apenay

I've searched the forums already but wanted to give details also and see what you guys think.

Here's the timeline:

Wife gets home from work driving the A6.
45 mintues later we drove to dinner.
1hr 30 minute later we get in the car and the car won't start.

When starting it, it chugs like normal but the engine never fires up. We tried jumping the care but it didn't seem like a battery issure. So we left the car where it was car and got a ride home.

Many here have suggested to pump the gas pedal to the floor and to try starting it. So I tried that today after work and the car started up on the first try. I let it idle for a bit (5 minutes) then started making my way home. Halfway home the engine cuts off completely and I was barely able to pull over to the side of the street. After several attempts at starting the car I was able to get it started again but this time the engine cut off after about a minute. Another few attempts and I get the car start but this time the CEL came on. I waited a few minutes and decide to test my luck in driving it home (I was only a few blocks away). Made it home and the car is in the driveway now.

I replace the coolant sensor not too long avoid and it's reading fine also. I've check the fuse for the fuel and it's fine. I called my mechanic and he said it might be the idle air control valve.

I'll be able to VAG it later to see what codes come up. In the meantime, do you guys have any ideas?

4Driver4

Fuel pump.

Why would an idle control valve prevent it from starting?

apenay

Here's the VAG scan:

Thursday,06,August,2009,22:48:45:31952
VCDS Version: Release 805.4
Data version: 20090602



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Chassis Type: 4B - Audi A6 C5
Scan: 01 02 03 06 08 15 16 17 18 34 35 36 37 45 55 56 57 65 67 75
76 77

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Address 01: Engine Labels: 078-907-551-AZA.lbl
Part No: 4B0 907 551 L
Component: 2.7l V6/5VT G 0003
Coding: 06752
Shop #: WSC 02325

3 Faults Found:
17883 - EVAP Leak Detection Pump: Malfunction / No Signal
P1475 - 35-10 - - - Intermittent
18032 - MIL Request Signal Active (Check TCM for errors too!)
P1624 - 35-10 - - - Intermittent
18010 - Power Supply Terminal 30: Voltage too Low
P1602 - 35-00 - -
Readiness: 0000 0000

-------------------------------------------------------------------------------
Address 02: Auto Trans Labels: 01V-927-156.lbl
Part No: 4B0 927 156 DJ
Component: AG5 01V 2.7l5VT USA 1717
Coding: 00002
Shop #: WSC 00000

2 Faults Found:
18258 - Powertrain Data Bus: Missing Message from ECU
P1850 - 35-10 - - - Intermittent
17100 - Transmission Input Speed Sensor (G182): Implausible Signal
P0716 - 35-00 - -

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 8D0-907-389.lbl
Part No: 8D0 907 389 E
Component: ABS/ESP allrad D36
Coding: 06397
Shop #: WSC 06121

1 Fault Found:
18258 - Powertrain Data Bus: Missing Message from ECU
P1850 - 35-10 - - - Intermittent

apenay

So I've replaced the battery to my remote just for the heck of it since that's one of the easiest, cheapest things to do. It was a long shot but what the heck.... it didnt' work. =(

I've noticed that the car will start on the following day each time on the first try and cut out at idle after about 5 minutes.

I cleared the codes and waited a day to rescan the car and only this remained from what I can tell b/c the engine would cut off and the Vag would not be able to communicate with the controller anymore.

18010 - Power Supply Terminal 30: Voltage too Low
P1602 - 35-00 - -

The following day the car would start and again cut out after a few minutes on idle. And again the Vag is unable to communicate with the controller.

I'm starting to suspect a bad ECU especially given some of the older codes that were pulled initially. So I have some questions.

1. Where is the ECU for a 2001 A6 2.7T?
2. Would a bad ECU cause an engine to cut off?
3. How can I test to see if it's the ECU?
4. Where can I get it fix or find a cheap replacement?

Maini

Fuel Pump or a dirty Fuel Filter... When did you last change the fuel filter???

apenay

I changed out the coolant temp sensor yesterday. It didn't solve the problem. I also checked to see if the TCM was flooded by any chance and it was not.

I did make some progress however. Whenever I'm able to start the car if I rev the engine to near redline for a couple of seconds the engine would stay running. I left it on for about 20 minutes before turning it off myself. The first couple of times I did this about a cup's worth of water came out of each exhaust. It's been really humid in NYC the past couple of days so I'm not sure this is relevant.

When the car stays running I'm able to clear out the codes. I'm also able to restart without any issues if doing it consecutively but it seems to have a hard time starting again if I try again after a couple of hours. No codes reappeared after a couple of restarts except for:


Address 17: Instruments
Control Module Part Number: 4B0 920 980 M
Component and/or Version: C5-KOMBIINSTR. VDO D11
Software Coding: 02264
Work Shop Code: WSC 00000
1 Fault Found:

01311 - Information Data Bus
80-00 - Single-Wire Operation


So with this new bit of information can anyone narrow down the possible causes? It seems odd to me that the engine would stay on after revving it hard while in park. Only thing I can think of is maybe the battery gets charged a bit when I do that and it supplies the necessary power to whatever components needed even though the car is started and shouldn't be dependant on the battery anymore. Does that seem plausible at all? If so, maybe it's a weak battery? Enough for crank but not enough to supply power to necessary components afterwards?

This is driving me nuts. I'm on the fence about what to do. Fix or do cash for clunkers? I love the car when it works but I hate these surprises that can possibly leave my wife stranded somewhere.

4Driver4

Again: Fuel pump.

apenay

Should I get an OEM fuel pump or the one that RLG ended up using in his DIY?

https://www.audiworld.com/forums/sho...34&postcount=1

Any recommendations as to where to order from? I've checked ECS but they only sell the fully assembly for the OEM not just the pump. I'm weary of fitment issues in the assembly if I go aftermarket.

4Driver4

First you should test the old one. I'm making what I think is a reasonable guess. There is, however, no substitute for diagnostics.

If the pump is bad, call Joe at Axis Motorsports.