plugs and swapping coils - once both runs fail then you are left with two possibilities - fuel or compression.

Thats the fastest way to determine the fault with the least expense.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Agreed. Going to swap coil 5 with one on bank 1 tomorrow and remove those plugs to see what they look like. Just need to rule them out first if possible.
I don't think age is causing the problem as the data from the two banks are reasonably consistent and the bank 2 sensor is picking up fast dips indicating quick response to the change in O2 level.
Will post the findings.

Can you swap the injector to see if the problem moves?

Also, I just looked at the graph and noticed the different axes. Which bank is up around .83 volts (senses too rich mixture)?

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Prost!

Moving the injector is the most work so Im going to move the coil first and replace the plug, just looking for a source of compressed air first to clean out the plug cavity.

Referring to image 3:
Range 0.785 to 0.840 is the yellow line, Bank1 Lambda(colour not visible on the axis)
Range 0.1 to 0.9 is the blue line, Bank 2 Lambda
Range 680 to 725 is the red line, Engine RPM

The colours stay the same for all the graphs but the ranges on the axes differ. Bank2(blue) is the problematic one. Both of the banks are running rich because the fuel system is running open loop due to insufficient temperature.

Just exchanged Coil 5 with coil 1 and recorded the attached data.
Coulours refer to the same sensors as described above.
Misfires are still present although the data looks better than yesterday. Yesterday I tested over a 15min period but couldn't today due to rain.

Attached Thumbnails

     

how are the plugs? are they factory original to the engine?

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Don't know yet, going to try and remove them today to take a look.
I will only replace ignition components with OEM.
The coil packs are OEM, I noticed coil5 has already been replaced by the previous owner as it has a newer part number.
The previous mechanic that worked on the car also spilled a lot of oil on the second bank. I found a lot of thick oil inside the electrical connections to the coils, have started cleaning that out too.

Very cool setup.

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Prost!

Although it works incredibly well, it's not very refined.
Im going to add the ability to test sparkplugs/ignition coils tonight, obviously not while conducting injector tests at the same time....

Wouldn't looking into the cylinder with a camera through the spark plug holes be easier than pulling the head?

__________________
-diesel is not just a fuel, its a way of life-
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'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)