glhglh

2004 Audi A6 Allroad Quattro:
Over the past three months, ;we have replaced all coils and plugs. Also found 1 vacuum leak and replaced the connection for that about three months ago. About a month ago, the car started to miss. A scan showed the following results:
Address 01: Engine Labels: 078-907-551-AZA.lbl
Part No: 4Z7 907 551 S
Component: 2.7L V6/5VT G 0010
Coding: 07755
Shop #: WSC 02325
VCID: 53AB78A9A1798480CC7
WA1YD64B74N013322 AUZ7Z0C2415712

3 Faults Found:
18032 - MIL Request Signal Active (Check TCM for errors too!) P1624 - 35-10 - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected P0300 - 35-00 -
16689 - Cylinder 5 P0305 - 35-00 - Misfire Detected
Readiness: 0000 0000

After replacing coil # 5 (for the second time in 3 months), the car ran great, and the follow-up scan showed:
Address 01: Engine Labels: 078-907-551-AZA.lbl
Part No: 4Z7 907 551 S
Component: 2.7L V6/5VT G 0010
Coding: 07755
Shop #: WSC 02325
VCID: 53AB78A9A1798480CC7
WA1YD64B74N013322 AUZ7Z0C2415712

No fault code found.
Readiness: 0110 1101

Two weeks ago, my daughter was driving the car and filled the tank at ARCO. No immediate problems, but a few days later, the car started to miss so bad that the car could not even make it up a slight incline. We though it might be the gas, so put a can of HEET in, made it to a gas station and filled with premium gas.

When I got the car back, I ran a scan with the following resulte:
Address 01: Engine Labels: 078-907-551-AZA.lbl
Part No: 4Z7 907 551 S
Component: 2.7L V6/5VT G 0010
Coding: 07755
Shop #: WSC 02325
VCID: 53AB78A9A1798480CC7
WA1YD64B74N013322 AUZ7Z0C2415712

12 Faults Found:
16684 - Random/Multiple Cylinder Misfire Detected P0300 - 35-00 -
16688 - Cylinder 4 P0304 - 35-10 - Misfire Detected - Intermittent
16690 - Cylinder 6 P0306 - 35-10 - Misfire Detected - Intermittent
18032 - MIL Request Signal Active (Check TCM for errors too!) P1624 - 35-00 -
17538 - Fuel Trim; Bank 2 (Mult) P1130 - 35-10 - System too Lean - Intermittent
17536 - Fuel Trim; Bank 1 (Mult) P1128 - 35-10 - System too Lean - Intermittent
16685 - Cylinder 1 P0301 - 35-00 - Misfire Detected
16485 - Mass Air Flow Sensor (G70) P0101 - 35-10 - Implausible Signal - Intermittent
17978 - Engine Start Blocked by Immobilizer P1570 - 35-10 - - Intermittent
16689 - Cylinder 5 P0305 - 35-00 - Misfire Detected
16687 - Cylinder 3 P0303 - 35-10 - Misfire Detected - Intermittent
16686 - Cylinder 2 P0302 - 35-10 - Misfire Detected - Intermittent
Readiness: 0000 0000

We then cleared the codes, and ran a scan again a few hours later:

Friday,12,October,2012,15:06:31:36044
VCDS Version: Release 11.11.4
Data version: 20120807
glhglh

Chassis Type: 4B - Audi A6 C5
Scan: 01 02 03 06 08 15 16 17 18 22 34 35 36 37 45 55 56 57 65 67
75 76 77

VIN: WA1YD64B74N013322
Address 01: Engine Labels: 078-907-551-AZA.lbl
Part No: 4Z7 907 551 S
Component: 2.7L V6/5VT G 0010
Coding: 07755
Shop #: WSC 02325
VCID: 53AB78A9A1798480CC7
WA1YD64B74N013322 AUZ7Z0C2415712

3 Faults Found:
18032 - MIL Request Signal Active (Check TCM for errors too!) P1624 - 35-10 - - Intermittent
16684/P0300/35-00
16685 /P0301/35-00
Readiness: 0110 1101

18032/P1624/35-10
16684 - Random/Multiple Cylinder Misfire Detected P0300 - 35-00 -
16685 - Cylinder 1 P0301 - 35-00 - Misfire Detected
Since then, we replaced the coil #1 (for the second time in two months.

Car ran well for the first few blocks then, as long as the car was under power (i.e. no idle at a stop or coasting when at speed on the highway, car runs well, no flashing engine warning light), but the minute there is an idle or power off, flashing engine warning light, and car is missing again.

Last night, just to rule the sparkplug out, we replace plug #1. This morning, with a cold engine, no problems, but the minute the engine is warm, it starts to miss. And get the following scan.

Monday,15,October,2012,11:32:19:36044
VCDS Version: Release 11.11.4
Data version: 20120807
glhglh

Chassis Type: 4B - Audi A6 C5
Scan: 01 02 03 06 08 15 16 17 18 22 34 35 36 37 45 55 56 57 65 67
75 76 77

VIN: WA1YD64B74N013322
-------------------------------------------------------------------------------
Address 01: Engine Labels: 078-907-551-AZA.lbl
Part No: 4Z7 907 551 S
Component: 2.7L V6/5VT G 0010
Coding: 07755
Shop #: WSC 02325
VCID: 53AB78A9A1798480CC7
WA1YD64B74N013322 AUZ7Z0C2415712

2 Faults Found:
16684 - Random/Multiple Cylinder Misfire Detected P0300 - 35-00 -
16685 - Cylinder 1 P0301 - 35-00 - Misfire Detected Readiness: 0010 0001

We have again use the stethoscope to see if we could hear a vacuum leak, but heard nothing out of the ordinary.

We are stumped. Any more ideas?

Prospeeder

Its the powerstages on top of the airbox. try swapping them around and see if the miss changes cylinders

glhglh

We don't understand this.

01 2.7t

I don't think that the 04 will have the powerstages on the top of the airbox, 04 should be the updated set up for the coil packs. However I had a similar problem that haunted me, in my case a compression test found a leaking valve seat. I would say carefully inspect all vacuum lines and if they are ok try a compression test.

Kneale Brownson

Random misfires for me went away with new plugs and coil packs. The techs tell me there have been a couple dozen revisions of the Audi power packs and you need to be careful about which ones you use.

Prospeeder

ohh that is the BEL engine code. So no power stage. I didnt see the lean codes, and maf code also, you have an obvious HUGE intake leak like a blown off boost hose. If not, the MAF could be bad, try unplugging it and run the car and see how it does.

glhglh

With the MAF unplugged, do i dare make a 40 mile test?

Or just a few blocks.

Prospeeder

remember too when diagnosing, that the misfires are a result of the Lean condition, its running so lean that its misfiring. You need to find why its lean, Large air leaks, bad input from sensors (MAF mostly), Low fuel supply or pressure.

glhglh

when we disconnected the MAF, it ran without missing, but only for about 5 minutes. then much worse.

GTA_Driver

You could try replacing your coolant temp sensor, a $20 part.