New to me D2 4.2 2000 A8: Misfire, rat poop airbox, water in ecu box.
 

Hi, Thanks for taking the time to help me figure this seemingly common Misfire problem. The little sleeper is a 1 owner with a new fuel filter good pump, clean air filter, good looking belts.
The Bad: When I unplugged maf I found rat poop(not much maybe 1/8 of a fun size snickers) in the air box, I am assuming urea had affected and oxidized maf and temp sensor, so I cleaned it with CRC maf cleaner but that could just be pointless as it's micron thin coated sensor just may be toast? I also peeked in the ecu box which was missing a screw back right allowing drips in grr I know its tough to get too but jeez!.. Cleaned and dryed that box up took off all 3 cables in ecu compartment observed pins were shiny couple had very light green look so I sprayed electrical cleaner dispersant lube waited to dry and very carefully re-attached. I also found rust running from 7-11 inches up the dipstick. I will try to do a compression test today. My #1 thought after having dealt with water damaged cell phone board, is that the ecu is not protected from humidity and the board probably has oxidized to a certain point.
I did do 2x VAGCOM for this and for run #1 had the Maf/temp sensor unplugged, I did do a log and the log reported temp as 48 C which is 122 F and it is only 40 F here!
RUN 1
Chassis Type: 4D (4D - Audi A8 D2 (1994 > 2003))
Scan: 25 01 03 08 11 15 16 17 18 35 37 45 55 56 57 65 67 75 76 77
02

VIN: WAUFL5
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Address 01: Engine Labels: None
Part No: 4D0 907 559
Component: 4.2L V8/5V G 0006
Coding: 06753


14 Faults Found:
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 -
16692 - Cylinder 8
P0308 - 35-00 - Misfire Detected
16690 - Cylinder 6
P0306 - 35-00 - Misfire Detected
16687 - Cylinder 3
P0303 - 35-00 - Misfire Detected
16691 - Cylinder 7
P0307 - 35-10 - Misfire Detected - Intermittent
16689 - Cylinder 5
P0305 - 35-00 - Misfire Detected
16688 - Cylinder 4
P0304 - 35-00 - Misfire Detected
17551 - Load Calculation Cross Check
P1143 - 35-10 - Upper Limit Exceeded - Intermittent
18010 - Power Supply Terminal 30
P1602 - 35-10 - Voltage too Low - Intermittent
16497 - Intake Air Temp. Sensor (G42)
P0113 - 35-00 - Signal too High
16486 - Mass Air Flow Sensor (G70)
P0102 - 35-00 - Signal too Low
17539 - Oxygen (Lambda) Sensor; B2 S1
P1131 - 35-00 - Internal Resistance too High
17521 - Oxygen (Lambda) Sensor; B1 S1
P1113 - 35-00 - Internal Resistance too High
16685 - Cylinder 1
P0301 - 35-00 - Misfire Detected
Readiness: 0110 1101

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Address 03: ABS Brakes Labels: 8D0-907-389.lbl
Part No: 4D0 907 389 E
Component: ABS/ESP allrad D26
Coding: 08397
Shop #: WSC 20209
VCID: 3169F295FB2DCFC264-5140

1 Fault Found:
18265 - Load Signal
P1857 - 35-00 - Error Message from ECU

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Address 08: Auto HVAC Labels: 4D0-820-043-MYX.lbl
Part No: 4D0 820 043 Q
Component: A8-Klimavollautomat D12
Coding: 00180
Shop #: WSC 02312
VCID: 2A5BE5F9D6FBBC1AA5-257A

4 Faults Found:
00711 - Left Footwell Flap Positioning Motor (V108)
41-10 - Blocked or No Voltage - Intermittent
01274 - Air Flow Flap Positioning Motor (V71)
41-10 - Blocked or No Voltage - Intermittent
00604 - Potentiometer Positioning Motor for Air Flow Flap (G113)
30-10 - Open or Short to Plus - Intermittent
01592 - Air Quality Sensor (G238)
57-10 - Electric Circuit Failure - Intermittent

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Address 15: Airbags Labels: 4D0-959-655-AI8.lbl
Part No: 4D0 959 655 R
Component: Airbag Front+Kopf 5004
Coding: 00427
Shop #: WSC 20209
VCID: 4189A2554B8D5F4294-5122

1 Fault Found:
00532 - Supply Voltage B+
07-10 - Signal too Low - Intermittent

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Address 16: Steering wheel Labels: 4B0-907-487.lbl
Part No: 4B0 907 487
Component: E Lenkrad Elektronik D03
VCID: 69D95AF5137D77026C-4B7E

No fault code found.

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Address 17: Instruments Labels: 4D0-919-033-MYX.lbl
Part No: 4D0 919 035 AL
Component: D2-KOMBIINSTR. VDO D26
Coding: 02283
Shop #: WSC 02314
VCID: 70EF379130A786CA2B-5140
WAUFL54DXYN009005 AUZ7Z0X1203817

1 Fault Found:
00668 - Supply Voltage Terminal 30
53-10 - Supply Voltage Too Low - Intermittent

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Address 35: Centr. Locks Labels:. 8D0-862-257.lbl
Part No: 8L0 862 257 N
Component: CV-Pump D11
Coding: 16140
Shop #: WSC 02314
VCID: 408FA7514087564A9B-4EB2

16 Faults Found:
01367 - Central Locking Pump Run Time Exceeded (Likely Leak)
35-00 - -
01371 - Alarm triggered by Door Contact Switch; Driver's Side
35-00 - -
01372 - Alarm triggered by Door Contact Switch; Rear Passenger Side
35-00 - -
01374 - Alarm triggered by Terminal 15
35-00 - -
01370 - Alarm triggered by Interior Monitoring
35-00 - -
01369 - Alarm triggered by Hood Switch
35-00 - -
01368 - Alarm triggered by Luggage Compartment Switch
35-00 - -
01362 - Close Switch for Tailgate/Trunk (F124)
29-00 - Short to Ground
01389 - Tailgate Open Switch (F124)
29-00 - Short to Ground
01571 - Signal for Seat Memory
29-00 - Short to Ground
00000 - End of output
00-00 - -
00991 - Interior Lights
28-00 - Short to Plus
00955 - Key 1
09-00 - Adaptation Limit Surpassed
00956 - Key 2
09-00 - Adaptation Limit Surpassed
00957 - Key 3
09-00 - Adaptation Limit Surpassed
00958 - Key 4
09-00 - Adaptation Limit Surpassed

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Address 45: Inter. Monitor Labels: 4B0-951-178.lbl
Part No: 4D0 951 177 B
Component: Innenraumueberw. D05
Coding: 00001
Shop #: WSC 00000
VCID: 285F1FF1C8F78E0AB3-522E

3 Faults Found:
01349 - Alarm via Theft Warning System; Front
35-00 - -
01350 - Alarm via Theft Warning System; Rear
35-00 - -
01462 - Anti-theft alarm ultra sonic Sensor (G209)
53-10 - Supply Voltage Too Low - Intermittent

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Address 55: Headlight Range Labels: 4B0-907-357-DYN.lbl
Part No: 4B0 907 357 C
Component: dynamische LWR D02
Coding: 00001
Shop #: WSC 131071
VCID: 285F1FF1C8F78E0AB3-4B64

No fault code found.

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Address 56: Radio Labels: 8D0-035-1xx-56.lbl
Part No: 4D0 035 195 A
Component: Radio D00
Coding: 16833
Shop #: WSC 99203
VCID: 204F07D1A0C7764AFB-4AE8

1 Fault Found:
01044 - Control Module Incorrectly Coded
35-00 - -

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Address 02: Auto Trans Labels: 01L-927-156.lbl
Part No: 4D0 927 156 CP
Component: AG5 01L 4.2l5V USA 1414
Coding: 00002
Shop #: WSC 02314
VCID: 79F90AB563DDC7829C-5140

2 Faults Found:
18265 - Load Signal
P1857 - 35-00 - Error Message from ECU
18243 - Pressure Control Valve 5 (N233)
P1835 - 35-00 - Short to Plus

End-------------------------(Elapsed Time: 04:43)--------------------------

Now with Maff plugged in after cleaning:
12 Faults Found:
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 -
16692 - Cylinder 8
P0308 - 35-10 - Misfire Detected - Intermittent
16690 - Cylinder 6
P0306 - 35-10 - Misfire Detected - Intermittent
16687 - Cylinder 3
P0303 - 35-00 - Misfire Detected
16691 - Cylinder 7
P0307 - 35-10 - Misfire Detected - Intermittent
16689 - Cylinder 5
P0305 - 35-10 - Misfire Detected - Intermittent
16688 - Cylinder 4
P0304 - 35-10 - Misfire Detected - Intermittent
17551 - Load Calculation Cross Check
P1143 - 35-10 - Upper Limit Exceeded - Intermittent
18010 - Power Supply Terminal 30
P1602 - 35-10 - Voltage too Low - Intermittent
16497 - Intake Air Temp. Sensor (G42)
P0113 - 35-10 - Signal too High - Intermittent
16486 - Mass Air Flow Sensor (G70)
P0102 - 35-00 - Signal too Low
18032 - MIL Request Signal Active (Check TCM for errors too!)
P1624 - 35-00 -
Readiness: 0110 1101

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Might add that it it seemed to run better without MAF hooked up, when I plugged the MAF back and stepped on the gas it would bog before stumbling to accelerate engine a bit.

Might throw a fuel pump relay at it, seems cheap enough a test.

Hmm... Seems to idle smoother with maf plugged in but not accelerate, bogs then slight blip if it does not die...

With the Maf unhooked engine accelerates as per pedal request no hesitation.

It's been mothballed broken for how long? I'm assuming you cleared all the old codes and the only ones that come back are all the ones in you last list, multiple misfires, etc? Low voltage to the ECU intermittent...how's your battery? What voltage are you seeing into the ECU. The cowl area floods easily if the drains clog with leaves, etc, then water gets into the Engine Electronics Box from below, and the ECU goes for a swim, creating funky short circuits and weird error codes, like alarms at every door, hood, trunk, motion sensor. You might want to remove the four screws and see how the ECU board looks. Green stuff on the board could be leaking capacitors or corrosion from water.

You might try car-parts.com for a cheap used MAF. Rodents like to chew wires, so I'd inspect the MAF and IAT wiring. That last error mentions checking the TCU as well. Guessing you'll find a bunch of weird codes there as a result of the TCU brain getiing wet as well. It looks the same size and location as the ECU in the underhood electronics box. Read them, save them (if you want) and clear them. Then see which ones, if any come back.

If the ECU is toast, you can get a used one cheap from car-parts.com or a local wrecker. Usually around $50. The trick is, you have to pair it to the car. The Instrument clustedr is the keeper of the immobilizer system. You need the 4 digit pin from the Immobilizer. Enter that pin into VAG COM, and then you can pair the new used ECU to the car.

Can you datalog the MAF output with VAG COM. I'm sure you can, but have never tried it myself. Datalog the voltage into the ECU, the IAT sensor output & the MAF. Scratch you head a little, what doesn't make sense, and figure which part or related wiring is at fault or...all of them. Once you've got those errors dealt with, then you can trust all of the other components to chase the misfires. Low voltage to the ECU, bad MAF or bad IAT signal (or bad ECU) could cause poor running and misfires as a symptom

Once that is dealt with: Plugs, Injectors and coils. At a certain age and mileage the original coils do die. But you could have corrosion on spark plug tips for all we know. Move coils around and see if faults move or stay in the same place. If they move - bad coil, if they don't bad plug, injector or compression. Later Red top coils for ...uhmm.... the 2.0T ... among others are a superior coil, cheaper and a little longer. If you get to that point, buy one as a spare to test fit. The ones I got are plug and play, but some are wired differently. But this is only after you figure out the MAF IAT & ECU goings on. Last but not least, a dying fuel pump becomes annoyingly intermittent, but you said yours was good.

I had signs of mouse excrement in my '97 after sitting for 5 years, and both Power Output Stages that trigger the coils had some cylinders dead.

Thanks, that all sounds like good advice!..I did not clear the old codes so I did that yesterday and I did the maf test on channel 32..
lamda was 0 so that is fried, another on the way 8$ on ebay!
once I cleared the codes I ran it for a bit and only got :
7 Faults Found:

18032 - MIL Request Signal Active (Check TCM for errors too!)
P1624 - 35-00 -
16486 - Mass Air Flow Sensor (G70)
P0102 - 35-00 - Signal too Low
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 -
16688 - Cylinder 4
P0304 - 35-00 - Misfire Detected
16687 - Cylinder 3
P0303 - 35-00 - Misfire Detected
17539 - Oxygen (Lambda) Sensor; B2 S1
P1131 - 35-00 - Internal Resistance too High
16686 - Cylinder 2
P0302 - 35-00 - Misfire Detected

Readiness: 0110 1101

I THEN CLEARED AGAIN AND RAN FOR A COUPLE MINS! :
1 Fault Found:
18048 - Internal Control Module
P1640 - 35-00 - EEPROM Error
Readiness: 0110 1101

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Address 03: ABS Brakes Labels: 8D0-907-389.lbl
Part No: 4D0 907 389 E
Component: ABS/ESP allrad D26
Coding: 08397
Shop #: WSC 20209
VCID: 3169F295FB2

1 Fault Found:
18265 - Load Signal
P1857 - 35-10 - Error Message from ECU - Intermittent

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Address 08: Auto HVAC Labels: 4D0-820-043-MYX.lbl
Part No: 4D0 820 043 Q
Component: A8-Klimavollautomat D12

Looks like it is a very responsible computer, blaming itself now; although we know where the blame really lays VW bean counters!!

I did charge the battery still low power, going to try the relay's today 645 (autozone rl44) and the big grey fuel pump one #372

I will then progress to power in test, a certain pin to test? Thanks for all your help!

oops I guess not low power that code cleared, just EEprom..I would rather re-use this thing if it is just writing a bios Vag com cannot do that?

Eh nevermind found a immo delete one for 60$ Now to build a better waterproof ecu box!!