1989Type44

Last Wednesday morning I got the car started and drove it straight to Audi (Checkered Flag - Virginia Beach). I told the service rep in detail what transpired with the car. The service rep was extremely knowledgeable. I requested a complete diagnostic scan of the car. I requested they try starting the car (hot / cold) off and on for a week.
The final results from the dealership are: No faults found / No codes found / No defects notes. Car starts and runs normal. They did a through and complete test on every system. They did a full diagnostic on the engine. They did a full diagnostic on the charging system. They did a full diagnostic on the fuel system. They even checked fuel pressures at various points, pump, relay and regulator all within spec. They checked the immobilizer and found no faults. They provided a complete and detailed report. In the end they had no findings. The car has run normally since I finally got it to start last Wednesday morning.

My speculation is that this was a engine (ECU) and (Immobilizer) fault. There is a great article on myturbodiesel.com detailing how the immobilizer works on these cars and some tricks people have done to reset the POS. Those two computers talk to each other to allow the car to start. Like any computer that locks up or goes stupid it needs a reboot. Sometimes more than once. In the case of the Immobilizer it also needs to communicate with the RFID chip in the key. After replacing vacuum lines, coolant temp sensor and crank position sensor I still had no luck starting the car. The night before I did 2 hard ECU resets, I also tried 2 generic throttle body alignments and left the key in the ignition all night long. Not in the "on" position. I also relieved fuel vent pressure. The car started on the first try and died. I grabbed the second key and it started and ran ( the engine was very flooded from all of the previous starting attempts ). Ran like an old 2 stroke boat motor for a few minutes. Let car run for about 20 minutes before I was off to the dealer and had no issues along the way.

This was the biggest headscratcher I have ever encountered owning Audi's for the last 16 years.


UPDATE
Last night made several attempt to start engine. No luck.
Did hard reset on ECU (removed negative batt cable 30 minutes, reinstall and put key in "on" position for 5 min). No luck getting engine to run.
Engine smelled flooded.
Put key in ignition and left in on position for a about 2 hours with battery charger connected.
Made a couple more attempts to start engine - No luck - Crank- engine tries to run but dies.
***CHECKED FOR ENGINE AND IMMOBILIZER CODES - NO CODES STORED.
CAR HAS NOT RUN FOR 2 WEEKS NOW.
I went to work third shift and get home 0800. Planned on calling for a tow to the Audi Dealer this morning.
Go out to the car and take the fuel cap off - relieves pressure - and reinstall cap.
I get in car and discover I had left the key in the ignition all night.
Attempt #1 car fires, runs and dies with that key.
I grab second car key and put in ignition.
Attempt #2 car fires & runs. Started like an outboard boat motor.
Let idle for 15 minutes to clear out all the fuel in the exhaust
Drove car to Audi Dealership for further diagnosis. No issues during the drive.
I will make 1 more post with Audi techs determination if they find something.






2003 Audi A6 Avant - 3.0 - 130K - Very Respectfully Maintained - Never Had 1 Real Issue with the A6
For this exact problem I have read numerous posts on many forums but nobody has ever said what fixed the car.
Regardless - I will post what the fix is when I find it.
So here we go.
Yes the car is fueled.
Yes my VAG scanner works.
Battery voltage 12.75
Starter turns the engine no problem.
***Engine does not start and run. Initially it ran for about 1 or 2 seconds. Then "dies".
*No codes stored. Engine
*No codes stored. Immobilizer
Checked all the fuses. No faults.
Replaced a few questionable vacuum lines.
Replaced coolant temp sensor.
Replaced crank position sensor.
Reset ECU.
Plenty of fuel spraying out of injectors.
All 6 coil packs replaced in the last 5K miles.
All plugs replaced in the last 5K miles.
Tried both keys (No Immobilizer light remaining on or flashing).
Seems like a lot of A4 and A6 owners have experienced this issue - but nobody ever posted a definitive answer on a fix.
At this point I can only suspect an immobilizer issue.
If somebody out there knows - Please Share - Thank you in advance for any solutions or further troubleshooting advise.

jcman

VCDS will not show a fuel delivery problem with the pump or the ignition switch, I'd check the fuel pump relay and if power is always present to the pump with the ignition on and also see if the fuel pressure drops during this test.
No IMMO light no issue.

jcman

Plenty of fuel spraying out of the injectors?
How are you determining this and are the plugs soaked too??
This might suggest a problem with the fuel pressure regulator.

pr0xZen

I share similar issues with a 99 2.4 V6 (30v), but I usually do get a start after 10-15 seconds - it appears to help a bit if I blip the throttle after 5-6 seconds. With me it only happens when engine is warm. No codes, no closer to a solution or cause.

It really bugs me that VAG didn't fit the fuel rail(s) with a nipple or valve. Not quite sure how to tap in there with a gauge after the regulator.

pr0xZen

In reply to your #1 post update - Glad to hear there were some positive results. Hoping you come back here with diagnosis/feedback from the Audi techs - as you mentioned, there has been quite a number of threads on similar issues - but few that have been concluded with solutions or end results. The true resource value of these forums really goes to waste when issues are resolved but solutions and/or diagnosis are not posted.

1989Type44

Last Wednesday morning I got the car started and drove it straight to Audi (Checkered Flag - Virginia Beach). I told the service rep in detail what transpired with the car. The service rep was extremely knowledgeable. I requested a complete diagnostic scan of the car. I requested they try starting the car (hot / cold) off and on for a week.
The final results from the dealership are: No faults found / No codes found / No defects notes. Car starts and runs normal. They did a through and complete test on every system. They did a full diagnostic on the engine. They did a full diagnostic on the charging system. They did a full diagnostic on the fuel system. They even checked fuel pressures at various points, pump, relay and regulator all within spec. They checked the immobilizer and found no faults. They provided a complete and detailed report. In the end they had no findings. The car has run normally since I finally got it to start last Wednesday morning.

My speculation is that this was a engine (ECU) and (Immobilizer) fault. There is a great article on myturbodiesel.com detailing how the immobilizer works on these cars and some tricks people have done to reset the POS. Those two computers talk to each other to allow the car to start. Like any computer that locks up or goes stupid it needs a reboot. Sometimes more than once. In the case of the Immobilizer it also needs to communicate with the RFID chip in the key. After replacing vacuum lines, coolant temp sensor and crank position sensor I still had no luck starting the car. The night before I did 2 hard ECU resets, I also tried 2 generic throttle body alignments and left the key in the ignition all night long. Not in the "on" position. I also relieved fuel vent pressure. The car started on the first try and died. I grabbed the second key and it started and ran ( the engine was very flooded from all of the previous starting attempts ). Ran like an old 2 stroke boat motor for a few minutes. Let car run for about 20 minutes before I was off to the dealer and had no issues along the way.

This was the biggest headscratcher I have ever encountered owning Audi's for the last 16 years.

jcman

Interesting that the dealership has no logical answer so I'd take their findings with a grain of salt, unfortunately you had to pay for that.

Ignition switches have been known to cause problems sometimes intermittent, this was not mentioned or discovered.

The other anomaly "rare" would be if this is happening in one location and a certain frequency is blocking or cancelling the RFID chip or IMMO, my assumption is that you are in the military parked near a base......I say no more.