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#1
6th December 2012, 05:59 PM
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Thump when slowing down
Hi Guys and Gals,
my apologies for being wrapped up in my little world almost exclusively of late. My 3.7 FL 40v has developed a thump coming from the trans when slowing down normally, I also seem to have fluctuating tickover. I have read somehere that the thump is caused by the MAF sensor, is this correct? Something to do with it sending the wrong signal to the Torque Converter? Could any of you Gurus out there shed some light on this? As I won't drive the car until I have effected a cure. Thanks in anticipation, Steve Last edited by Trophy885; 6th December 2012 at 06:01 PM. Reason: spelling correction 
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#2
6th December 2012, 06:21 PM
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Quote:
Have you tried a VAGcom scan? MAF errors normally show up so at least that would be a starting point
__________________
Confidence is the feeling you have before you know better . . . .  Audi A8 D2 3.7 Quattro Sport 1999 FL - Melange 2nd Place Winner - A8-Freunde Annual German Meet 2012 at Edersee 20" x 9" Bentley GTC Wheels with 385mm W12 Front Discs & Bentley Caliper Covers, Front Lowered on Coilovers, Xenons, Combined DRLs and LED Foglights to modified OEM front fog lamp position, Alcantara/Leather, Full Black Alcantara headlining + pillars and blind shelf, Bespoke Flat Bottomed Sports Steering Wheel, Dark Myrtle Wood, Autodim Mirrors, Bose, Blinds, Digital TV, Ski Hatch, Modified rear exhaust section for extra V8 Burble  Audi S8 D2 Final Edition 2002, Avus Silver with Red Leather Interior Tiptronic with Sport mode button, Sony rear entertainment package, Bose sound system, Audi Navigation Plus, 20 inch Final Edition alloys, Full Cat Back Stainless Milltek exhaust, giving a great V8 burble Audi A8L D2 4.2 Petrol with LPG - Ebony Black Audi A8L D4 FL 4.0T Petrol twin turbo - Havana Black Audi A2 1.6 FSi Sport - Dolphin Grey with Votex body kit and Red Leather Interior and some other A8's A8L's and Mercs
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#3
14th December 2012, 08:19 PM
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Hi Guys and Gals,
I have done vagcom on my poorly blue boy, (though the chauvinists might say HE is really a SHE!) below is an engine read out, I can also hear air (sounds like induction leak) at idle. Also at idl;e there is the faintest hum of fuel pump, which makes me think I have acombination of problems, possibly a perished hose, and a fuel pump on the edge of dying. Your thoughts, as always are appreciated! 16514 - Oxygen (Lambda) Sensor B1 S1 P0130 - 35-10 - Malfunction in Circuit - Intermittent 17536 - Fuel Trim; Bank 1 (Mult) P1128 - 35-10 - System too Lean - Intermittent 17538 - Fuel Trim; Bank 2 (Mult) P1130 - 35-10 - System too Lean - Intermittent 17544 - Fuel Trim: Bank 1 (Add) P1136 - 35-10 - System too Lean - Intermittent 17546 - Fuel Trim: Bank 2 (Add) P1138 - 35-10 - System too Lean - Intermittent 17549 - Load Calculation Cross Check P1141 - 35-10 - Implausible Value - Intermittent Readiness: 0000 0000 Best Regards to all, Steve
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#4
14th December 2012, 08:38 PM
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Could be Oxygen Sensors or MAF steve - for example
17536/P1128/004392 - Fuel Trim; Bank 1 (Mult): System too Lean Possible Symptoms Malfunction Indicator Light (MIL) active Possible Causes Mass Air Flow (MAF) Sensor faulty Oxygen Sensor Control faulty Oxygen Sensor(s) faulty Fuel Injector(s) faulty Possible Solutions Check Mass Air Flow (MAF) Sensor Check Oxygen Sensor Control Check Oxygen Sensor(s) Check Fuel Injector(s)
__________________
Confidence is the feeling you have before you know better . . . . Audi A8 D2 3.7 Quattro Sport 1999 FL - Melange 2nd Place Winner - A8-Freunde Annual German Meet 2012 at Edersee 20" x 9" Bentley GTC Wheels with 385mm W12 Front Discs & Bentley Caliper Covers, Front Lowered on Coilovers, Xenons, Combined DRLs and LED Foglights to modified OEM front fog lamp position, Alcantara/Leather, Full Black Alcantara headlining + pillars and blind shelf, Bespoke Flat Bottomed Sports Steering Wheel, Dark Myrtle Wood, Autodim Mirrors, Bose, Blinds, Digital TV, Ski Hatch, Modified rear exhaust section for extra V8 Burble Audi S8 D2 Final Edition 2002, Avus Silver with Red Leather Interior Tiptronic with Sport mode button, Sony rear entertainment package, Bose sound system, Audi Navigation Plus, 20 inch Final Edition alloys, Full Cat Back Stainless Milltek exhaust, giving a great V8 burble Audi A8L D2 4.2 Petrol with LPG - Ebony Black Audi A8L D4 FL 4.0T Petrol twin turbo - Havana Black Audi A2 1.6 FSi Sport - Dolphin Grey with Votex body kit and Red Leather Interior and some other A8's A8L's and Mercs
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#5
15th December 2012, 12:51 AM
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Hi Neil,
thanks for that, informative, but, NO MIL light on, symptom is engine running lumpy,(sorry, forgot to mention that) not as responsive from idle so, idle, foot down, pause and then revs, with a large amount of hissing. I'm fairly sure I have some split vacuum hoses, which would also probably fit the majority of symptoms, mix weak, on both banks, O2 sensor actually reading correctly as the mix is lean due to the ingress of air. Will try this first, as replacing the vacuum hoses was high on the hit list anyway! Will report back when time allows me the opportunity of swapping the hoses. Many thanks to all. Best regards, Steve
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#6
15th December 2012, 06:58 AM
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The MIL light is only a possible symptom, its possible to have a duff sensor with no light showing.
The light will only come on once the sensor starts giving readings outside the expected range. A faulty sensor can still give readings within range but the wrong readings which could result in fuelling issues. For example on a cold day, it could tell the ECU that its warmer and the result could be lean running
__________________
Manny 2004 A4 1.8T Sport Cabriolet, 89K Miles Past 2004 D3 A8 3.7 Quattro, Xenon, Bose, Blinds, Solar Sunroof, TV, ACC, phone and almost every option. 168K miles rising slowly with retrofit AMI and DVB-T in place of Analogue 2003 Volvo S60 D5 SE Manual, 197K miles. 2001 D2 A8 3.7 QS, Bi-Xenon, Bose, Blinds, Electric Everything, retrofitted RNS-D, 191K Miles
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#8
15th December 2012, 09:28 AM
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Thanks mannyo and psyche,
TBH, the vacuum pipe replacement was so "up there" on the list of things to do, that that roll of replacement pipe is actually in the boot!! Hoping for some spare time through the festivities to get a go at it. Many thanks one and all. Best regards, Steve
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#9
30th December 2012, 12:33 PM
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Hi Guys and Gals,
I'm pleased to report the "thump" has now disappeared, after I replaced the small vacuum lines, and removed the PCV through which I cpould hear was an air leak, subnsequent dissembly revealed a diaphragm in two halves, so two questions, does anyone have a spare?? I don't want to go to the stealers, as the valve is £74!!!! Failing that I will be in contact with our sponsors, fine body of men they are!! Later on, I may try a repair to the diaphragm, possibly bonding a condom to the existing halves, as it is an all but circular split. I have seen this repair before on motorcycle CV carb diaphragms. I suppose the moral of the tale is, before you spend big dollars, have a check around using some old fashioned nouse! Best regards to all. Steve
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#10
3rd January 2013, 07:51 PM
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Hi Guys and Gals,
further to this, the intake is now plugged, and I'm awaiting delivery of the new valve. I have done a vagcom scan, and I'm free of DTCs!!!(Hooray!!!) Interestingly, using vagcat online, I obtained the part No for the valve, and asked TPS, this reduced the rate to £54+ VAT, I then googled it, and was astonished to find that AMAZON could supply it, from the USA, at £49 inc VAT and delivery!! Just thought I'd share....! Best Regards to all Steve
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