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#1
24th February 2016, 12:07 PM
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Stalling when hot
Hi Guys,
Could really do with some help please with my PF 4.2 QS, as I am at a loss of what this could be. My car starts and drives perfectly from cold. As long as I continue driving and cool air is passing through the radiator I do not have any issues. The moment I hit traffic and the cool air decreases through the grill, the car starts to stall. It will start again straight away, but again stalls if I don't start moving. Once underway again the car drivers perfectly. I have had it in the garage and tested or replaced the following with no success Crank case sensor Camshaft sensor Temperature sensor Idle valve cleaned Clasped front hose replaced New air filter, spark plugs. Any help would be greatly appreciated as I am now getting really frustrated with this, to the extent that I am thinking of getting rid of the car. Mileage is 172,000 but still drives perfectly. Thanks David  
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2002 S8 Final Edition, Avus Silver with Red leather interior Guildford, Surrey 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  :1997 A8 Quattro Sport - Now sold when S8 FE purchased 
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#2
24th February 2016, 12:36 PM
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Breather hoses ?
Does the temperature needle actually rise ? Are you sure its an airflow problem, and not just an idling problem ?
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For parts enquiries and Forum User Administration please contact customer services directly, not me  - enquiry@a8parts.co.uk, www.a8parts.co.uk, or call 01642 783537The Daily Town Car - 2023 Tesla Model Y Performance. Black with Black. Giant ipad screen, huge sunroof, 4 wheel drive, Tow bar, lots of ooomph and made in China, so actually built properly unlike the Californian ones. The Family Wagon - 2018 Tesla Model X. Black, 7 Seats, Towbar, Homelink, Enhanced Auto pilot with Summon and self park, Heated front seats, CCS Charger upgrade, MCU2 Upgrade, Falconwing Doors, Self opening / closing doors, Netflix, Spotify, toys, Air suspension, alcantara roof + lots of other stuff...... The 17 year old Driver Wagon 2015 Skoda Citigo Monte Carlo. Alloys, Power steering, Aircon, Leccy windows, Sat Nav, bluetooth, central locking, cup holders, 59 whole bhp. Million times better than my first car. Well jealous..... The First 20 Audis: 2001 D2 4.2 QS Silver, 1997 D2 S8 Silver, 1999 D2 4.2 Silver, 2002 D2 S8 Dolphin Grey, 2003 C5 RS6 Blue, 1998 D2 S8 Black, 2000 D2 4.2 QS/S8 Ming Blue, 2003 D3 4.2 Ming Blue, 2005 B7 S4 Blue, 2006 D3 3.0 Tdi Black, 1999 D2 4.2 Silver, 2003 D3 4.2 LPG Crystal Blue, 2000 D2 S8 Silver, 2007 3.0 Tdi Q7 Black, 2009 B8 S4 Black, 1998 D2 S8 Agate Grey, 2006 D3 4.2 Tdi Blue, 2006 D3 S8, 2007 Q7 3.0 Tdi, 2006 C6 S6, The Second 20 Audis: 2011 A7 Sline, 2001 A2 1.4 Tdi Black, 2002 A2 1.4 Tdi Silver, 2006 A8 4.2 Tdi Blue, 2007 4.2 Tdi Q7, 2006 S4 Cab Silver, 2010 RS6 Saloon Black  , 2007 TT Roadster, 2010 A8 D4 4.2 Silver, 2006 C6 A6 2.7 Tdi Quattro, 2000 D2 4.2 QS/S8 Ming Blue (again), 2008 Q7 4.2 Black, 2009 C6 RS6 Saloon Daytona Grey, 2001 Fully Loaded A2 Tdi, 2006 Avant S6 Black, 2007 VW Caravelle Exec Black (almost an Audi) 2009 TT Roadster Daytona, 2015 Q7 4.2 tdi lava grey, 2002 GmbH D2 demonstrator, 2006 D3 A8 LWB 4.2 Tdi Black Most Recent Audis: 2001 A2 1.4 Tdi Black, 2007 4.2 FSi Q7 ABT Blue, 2016 S5 Coupe Launch model, 2004 S4 B6 Cabriolet, 2016 Q7 Sline White, 2006 Q7 4.2 FSi Black, 2012 Q7 Sline+ 4.2Tdi White, 2008 Blue Audi S8 Everything Else 1989 Subaru Justy, 1986 Vauxhall Cartlton 2.0 GL, 1985 Vauxhall Carlton 2.2 CDi, 1987 Ford Sierra XR4x4, 1983 Vauxhall Senator, 1985 Vauxhall Senator 3.0i, 1997 Polo Saloon, 1997 Peugeot 306 1.9 TDi, Ford Sierra Sapphire 2000E, 1990 Subaru Justy, 2000 Subaru Impreza, 2000 Subaru Impreza RB5, 1993 Range Rover LSE, 2005 VW Bora, 2003 Skoda Superb, 2003 VW Passat V6 4 Motion, 1996 Peugeot 106, 2000 Range Rover 4.0, 2019 Tesla Model 3 Performance
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#3
24th February 2016, 03:56 PM
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Quote:
If it has a vacuum leak somewhere it may not be able to maintain idle with the torque converter engaged. I would expect it to stumble or idle at lower rpm than normal if this is the case. Try turning off the AC and large electrical consumers to ease the load on the engine slightly and see if that has an effect. When it's cold the fuel enrichment and warm-up routine will often be enough to overcome a vac leak, but problems show as soon as the fuel enrichment is shut off.
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#4
25th February 2016, 05:51 PM
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Hi Guys,
The temp gauge does not rise when stuck in traffic No it does not stall if I knock it into Neutral when stopped in traffic. I changed the idle valve with one from our sponsors. This made no difference. I found that leaving the air-con on permanently helped in keeping the revs slightly higher and the second fan working which avoided stalling, but this no longer works now. Can you tell / show me where the breather pipes are located & are they easily changed? Thanks for your responses David 
__________________
2002 S8 Final Edition, Avus Silver with Red leather interior Guildford, Surrey 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 :1997 A8 Quattro Sport - Now sold when S8 FE purchased
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#5
25th February 2016, 06:39 PM
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Does it have twin throttle body's ? Are they full electronic or cable operated . Any fault codes for fuel trims , short term adding or taking away at idle would be a pointer for air leaks .
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#6
25th February 2016, 07:47 PM
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These are the crankcase breather hoses:
 The front one is easy enough to change. The rear two need the inlet manifold off I think, although you might be able to do it with just removing the throttle body. Also check all the vacuum hoses and connections around the throttle body. Its a mess of pipes back there with the idle valve, brake vacuum suction-jet pump thing etc. Definitely sounds like an air leak.
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#7
2nd March 2016, 11:05 AM
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Thanks guys.
Front breather hose replaced recently. Breather hoses at back of engine on order from Germany. Will replace once they arrive. Hope this solves the stalling problem
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2002 S8 Final Edition, Avus Silver with Red leather interior Guildford, Surrey 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 :1997 A8 Quattro Sport - Now sold when S8 FE purchased
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#8
2nd March 2016, 05:07 PM
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Let's hope the new breather hoses help but if they had a leak you could see it. The pressure difference downstream from throttle valve is little so it would need fairly large breach in hoses and would be definitely visible to affect it. It's more likely that leak is upstream from throttle valve as it has a lot bigger vacuum/pressure difference so even small leak that is hard to notice will have more effect on running in idle. So I would be looking at vacuum hoses, valves, actuators, reservoir if you have one, brake servo and hose to it, seals for manifold, injector o-rings.
If you have VCDS have a look at measuring blocks for engine or maybe somebody else from forum members nearby you could offer help if you do not have VCDS or not sure what to look for in measuring blocks.
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Currently 8less 2011 Q7 S Line 3.0TDI, 2016 Tesla Model S 90D 8 history: 2006 A8 Sport 4.2TDI quattro SOLD, 1997 S8, reached end of life with gearbox failure
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#9
3rd March 2016, 07:28 PM
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Mine used to run ok with the rear breathers completely in tatters so I'd not be too hopeful that that will help.
It is just barely possible to change them without removing the manifold or throttle body but might not take any less time. Certainly you will swear less and lose less skin if you remove the manifold! You say the ICV has been changed but are all the pipes/passage ways either side of it clear and able to pass air? What idle speed do you have in neutral? Should be 800 rpm IIRC. That's about what mine is, and it drops to about 500 rpm when in drive but shows no sign of wanting to stall. Nick
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