Many automotive shops get intimidated when faced with the task of working on a European vehicle. Some of the reasons for this is they aren’t familiar with the vehicle, they don’t have the correct tools, or they quite possibly think that a European vehicle is so much out of the norm or completely different from the Asian and domestic vehicles that they are accustomed to.
Keep in mind, a combustion engine is a combustion engine. They are all predominantly the same. The differences between all the different car manufacturers are what they attach to their engine systems.
Those differences are what differentiates them from the others. You still have a block, pistons, crankshaft, cylinder heads and manifolds. Fuel delivery, ignition and emission systems can be drastically different from what a typical domestic or Asian vehicle can have.
In this article I want to talk about the BMW and Mini Cooper car lines and some of the drivability issues that are associated with these vehicles. Yes… contrary to some of the beliefs, these Euro vehicles do have issues just like their cousins over the pond (see Figure 1).
The BMW marque has been around since 1916 while the Mini Cooper counterpart started around 1959. It wasn’t until 2002 that BMW first introduced the “new” Mini Cooper and the Mini Cooper S. So to automotive repair shops, the Mini Cooper is relatively new. Remember, anything that is relatively new can be intimidating… right?
So let’s look at some of the drivability issues on some of these cars and determine what we need to do to repair them.
Just like any vehicle that you bring into your service bay you have to first and foremost understand the vehicle’s control system so you can properly diagnose it. Doing a quick 10 minute read in your service information system can go a long way in aiding your diagnosis.
One thing that you need to understand is that our European counterparts like to talk about the same parts in their cars as we do in ours but they like to call them by a different name. For example, we call an ECM an Electronic Control Module. BMW calls their ECM a DME or Digital Motor Electronics. Understanding the correct acronyms helps immensely.
European vehicles also label their chassis and model numbers completely different than those of our domestic brands. For the sake of time, I will save the model deciphering breakdown for a future article.
Let’s look at a 2013 BMW 328i xDrive model with a 3.0L engine. The customer complaint was a rough running engine at idle with a slight misfire (see Figure 2).
This vehicle was not setting any diagnostic trouble codes. Using a compatible scan tool is essential when diagnosing these vehicles. It’s important to make sure that the scan tool is up-to-date as the scan tool manufacturer has added a variety of features that could make your diagnosis a success.
Whether you are using an aftermarket tool or a factory tool, the data that you are obtaining needs to be precise and accurate. Looking at misfire data on this vehicle is essentially the same as a domestic vehicle except the terminology is different. Misfire data on the scan tool is called true running value (see Figure 3).
This is a measurement of a cylinder contribution that the DME looks at. The ECM detects engine misfires by monitoring crankshaft speed. The ECM receives the input from the crankshaft sensor and determines if there is a misfire present by comparing crankshaft speed variations between combustion events on each cylinder.
The crankshaft must rotate 720 degrees (2 rotations) to fire all of the cylinders in an engine regardless of the number of cylinders. Therefore, each firing event is spaced apart and occurs at a specific time.
By monitoring the crankshaft signal the ECM can determine which cylinder is misfiring and also the severity of the misfire. If the data is greater than 0 then that cylinder isn’t contributing enough for that cylinder.
Some scan tools will have a reset for the smooth running cylinder data and some don’t. Resetting all adaptations for the particular system you are working on should be done after all repairs are made. That test kind of puts the DME back into a normal state, so to speak, similar to a fuel trim reset. It is also important to do a bulletin search whenever you are working on a drivability complaint, let alone any other problem.
Rather than spend countless hours trying to get to the bottom of a problem, the manufacturers have done that research for you and more than likely have created a fix for that particular problem.
Never overlook all the resources that you have access to. Performing this service bulletin along with replacing the spark plugs repaired the slight misfire and set the smooth running values back to zero on all six cylinders.
As our next vehicle example, we can look at a 2010 Mini Cooper S 1.6L with a customer complaint of a crank but does not start condition. This vehicle is from a friend of mine (Rusty Flake of Advanced Automotive Diagnostics and Repair of Whiteland, Ind.). This vehicle was towed in and it just cranked but wouldn’t start. Every once in a while there would be an ignition pop but no firing.
The vehicle did smell like it was flooded with a smell of raw fuel. Whenever there is a crank/no-start on a vehicle it usually boils down to a few things. It’s either a fuel, ignition, electrical or a mechanical problem. You need all four to ensure that an engine will run and you need them to all happen at the correct time. Picking which subsystem to check first is often dependent on the condition or symptom that the vehicle is presenting.
There has been a lot of talk lately of a new procedure of checking compression and valve timing from the inside out. By using a pressure transducer attached to a lab scope one can actually see the in-cylinder compression being measured and the correct valve timing of the engine all while only removing one component... the spark plug. So with the lab scope hooked up to the pressure transducer and inserted into the spark plug hole, the engine was cranked and a recording was taken with the scope (see Figure 4).
After stopping the recording, the waveform was then analyzed using the zoom feature of the scope. Here you can see the in-cylinder compression waveform that was taken. By looking at the waveform you can see that there is a valve timing problem.
Looking at the deep pockets that went below the baseline, along with where the yellow line of the pockets crosses the vertical lines, this represents the different strokes of the engine.
Right there you can tell that the valves are not opening and closing at the correct times. With that information, it was decided to pull the valve cover and do an inspection of the timing chains. The top chain guide was mostly gone and a couple of the others had chunks missing. Based on that evidence the job called for replacing the chain and guides.
After the job was completed and the engine was started, the scope was hooked back up to see what the running compression looked like at a cold idle and on a hot running idle (see Figures 6 and 7).
In order to break down the in-cylinder compression waveform, let’s look at what was happening. This cranking waveform shows just what is occurring within the cylinder (see Figure 5), showing crank/no-start zoomed.
The first part of the waveform to examine is the exhaust valve pocket. This pressure change shows when the exhaust valve opened. Under a cranking condition the target for the pressure change is 30-60 degrees before top dead center (BTDC). This pressure change produced from the exhaust valve opening is late at approximately 10 degrees BTDC. This indicates that the exhaust camshaft is two teeth off (the rule of thumb is 15 degrees for each tooth).
Now examine the intake pressure change after the 360 degree point (TDC). There is a pressure drop that occurs at 30 degrees after top dead center (ATDC). Note that this should occur at the 360 degree point.
This drop in pressure is produced from the downward movement of the piston. As the piston moves away from the cylinder head, a negative pressure (vacuum) is created within the cylinder. If the intake valve opens late, the pressure within the cylinder is already in a negative pressure state, thus the pressure drops as soon as the intake valve opens. This shows that the valve opening is 30 degrees late.
Now look at the intake valve closing that occurs after the BTDC position. The pressure change is occurring at the 90 degree ABDC (after bottom dead center) position. This shows the intake valve opening is late by 30 degrees. (Note: The correct position for this pressure rise is 30-60 degrees ABDC). This cranking in cylinder pressure waveform clearly shows the camshaft timing is approximately two teeth late (retarded). If one learns how to interpret the pressure changes that occur within the cylinder there is indeed a lot of valuable diagnostic information contained.
This is just one method of testing a crank/no-start. As I stated, you might start with a different system on the vehicle, but getting to the bottom of the problem is what’s essential in diagnosing the issue.
These were just two examples of attacking a diagnostic repair on a European vehicle. It’s essentially no different than a domestic or Asian vehicle. One of the most important things to remember when working on European vehicles is not to get intimidated. Yes, they have their differences. Yes, they do require some different tools, but that’s about it.
It’s the understanding of the system that you are working on that makes the difference. And that goes for any vehicle that rolls into your bay. Whenever you are using your scan tool or lab scope, I encourage you to build a mini library. Take multiple screen shots of what you are working on. Label them as good or bad. Label them as before and after.
A lot of technicians are sharing their information with each other. Someone might be looking for a particular screen shot or wave form that you might have and vice versa. Remember, sharing is caring and in this industry we all could use a little help now and then. ■