Crazy fuel consumption - what can it be?
Right, update...
I am slowly going through the suggestions from everyone by way of elimination until I get to the bottom of this. Have eliminated a leaking fuel tank as the car hasn't been driven for 2 weeks and fuel level is the same.
I went through the pain of replacing the new Denso IK22 spark plus with the standard NGKs, as well as checking the air box and MAFs for dirt or contamination from my new K&N filters. The airbox was squeaky clean, MAFs the same and there is no sign of oil residue from the filters anywhere.
What I did find though is that the new Denso plugs, which have done under 200 miles were already totally black on the tips and thread which doesn't look right. Could this suggest that the plugs were the issue, or a black plugs the sign of something else?
I will drive it this weekend to see if there's any improvement. If it still drinks fuel it has to be either a faulty MAF or a faulty fuel tank sensor.
Mart.
I am slowly going through the suggestions from everyone by way of elimination until I get to the bottom of this. Have eliminated a leaking fuel tank as the car hasn't been driven for 2 weeks and fuel level is the same.
I went through the pain of replacing the new Denso IK22 spark plus with the standard NGKs, as well as checking the air box and MAFs for dirt or contamination from my new K&N filters. The airbox was squeaky clean, MAFs the same and there is no sign of oil residue from the filters anywhere.
What I did find though is that the new Denso plugs, which have done under 200 miles were already totally black on the tips and thread which doesn't look right. Could this suggest that the plugs were the issue, or a black plugs the sign of something else?
I will drive it this weekend to see if there's any improvement. If it still drinks fuel it has to be either a faulty MAF or a faulty fuel tank sensor.
Mart.
C6 RS6 Plus with a few sensible mods...
Black plugs are not a good sign. Sign of rich running. You are going to need to put the car on the vagcom to see what's screwed up. Could be MAFs (My money is on these) or lambda sensors. These are the most likely culprits.
They shoudl look ilke this:
They shoudl look ilke this:
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
black plugs are a sign of overfuelling ( which you have established already by your MPG) it could be a leaky seal on an injector flooding the engine while running
2003 RS6 Avant
Avus Silver
KWv3 Coilovers
Hotchkiss ARBs
Wagner carbon fibre intercoolers
Milltek resonated cat back
20" C6 RS6 alloys
Kenwood multimedia centre
Unit 20 engine and gearbox remap
Avus Silver
KWv3 Coilovers
Hotchkiss ARBs
Wagner carbon fibre intercoolers
Milltek resonated cat back
20" C6 RS6 alloys
Kenwood multimedia centre
Unit 20 engine and gearbox remap
Cold start device? Could it be that your temperature sender is telling the ECU that the engine is cold? Is the temp OK on the dash?
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
Good point about temperature guage - does it show that the engine is running cold all the time? My brothers S6 had a duff coolant sensor and the car slowly became worse in terms of MPG and then difficult to start when cold. ECU was being told that engine was cold and was therefore running the thing rich as a result. £25 swap and all was right again.
Phil G
Phil G
Most generic OBD2 readers will give you access to the air flow readings...
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."
MAF sensors on VAG cars are a nightmare they rarely shown up as fault. You need to log the actual and expected values with a VCDS or similar it's the only way to be 100%Ceveman73 wrote:As part of the MRC health check the car was plugged into the VAGCOM for any fault codes and there were none. Wouldn't VAGCOM be able to detect a faulty MAF?
Mart.
VCDS is the new name for VAG-COM diags software - see http://www.ross-tech.com/ for more info.Ceveman73 wrote:Can you elaborate on what VCDS or similar are?
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300gnspitzer
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Right - since changing the plugs and carefully re-installing the airbox nice and snugly, fuel consumption seems to have improved dramatically! It seems strange that the plugs could makesuch a difference, but apart from a poorly fitted airbox, nothing else has been touched.
Just goes to show, it pays to use OEM parts!
Cheers for all your help.
Mart.
Just goes to show, it pays to use OEM parts!
Cheers for all your help.
Mart.
C6 RS6 Plus with a few sensible mods...