1996 B5 A4 2.8V 12V AFC auto

Engine noise (resembling a diesel engine) is still very disconcerting.
Only engine code left (EGR code fixed) is a downstream/rear O2 sensor code:

1 Fault Found:
16538 - Oxygen (Lambda) Sensor B2 S1: No Activity
P0154 - 92-00 - Unknown Error Elaboration

It seems to be coming from the front towards driver side. It does NOT sound as if it is coming from the heads/valves.

I also noticed a very pronounced engine vibration occurring at 1500 rpm (maybe 1450 rpm) (with trans in neutral; haven't tried to detect if present also when driving; will report if it occurs with trans in park, standing).

Is that 'normal' or an indicator for something being off/worn/about to fail?

My biggest concern: sign of failing engine internals? Or pulley, waterpump, timing belt tensioner, etc.?

Car has 135k miles (unknown service history), so timing belt job would be recommended soon. But if the internals are soon to fail, I would like to save the time, effort, cost of a timing belt job (obviously).

I bought a cheap stethoscope, will try if that is helpful to locate the source of the noise.

Anything I could try to either rule out certain sources, narrow down the problem, test, document?

Would an uploaded 'sound recording' help?

 

I know you tried to explain yourself very well, but you don't have the code, otherwise I would have to guess it's the Cam tensioner.....but you usually get the code for it.....does it go away with RPMS? Is it worse when it's warmed up or cold?

 

Does a cam tensioner throw a code? If there is a sensor for that, can VAGcom pull a value for it?

It sounds worse when engine is cold.

 

tensioner would throw a 16395 code. However, tensioner is in the BACK of the engine and if you're going to do that, you might as well do the timing belt, water pump, thermostat in the front etc...because you'll be pulling the whole top of engine off...

I'm assuming the noise doesn't stop? and as a friend of mine once said, 'it sounds worse than a diesel...' since you said it's NOT coming from the HEADS, you think, I'm still guessing it's the tensioner or low oil pressure... If you have a registered version of Ross-Tech, run a full scan of DTCs.... if you're using a laptop with a USB interface, have POWER to the laptop, otherwise it will have the 'communication failure' on some modules since there's not enough power to scan those modules with USB when unplugged.

It also could be low oil pressure, oil pump, clogged oil pick up valve. I'm also going to assume your check engine light is on correct? Any other lights/CELLS??

Basically it's worse when it's cold because the oil isn't warmed up and circulating yet...low oil pressure....loose/worn out cam tensioner....

Does the noise EVER go away AT ALL? Listen to the noise VERY carefully with your stethascope, and see if it sounds like a loose chain banging against the cover in the back, it seems like it's coming from the front, but make sure it's not coming from the back....like on a bike or a chain saw....

If you're mechanically inclined, have lots of time and patience, theres some good write ups on how to do the cam tensioner, timing belt etc...

Before you go doing the tensioner/timing belt, if your mechanically inclined, search for the DIY oil pump pick up valve threads-and read them....then I would drain oil, pull off oil pan, and check, replace oil pump and pick up valve, look at the screen in there and see if its clogged....BEFORE you EVEN do that, messure the oil pressure.....is the oil light on? When was your last oil change?

I'd be hesitant to drive it though with that noise...

Last option, or first, if there's a stealership around, or good audi mechanic, have them give you a FREE estimate or what they think it is, and walk away... ;-) Or look on here on the VAG COM thread, see if there's someone in your area that works on Audis that's on this thread....

As far as the P0154, here's what I googled for you:

Fault Code Definition
Code P0154 is triggered when the Oxygen Sensor signal that is sent to the Power Train Control Module remains at or near the .450 set voltage point.

Symptoms

Check Engine Light will illuminate

In many cases, no abnormal symptoms may be noticed
In some cases, the engine may hesitate during acceleration
Poor fuel economy
Common Problems That Trigger the P0154 Code

Defective Oxygen Sensor
Faulty Oxygen Sensor wiring or connections
Missing Oxygen Sensor Heater Circuit Power Voltage

Common Misdiagnoses

Oxygen Sensor is replaced when the real problem is a vacuum leak
Oxygen Sensor is replaced when real problem is a poor connection

 

Also, when WAS teh timing belt etc last done?

Here's another write up I found that might help you that I googled for you-read the whole answer...now I have to go to work.... joy joy joy...

http://www.justanswer.com/audi/2o6lb...mp-timing.html

 

marcymark, thanks for the good tips.


Only one (downstream O2 sensor) code left (last one I was fighting was blocked EGR passage; done).

Noise loudest when cold and lower RPM, never goes away entirely.
Seems to be more pronounced under load (vs. free revving).

Stethoscope trial today (never used one, so I am not sure if I will find anything).
Trying to get audio file small enough to upload.

Additional noise is coming from a slight leak at one of the exhaust flex pipes.

Good point to get the serpentine belt off to eliminate some of the secondary elements. What is driven off the belt?

No documented service history. Timing belt could be never, but more likely at 60-80k (now 132k). So it is due and potentially worn (stretched?).

Never dealt with the secondary air pump (what is it for? some smog stuff?). Cruise control not working. Would pump problem show up in VAGcom?

Here is the most recent log. Airbags, HVAC, downstream O2 sensor (on its way).

VCDS Version: Release 10.6.3
Data version: 20101206

Monday,07,March,2011,13:01:09:22662

Chassis Type: 8D - Audi A4 B5
Scan: 01 02 03 08 15 16 17 25 35 37 45 55 56 57 67 75 76 77

Mileage: 213130km/132432miles
-------------------------------------------------------------------------------
Address 01: Engine Labels: None
Part No: 8D0 906 266 B
Component: 2,8l V6/2V MPI OBD2 D01
Coding: 01251
Shop #: WSC 06325
VCID: 2B5BF371F383

1 Fault Found:
16538 - Oxygen (Lambda) Sensor B2 S1: No Activity
P0154 - 92-00 - Unknown Error Elaboration
Readiness: N/A

-------------------------------------------------------------------------------
Address 02: Auto Trans Labels: 01V-927-156.lbl
Part No: 8D0 927 156 J
Component: AG5 01V 2.8l2V US D89
Coding: 00000
Shop #: WSC 00000
VCID: 3469E80D2EBD

No fault code found.

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 4D0-907-379-ABS.lbl
Part No: 4D0 907 379 J
Component: ABS/EDS BOSCH 5 7679
Shop #: BB 37679
VCID: 356FD50925C7

No fault code found.

-------------------------------------------------------------------------------
Address 08: Auto HVAC Labels: 8L0-820-043-2D.lbl
Part No: 8L0 820 043 D
Component: A4 KLIMAVOLLAUTOMAT_D75
Coding: 04162
Shop #: WSC 06325
VCID: 29570979F97F

5 Faults Found:
00792 - A/C Pressure Switch (F129)
31-00 - Open or Short to Ground
01297 - Sensor for Vent Temperature; Footwell (G192)
30-00 - Open or Short to Plus
01296 - Sensor for Vent Temperature; Center (G191)
30-00 - Open or Short to Plus
01206 - Signal for Duration of Ignition Off Time
27-10 - Implausible Signal - Intermittent
01582 - Signal for Coolant Temperature
30-00 - Open or Short to Plus

-------------------------------------------------------------------------------
Address 15: Airbags Labels: 8A0-959-655.lbl
Part No: 8A0 959 655 D
Component: Airbag V AUDI D00
Coding: 00127
Shop #: WSC 06334
VCID: 3469E80D2EBD

4 Faults Found:
65535 - Internal Control Module Memory Error
00-10 - - - Intermittent
00532 - Supply Voltage B+
07-10 - Signal too Low - Intermittent
00588 - Airbag Igniter; Driver Side (N95)
32-10 - Resistance too High - Intermittent
01025 - Trigger for On Board Diagnostic Lamp; Malfunction
31-10 - Open or Short to Ground - Intermittent

-------------------------------------------------------------------------------
Address 17: Instruments Labels: 8D0-919-0xx-17.lbl
Part No: 8D0 919 035 G
Component: B5-KOMBIINSTRUMENT D08
Coding: 00262
Shop #: WSC 02032
VCID: 2E5DFA65C091

No fault code found.

End ---------------------------------------------------------------------

 

Oil changed 1000 miles ago.
If sludge or oil pickup issue, would it show on oil pressure?
How can I measure oil pressure? Where to tap in?

Is it difficult to take the drive belt off?

As I said: biggest concern is that the noise indicates a failing main bearing ('spun bearing'), i.e. engine shot and need for new engine. Then, any investment in time and money is fruitless. If not, I'm am happy to continue 'investing' by complete de-sludge (incl. oil pump; how much is material cost for the job?), timing belt.

Done so far (engine):
- new plugs
- new injector O-rings
- new air filter
- oil and filter change 1k mls ago
- new radiator and fluid
- new vac lines
- cleaned TB, EGR and blocked EGR passage
- flex pipes welded in (previous owner hack job welding solid pipe in poorly)

Remaining:
- replace downstream O2 sensor (coming this week)
- still some perceived hissing noise coming from back of TB ('phone wire fix'?). Vac at idle is -19.
- tiny oil leak on passenger side, seams to be bottom of valve cover; barely wet, but smell when engine hot
- quiet exhaust leak at new passenger side flex pipe
- cruise control not working
- perceived lack of power (not validated with acceleration data)
- engine shudder at 1480 rpm in neutral/park. Could it be the trans/torque converter (complete trans replaced)

 

Yesterday, took recorded some video. 3 files recorded with when engine was cold, 1 file when engine was warm.

The 'diesel' sound is less pronounced when warm. I still have not 'located' where the sound is coming from; I would still say front driver side.

Comments, suggestions are welcome.

I plan to take the drive belt off in the next days to eliminate some of the aux systems (with their pulleys, bearings, etc.).
Also will try the stethoscope.

Cold 1:
http://s853.photobucket.com/albums/a...t=MVI_5615.mp4

Cold2:
http://s853.photobucket.com/albums/a...t=MVI_5616.mp4

Cold3:
http://s853.photobucket.com/albums/a...t=MVI_5617.mp4

Warm1:
http://s853.photobucket.com/albums/a...t=MVI_5619.mp4

 

Stethoscope did not reveal much.
Took the drive belt off, no change.

Opened up the timing belt covers a bit. Both belts can be pushed in without force by about 20mm. Will upload short video later.

Is that 'normal'?
Or is that an indication that the timing belt is stretched and/or the timing belt tensioner is not tensioning the belt enough anymore (weak or at the end of its travel)?

If not normal, could the sloppy belts be the source of the noise?

 

Here are the 2 short videos. Pushing the screw driver down on the drive belt, no force. Estimate: 20mm.

Passenger Side:
http://s853.photobucket.com/albums/a...t=MVI_5625.mp4

Driver Side:
http://s853.photobucket.com/albums/a...t=MVI_5623.mp4