European diagnostic tips

Aug. 26, 2014
European vehicles with drivability problems can and do get turned away from the service bays by many of the best technicians around because they’re just not comfortable working on them. But it doesn’t need to be that way.

European vehicles with drivability problems can and do get turned away from the service bays by many of the best technicians around because they’re just not comfortable working on them. But it doesn’t need to be that way.

True, the systems can seem a bit strange, and special tools are often needed to diagnose or repair systems properly.  And it’s also true that the parts on those vehicles can be really expensive, so misdiagnosis just isn’t an option. But there’s good money to be made under those hoods, so it’s worthwhile getting to know how to diagnose the problems and then fix the systems when they go wrong.

As tempting as it might be to avoid working on these vehicles, if you’re up for the challenge it can be very rewarding and often not nearly as bad as you’d think. With a solid plan of attack and a few diagnostic tricks you really can diagnose and repair drivability concerns on European vehicles quickly, accurately and profitably. Here’s how.

Here’s the Plan
Older European systems were unlike anything most of us were used to, so it was tough to figure out how they even worked let alone how to fix them. However, from experience, vehicle control systems and components on newer models seem to be getting very similar to each other no matter where the vehicle was built, especially in the lower-priced vehicles. In fact, it’s not uncommon to actually see another manufacturer’s part number or logo on something when you open a vehicle’s hood or open a parts box.

This is somewhat reassuring.

Because vehicles need the same things to operate properly no matter where they’re from (air, spark and fuel in the right amounts at the right time with good compression/unrestricted exhaust also at the right time), this means that the faults that cause drivability issues are also becoming much the same among different types of vehicles, no matter where they’re from.

For example, a heavily restricted air filter or a partially plugged fuel filter will cause, among other things, a lack of power in a vehicle no matter what type of vehicle you’re working on or which logo is on the steering wheel.

So because the vehicles’ needs are similar and the systems are similar, the diagnostic strategy for European vehicles’ drivability problems is, therefore, very much similar as for other vehicles.

To diagnose the problem begin by listing the things that could cause that particular issue and create a reasonable suspicion about what could be causing the problem (maybe by most likely to least likely), and then test each theory, taking readings and measurements and testing each system to eliminate or confirm your suspicions until you’ve located and corrected the concern, and conclude by verifying the repair.

You know, just like you could do for any other vehicle – really, it’s not that bad!

Just In Case
Just as with any other type of vehicle, it’s a good idea to inspect the simple things first, before you get too involved in the diagnosis.

If you’ve ever been deep into testing a system and then realised that a blown fuse or something similar and obvious caused the problem, you know why it’s so important to start any diagnosis by quickly inspecting the simple things that introduce problems into the systems.

Start by looking for what else doesn’t work, possibly indicating a problem in a common or related fuse, ground, connector, splice or module.

Also check to see if any work was done on the vehicle recently, which might have caused the problem. Along those lines, see if the vehicle has an alarm or aftermarket systems such as remote starters or fog lights that might have gone bad after years of faithful service.

And finally, look for spills, goo, blockages, debris or junk under the seats or near the sensors that could affect operation. Coffee spills on consoles that then indirectly seep into control modules are not uncommon.

Getting Started A great way to begin diagnosing – besides checking for blown fuses and the like – is by looking for Diagnostic Trouble Codes (DTCs) even if the Malfunction Indicator Lamp (MIL) light isn’t illuminated. And this brings up an important point: It’s really important to know that without a good scan tool that can accurately and reliably read codes and data (not all of them can) you’re in for a real diagnostic challenge. In other words, you need the right tools to do the job.

True, you still can check for the obvious causes of the problem and you might get lucky, but in most cases – even if the MIL indicator isn’t illuminated – hooking up a scan tool and checking for codes is one of the first steps in diagnosing any drivability problem. Checking for programming updates usually comes next, because sometimes the only way to repair a problem is by reprogramming a module, and it’s nice to know that before wasting too much time testing other things.  The reality is that without a good scan tool, diagnosis will be difficult if not impossible for all but the luckiest of techs.

When you’ve retrieved any codes or relevant data, checking for both Service Bulletins and Technical Tips is another important preliminary step, especially documents that mention updated parts to fix problems. Note that some manufacturers have both Service Bulletins and Technical Tips and they often have different information about different issues in them so checking thoroughly can pay off.

Additionally, searching the online technicians’ resources (iATN, Identifix, etc.) is a great and completely responsible preliminary diagnostic step, because let’s be honest, it’s a fantastic resource for professionals, especially if you’re not familiar with that system. However, randomly searching the Internet and chat forums (like customers seem to do) is definitely not the same thing as learning from your fellow professional techs about pattern failures or diagnostic steps. The first is a great way to get an idea of what could be going wrong before proving that that is or isn’t the issue you’re dealing with, the second can be full of very bad advice and horrible ideas.

Internet-assisted diagnosis may not be the most respected way of solving problems but it certainly can be a timesaver when you’re stuck.

Where to Begin
Obviously there are many, many things that could be causing drivability problems, and you’ll need to narrow that huge list down as quickly as possible, because time is valuable.

A good way to prepare to diagnose the problem is by finding out from the customer things like when the problem occurs, if it’s intermittent or constantly there, if it only happens when the engine is hot or cold, or if the problem happened suddenly or developed gradually over time. Then use this information to eliminate or highlight suspect systems and prioritize diagnosis on the most likely faults.

If the problem developed over time, tend to suspect and investigate systems where things or deposits build up gradually such as air of fuel supply systems. If the problem appeared suddenly rather than developed slowly over time, tend to suspect electrical or electronic components and inspect those first. In other words, if a customer says, “All of a sudden the vehicle stated to misfire!” suspect ignition components or modules. If a customer says, “The problem started as nothing but it’s getting really bad!” suspect air or fuel systems (and exhaust systems, too – blocked converters do happen).

If you do suspect an electrical problem, wiggling wiring harnesses and connectors before you’ve duplicated the concern might not be the best plan. You might inadvertently fix the problem without realizing it and then you won’t be completely sure the problem is gone. Leave things as they are during the diagnostic stage, wiggle and poke later on.

Continuing On
There are a few key things that cause drivability concerns. From experience, one of the more common drivability problems European vehicles develop is a hesitation or lack of power – which may or may not set codes. This doesn’t need to be difficult to solve, but you need to go in with a systematic plan of attack.

Air filters and housings are usually a good place to start looking for problems. If you’ve ever tried to run with a stuffed up nose, you’ll understand why a plugged air filter can cause a hesitation. Engines need to be able to breathe freely, and performance suffers when they don’t. One tip, our rodent and bird friends have been known to make nests in the filter housing using the air filter itself for nesting material, even if the vehicle is parked in an underground or covered garage. If that’s the case, it’s a good idea to wear a mask and gloves when removing the debris since inhaling the fecal matter can cause respiratory problems.

Just as on any other vehicle, worn spark plugs can and do cause problems as does using the wrong plugs or the wrong gap. I mention this because a customer recently came in with plugs gapped to the widest spot on his gapping tool (he’d done his own tune up earlier). Damaged spark plug wires or coils also can cause drivability problems. If you suspect one of these components may be faulty, swapping a suspect coil to a different cylinder and checking if the problem moves along with it may help speed diagnosis.

A dirty throttle body or plate will also cause problems. This can be a tricky repair though, since the strong solvents in some cleaners can damage the component, and even if it doesn’t the system may need to relearn how to idle when the job is complete. This problem has happened on newer vehicles with high mileage so it’s worth keeping in mind during your diagnosis. This one is actually pretty easy to check – just look for build up in the passages. From experience, European vehicles do tend to be high-mileage units, so carbon buildup on valve seats is also a possible cause of drivability concerns.

Problems from a plugged fuel filter are common on older European vehicles simply because the fuel filters can be notoriously difficult to replace. And because this can be bad for the fuel pump, it’s a good idea to check both fuel pressure and volume if you suspect something in the fuel system is malfunctioning. Sixty psi doesn’t mean much if there’s too little fuel volume to feed the engine’s demand.

Along those lines, bad gas has become surprising more common lately, even though it’s not usually one of the first things to be checked. If a customer mentions that the vehicle has been in a situation where bad gas is a possibility, like the vehicle being stored for extended periods of time or using questionable fuel additives it might be worth investigating further. Another recent customer wanted to save money, so instead of using premium fuel he added multiple bottles of octane booster to each tank of regular fuel figuring if one is good, five is better. His logic with the octane booster is debatable, but adding that much additive is very wrong. He and the vehicle seemed normal in every other respect so this came as a surprise. It shows that a good discussion with the customer is so important when diagnosing problems – you just never know. If you disconnect the fuel line and notice the fuel is discolored or smells strange, you may have found the cause of the problem.

And as with any other vehicle, low compression or base engine concerns can cause drivability problems. This can build up gradually over time or develop suddenly – particularly after a timing belt change or head or block repair. Timing belts on European vehicles are notoriously tough to set up correctly. Being off by a single tooth on one of the cams can and does cause drivability problems. Painting your own match marks using white out before the old belt comes loose can really help prevent problems.

Conclusion
Diagnosing drivability problems on European vehicles can be worthwhile and profitable. The systems are similar to ones you’re likely already familiar with and the problems that develop are also very familiar. With a plan of attack, understanding of what can go wrong and how to prove or disprove those suspicions, and a good scan tool diagnosing the concerns can be relatively straightforward and your bottom line will thank you for it.

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