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TDiQ 170 weird power loss, and today - scraping noise when clutch is released

Discussion in 'Audi S4/A4/A4 Cab (B7 Chassis)' started by Lafarge, Feb 5, 2014.

  1. Lafarge
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    Lafarge New Member

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    [Feb 5, 2014]
    Hi folks. thanks for reading :/

    Bought my '56 TDiQ 170 a couple of months back, seemed to be a good enough motor until the last week or two. Couple of times it's lost power while driving, both times it's been wet with lots of standing water on the roads - which I avoid if I can - so I don't know if that's relevant.

    A couple of weeks back, 15 minutes into my commute home, really heavy rain on the M25, loads of spray, it started to lose power - just felt like it had dropped a cylinder, and struggled to get past 2000 RPM unless I absolutely floored it, but even then you could tell something wasn't happy.

    Today, on the M4, an hour into my commute to work it began to lose power, same symptoms, but this time I could worryingly hear a scraping noise coming from the engine bay - at least that's where it sounded like it was coming from - much like the sound of a brake pad scraping on a disc. Press the clutch, noise goes away, engine revs freely in neutral. Engage a gear, noise is there and increases in volume as you apply engine load with the throttle. Just coming onto the M4 slip from the M25, I thought my exhaust had gone, as it was suddenly really boomy when the revs went from idle to about 1100 - blip the throttle, boom. Really weird :/

    I know it's a long shot, and I know I need to get the fault codes read (presuming there are some but does this ring bells with anyone?. There are no warning lights, no increase or decrease in temperature, no whistles or bangs. The only other thing I've noticed is that when parked, if you pull away slowly on full lock, to manoeuvre in a car park etc, there's a juddering/vibration through all 4 wheels - but it's only momentary as you go from being still, to setting off, so I guess it's just the haldex sorting itself out? Again, maybe (hopefully!!) a red herring.

    Car had an oil and oil filter change at Audi a month ago, I just fitted a new air filter and fuel filter, which has dramatically improved the responsiveness and MPG (as you would expect). I don't thrash it, but I do put my foot down every so often. Always sit at the speed limit or thereabouts, on motorways with cruise engaged. It's had the injector recall but I don't know whether it was all 4, and/or the loom - will call Audi shortly.

    Any thoughts, very welcome...

    Thanks,

    Rich
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  3. MartayMcFly
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    MartayMcFly Well-Known Member Regional Rep VCDS Map User

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    [Feb 5, 2014]
    Um... TDi RS? Might need to get this moved into the A/S4 B7 section, not this B5/B7 RS4 one.

    Juddering sounds like a haldex issue, though I'm not sure if that'd somehow restrict the power too. Seems like there might just be a few things needing looked at. Boomy exhaust and scraping noise from the engine bay sounds like it's an expensive fix too, unfortunately.
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  4. PetrolDave
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    PetrolDave Well-Known Member

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    [Feb 5, 2014]
    This is definitely in the wrong forum as Audi have never made an RS diesel.

    Having said that, if it's an A4 quattro then it's Torsen not Haldex (only transverse engined quattros have Haldex).
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  5. Lafarge
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    Lafarge New Member

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    [Feb 7, 2014]
    It's a B7 A4 TDiQ 170...so hopefully this is the right place - apologies if it wasn't originally...

    So, driving to and from Cambridge a couple of nights ago, didn't miss a beat. Roads were dry, no juddering or noises, no power loss. Really good responsive drive, enjoyed every minute.

    Drove home yesterday afternoon in the rain (6.30pm, M4 and M25) and it started playing up again. Got home and the exhaust fumes absolutely stank - burning rubber is the closest thing I can describe it as. Really unpleasant.

    Checked the water level in the radiator fill reservoir this morning, the level is fine, but the water is filthy and orange/rust coloured, so probably overdue a change.

    Had the ScanGaugeII I've borrowed connected to the car this morning, everything seems fine on the default gauge readings, boost is good which is a relief, but the water temp showed as high as 97 degrees C while I was crawling along the M25/M4 this morning (60 minutes to do less than a mile...) while the car read a solid 89/90 degrees the whole time. Didn't hear the fan come on either so I'm wondering if I have a stuck thermostat or maybe the EGR isn't opening/closing. Could explain why it's running hot and down on power?

    Interestingly, no fault codes were detected, which makes me think it's something physical/mechanical instead of something logical. Doesn't explain why it boomed as I blipped the throttle (sounded like the boom was going through the exhaust) from idle to 1,000/1,100 RPM.

    The scraping noise is still there, it's there all the time (when it's playing up as described here) but as the clutch is pressed the revs drop which made me think the noise was related to the clutch, but it's there all the time. Not high pitched like metal on metal, more like a plastic undertray being dragged along the road (yes, I've checked ;) !!!!!).

    I have new gaskets for the EGR so I'll hopefully pull that off at the weekend and check it's clean/operational.

    Anyone ever heard or seen anything like this? :/

    Thanks,

    Rich
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  6. Lafarge
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    Lafarge New Member

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    [Feb 8, 2014]
    More of the same yesterday, no fault codes, water went up to 97 degrees C. What I think is the FMIC temp shows as 20 degrees C, when the external temp outside is between 7 and 10 degrees C. Still no P codes being generated...

    Anyone have any ideas?? Hoping the rain will stop long enough so I can pull the EGR off in a bit...
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  7. Lafarge
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    Lafarge New Member

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    [Feb 9, 2014]
    So, pulled the EGR off today and it was really clean - had a tiny bit of gunk but barely anything. Looked inside the manifold and it looks ok, but would clearly benefit from a clean. The EGR has what looks like a date stamp across the bottom of the motor housing, that reads 40640/0049/250912/00012 - I'm guessing 250912 is the date stamp. The body of the EGR is really clean, the motor mechanism works perfectly, it's shut by default, and the cogs open it fully and easily if moved by hand. So it seems the EGR is working properly. Oh and it's a Siemens VDO unit with VWAG stamped on it, p/n seems to be 03G 131501 R, made in CZ. Seems legit...

    The only weird thing I noticed was the electrical connector that plugs into the EGR has a twin which isn't connected to anything. Can't see anything for it to plug into either. Reading the "Another 2.0 TDi EGR valve cleaning" thread there is mention of two plugs being plugged in. Wonder if I've had the EGR replaced before I got the car and it's maybe not the right EGR? Just seems odd to have a plug laying around doing nothing in the engine bay.

    Hasn't made any difference to how the car runs, I put new gaskets on when I put the EGR back on too.

    Anyone? Bueller?? Bueller??? Anyone!!!? :)
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  8. Lafarge
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    Lafarge New Member

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    [Feb 11, 2014]
    No-one had similar symptoms?? :/
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  9. Lafarge
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    Lafarge New Member

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    [Feb 17, 2014]
    Really surprised no-one has had similar symptoms.

    Thanks for all the replies though!!!
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