Audi Repair: A4 misfiring and now wont start., crankshaft position sensor, red herring

Question
QUESTION: Jan,

My 2003 Audi A4 2.0lt FSI has been misfiring for a couple of weeks, but i haven't had time due to work commitments to rectify the problem.

I have changed the plus and put a new air filter in but the problem is the same.  My car ran out of petrol a couple of months ago and I'm not sure if this is something to do with the problem or just a red herring.  

The engine management light flashes when its being driven but not all the time. I've put it through the VAGcom diagnostics which have indicated misfires on single and multiple cylinders, but usually on single cylinders.  

I had decided it was probably the coil pack on cylinder 4 (nearest the windscreen?)and played around pulling the coil packs off each spark plug to hear if i was getting a spark at each cylinder.  Initially i was not hearing the tell-tail "click" of the spark at cylinder 4, but was hearing it at all 3 other cylinders.  After playing this morning i have now lost the Spark click on all cylinders accept possibly the one furthest away from the windscreen.  The car won't start anymore so i can't get the diagnostics to check for faults.  

I am thinking i have damaged the coils packs by pulling them out while the engine is running and may need to replace all four of them. Is there a way of checking the coil packs before I spend the money on new ones.

Could there be some thing else wrong.  the car has done 90k miles and i have read from your other responses that it may be other elements that are starting to go.  

Have you any ideas on what i should do/check next.  

Jan, thank you in anticipation for any response you can give.  Its Sunday at the moment so don't suppose you're on line.  

Regards

Ian G

ANSWER: Hi Ian,

If the car does not spark at all, then it is unlikely that all the coil packs went bad.  Did you check the crankshaft position sensor already?  If you are not getting a spark at all, then the battery voltage, and the ECU should be checked.  Not really an easy way to check the coil packs unless you have another car you can try them on.  I would start by checking the crankshaft sensor and the ecu connections...  Let me know,  Jan

---------- FOLLOW-UP ----------

QUESTION: Jan,

Thnak you for the quick response. How do i check the Crank shaft position sensor (engine won't start - do i need the engine to run to test this?)and what is the ECU and how can i check this.  I feel the voltage is OK as I've looked at this with the VAGcom diagnostics.

Answer
You can test the crankshaft position sensor by connecting a voltmeter to the terminals of the sensor and turning the engine over.  You should see a small voltage blip every turn.  Easier with an oscilloscope but a voltmeter works.  If you can hear the fuel pump kick on then the crankshaft sensor is probably working.  Do you have positive voltage at the coil packs, and is the ground good?  I would be checking wiring and connectors before replacing components.  Good luck,  Jan