Dubbers, Inc.

[Euro Crew]

Background:
For some, a flashing Check Engine Light (CEL) means "ack, panic! The engine is dying"...
Settle down, the powertrain isn't going to melt-down like Chernobyl, Russia back in 1986 (history lesson).
Basically, the ECU is seeing a serious / heavy / constant misfire in the electrical ignition system.
So, how to find the problem? Easy, time to diagnose with some simple, yet effective tools.

- Disclaimer -
As always, I am NOT responsible for the careless acts of others when using this DIY as a reference.
Basically all of you are smart enough not to stab, cut, dismember yourself, the very important electrical wiring, or the paint on your car.
Be careful and take any precautionary measures that you deem necessary for completing this task.

Tools:
* VAG-COM physical interface - USB or serial connection (Ross-Tech.com)
* VAG-COM software (Ross-Tech.com)
* laptop computer
* local friend / buddy / sibling to watch computer screen

* 3/8" drive ratchet (only need if changing spark plugs)
* 3/8" 6"+ extension (only need if changing spark plugs)
* spark plug socket (only need if changing spark plugs)
* flat head screwdriver (only need if changing spark plugs)

Supplies:
* electrical tape (only if ignition coil wiring is cracked)
* dielectric grease (only need if changing spark plugs)

What Happend to Me?
On my way to work one Friday morning, the car "blipped" in power under moderate boost pressure.
Wasn't too jaded by such, but the condition worsen dramatically during the lunch break drive...
The car would horribly flutter over boost pressure of 8psi, and power lacked when I wanted over 40% applied throttle.
And on the way home the CEL finally flashed it's face; and after scanning, it's saying misfiring on cylinder #4 was appearent.
Following the process below, I found the fault to be the coil, and replace the entire set of four for piece of mind.
As always, your experiences / results / final outcomes will ALWAYS vary...

Process:
* In the event of a flashing or solid CEL, use VAG-COM to access fault codes:
VAG-COM --> Select --> 01-Engine --> Fault Codes - 02

* denote which cylinders are misfiring; DO NOT erase codes, readiness status will be lost
- drive vehicle, and go out for test drive with VAG-COM measure the misfire counts via the data-logging feature
VAG-COM --> Select --> 01-Engine --> Meas. Blocks - 08
- measure blocks 015, and 016 to see the ECU counting misfire detection; confirm the fault code is corresponding with current conditions
- have a buddy / friend / sibling watch the screen as you drive... have the spotter note when the misfires occur (should be obvious)

* power down car (not running); open hood; remove engine cover (if installed)

* first, inspect wiring from the affected cylinder ignition coil to the ECU; confirm there is no cracking of the insulation.
- If cracking / exposed wiring is present, wrap and insulate wiring with electrical tape or water proof epoxy

* second, remove the affected cylinder ignition coil and swap with an existing non-misfiring cylinder.
- remember, when looking at the engine, cylinder #1 is on the passenger side next to the timing belt
- reconnect swapped coils, and install onto spark plug
- restart vehicle, and go out for test drive with VAG-COM measure the misfire counts via the data-logging feature
VAG-COM --> Select --> 01-Engine --> Meas. Blocks - 08
- measure blocks 015, and 016 to see the ECU counting misfire detection
- have a buddy / friend / sibling watch the screen as you drive... have the spotter note when the misfires occur (should be obvious)
- with the swapped coils, you're looking to see if the misfire has moved to the other cylinder; if it has, you have isolated the problem = bad ignition coil, replace it
- if the misfire stays on the same cylinder as the fault code(s) pulled, that means either the wiring still is exposed, or plugs are faulty

* thirdly, if needed, replace plugs with OEM units
- make sure to ONLY remove plugs when engine is cool / cold
- removal and installation of plugs when engine is hot increases the risk of cross-threading plugs, and stripping the plug seat
- refer to the Bentley service manual or archived threads for correct spark plug torque specifications; correct torque is critical for no compression blow-by

* finally, after the problem has been solved, head back and clear out the fault codes stored in memory
VAG-COM --> Select --> 01-Engine --> Fault Codes - 02 --> Clear Codes - 05

Systematically, you can EASILY deduct a misfire to one of three faulty components: coils, plugs or wiring.
Using the procedure above can reduce wasted money on randomly replacing unknown condition parts; parts they may actually be good.