2006 BMW M6 Misfire V10 – Faulty Ignition coil – Stuck in Cylinder Head

This 2006 BMW M6 V10 came in rough running with a misfire. The misfire was easily located and diagnosed, but trouble arose when the coil at cylinder 10 broke. The top electrical connector portion snapped off when the mechanic was attempting to remove it from the engine.

This tech note is more about how to I got the coil out verse the usual diagnostic study.

The tech attempted to extract the coil using needle nose hose pliers, but it would not budge. The rubber boot was stuck to the spark plug and it was slowly falling apart with each attempt at removal.

To remove the coil, we drilled a hole in the center of the coil top.

Then we screwed in a 3 mm sheet metal screw with a washer.

Next, using the nub on the valve cover, we levered the coil out using a prybar. Now be careful when you get to this point. The coil is brittle and you will only get one shot at it.
levering coil out

You can see here how dry the boot was and the brown residue inside inside.
dry boot

Be sure when installing the new coil to apply a small amount of dielectric grease to the boot to prevent this from happening in the future.

2005 BMW 325 P0171 P0174 227 228 Fault Codes Dinan Stage 2

The BMW had fault codes 227 and 228 stored (P0171, P0174) indicating a lean fuel system. This means the vehicle is running lean and the DME has tried to correct the condition but has reached it upper limit. Fault codes 227 and 228 are specific to a fault when the engine is at part throttle (not idle). This tells us that it’s unlikely the lean condition caused by and engine vaccum leak.


First I ran engine until it reached operating temperature. Then monitored fuel trim at idle using my scan tool. As you can see the Idle Load fuel trim is normal.

Next I went for a drive in the vehicle. I ran the engine through each RPM range from idle, steady cruise to WOT (wide open throttle). You can see the Part Load fuel trim is indicating a lean condition, (by adding fuel) during my entire test drive. Part Load does take some time to update, so I suggest a 15 minute test drive at the minimum.
During my test drive I am able to eliminate many possible causes of the lean condition. For example; I monitor Idle Load fuel trim at idle to see if it could be a vaccum leak. That coupled with freeze frame data ruleda vacuum leak out.
I also perform a WOT test on the fuel system. If the oxygen sensor holds above 800 mv for the entire time I am at WOT, the fuel pump and fuel delivery system can deliver enough fuel. Next I check the engine and exhaust system by looking at G/PS or Kg/H. This reading tells me about engine efficiency. I can estimate the amount of air at a given RPM, therefore testing the MAF sensor without touching it.

The 325 had Dinan performance software and an airbox, or what they refer to as Stage 2. I was convinced the problem was with the Dinan components but I have only an hour to prove this to be correct.

The airbox in modified by introducing a cold air intake, removing a baffle and changing the filter from a panel to a version of a cone style.

Here’s what I did.

I found the area where the baffle was removed (Dotted White Line) and temporarily mounted a piece of plastic in place.

I plugged the cold air intake port with a plastic cap.

Next I reprogrammed the car back to the factory DME software.

I went for a test drive, repeated the same RPM ranges as my previous one. The Part Load fule trim began to drop into an acceptable range.

Next I contacted Dinan with the information. They agreed to write a custom DME map for this car. Once I received the map I programmed the car again with Dinan’s MIP tool. It took a week or so to receive the new DME map, so the vehicle owner had to drive with the MIL light ON.

Once programmed I test drove the vehicle aagin, within the same RPM ranges. You can see part load came back down to a normal range and the vehicle is no longer exhibiting a lean condition.

This is a tricky fix. Without my standard fuel trim drive cycle test (to test components during the test drive), I may have replaced parts that were not faulty. It is important to approach each and every fuel trim fault the same way. A structured test plan will build confidence and make quick work of these common faults.

BMW E39 M5 Dual Mass Air Flow MAF Testing Specifications

Use the following information as an aide when testing BMW E39 dual MAF sensors. Keep in mind, a problem with mechanical engine components can affect MAF readings and besure you have a solid base engine before condeming parts.

KOEO (Key On – Engine OFF)taken at sensor back probing with DVOM
B1 AFM 1.02 Volts
B2 AFM 1.02 Volts
Using scan toolBoth AFM sensors read 0.9 Volt on GT1 under maf data stream.

Hot, engine running at idle taken at sensor back probing with DVOM
B1 AFM 1.30 Volts
B2 AFM 1.29 Volts
Using scan toolBoth AFM sensors read 1.0 Volt on GT1 under maf data stream.

2500 RPM taken at sensor back probing with DVOM
B1 AFM 1.85 Volts
B2 AFM 1.75 Volts
Using scan toolBoth AFM sensors read 1.5 Volt on GT1 under AFM data stream


IAT sensor not used on bank 2 AFM. However sensors are interchangeable.

Testing using a labscope. In Park or
Neutral, parking brake on.
Snap throttle to reach max voltage output.
(scope pattern shows a dual trace of both
The sensors should be within 0.1 volts of each other.