If I am driving along at steady pace on motorway (ie neutral throttle and no boost), and I push the pedal to accelerate the engine pulls OK but then it hesitates and seems to pull back as the boost climbs. Always seems to happen between 2700 and 3100 rpm which corresponds to max boost. I have MTM remaps. If I floor it from standstill it is not a problem and pulls well - it is only when the boost comes in mid range.
VAGCOM shows faults that are 4 faults:
4 Faults Found:
17546 - Fuel Trim: Bank 2 (Add): System too Lean
P1138 - 001 - Upper Limit Exceeded - Intermittent
17537 - Fuel Trim: Bank 2 (Mult): System too Rich
P1129 - 002 - Lower Limit Exceeded - Intermittent
17535 - Fuel Trim: Bank 1 (Mult): System too Rich
P1127 - 002 - Lower Limit Exceeded - Intermittent
17544 - Fuel Trim: Bank 1 (Add): System too Lean
P1136 - 001 - Upper Limit Exceeded - Intermittent
MAFs are new (4 months ago) and all the upper and lower seals/seats were replaced after the MAFs because the same fault codes appeared. After they changed the seals the faults went away but it still never felt really smooth. It is as though the seals can withstand a certain amount of boost and then at a certain boost level they leak, drop the boost and cause the hesitation.
After the last big service (2 months ago) the hesitation was worse so I removed the air boxes and tried to reseat the MAFs in the o rings seals properly - they never seem to be a really good fit and there is no way to secure the air box tight down at the rear so it relies on self weight and the bolts/grommets at the front? Have you guys found this too?
So I have a few options:
1. Replace all the seals again and see if it cures it (this would cost about 100 quid for the seals and female lower sections) but do I have to do this every time the airboxes are removed
2. Try to secure the airbox at the rear so it fits tighter in the o-rings of the intake
3. Build up the MAFs surfaces with duct tape so they are larger - increasing the tight fit of the o-rings.
Any comments/ suggestions?
Cheers
Hesitation as boost increases - MAF O ring seals?
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posterboyj
- 4th Gear
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RE: Hesitation as boost increases - MAF O ring seals?
when I saw thread title I thought it might be the coilpacks failing.:..
use vagcom.to test the health of the lambda sensors and WOT log of block 002 for the max airflow and block 032 whilst idling
use vagcom.to test the health of the lambda sensors and WOT log of block 002 for the max airflow and block 032 whilst idling
Cornishmoocher wrote:Buying an RS6 and then worrying about the fuel consumption is a bit like buying a boat and worrying about getting it wet.
RE: Hesitation as boost increases - MAF O ring seals?
Sounds like the boost hose(s) or intercooler(s) are leaking. Will give you too lean at low revs (unmetered air entering system) and rich under acceleration (pressurised metered air escaping).
I am presuming that these are not old DTCs, that you have cleared them and they have come back.
I am presuming that these are not old DTCs, that you have cleared them and they have come back.
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."
RE: Hesitation as boost increases - MAF O ring seals?
Also what do what posterboyj says. If the air flow is normal through the MAfs, that would tend to give weight to my idea.
Log also 115 to see what the boost is doing;
Log also 115 to see what the boost is doing;
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."
RE: Hesitation as boost increases - MAF O ring seals?
Yes, the DTC were cleared and re-appeared.
The IC hoses and ICs were tightened/inspected and no sign of leaks (like oil residue) but it could still be an issue....
I will log some blocks and see what I get.
The IC hoses and ICs were tightened/inspected and no sign of leaks (like oil residue) but it could still be an issue....
I will log some blocks and see what I get.
RE: Hesitation as boost increases - MAF O ring seals?
Could be bad MAFs, but I don't think it the seal, not with the running too rich DTC. If you're taking the airbox off, check the 2 hoses going to the turbos from the MAFs. It sounds like it must be an air leak problem. It's the rich running DTC that makes me think its on the boost side of things.
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."
RE: Hesitation as boost increases - MAF O ring seals?
Also, if you can, try clearing the DTCs and driving really gently (ie off boost) to see what DTCs appear. Do the same driving it moderately hard (but not WOT) to see what DTCs appear.
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."
RE: Hesitation as boost increases - MAF O ring seals?
Yes, already done this. Gentle driving shows no hesitation and no DTC. It is only when I am cruising then accelerate (ie no boost, then boost climbs) that I get the faults.
Cheers
Cheers
RE: Hesitation as boost increases - MAF O ring seals?
Cleared DTCs and logged it for 1 hour during on/off fast driving. At the end got one DTC:
1 Fault Found:
17537 - Fuel Trim: Bank 2 (Mult): System too Rich
P1129 - 002 - Lower Limit Exceeded - Intermittent
I logged 001, 002 and 115 (boost).
Key things I noted:
On idle MAFS are fairly similar and are about 3-4.5
On part throttle or no throttle one MAF is about half the reading of the other.
On hard throttle and boost the MAFs equal out and are fairly closely matched.
The boost values are quite different (I assume the 3rd column is actual, 4th column is requested). If I squeezed the throttle and the requested boost raised to anything less than 1300, the actual would rarely change. If the requested went over 1300 then the actual would increase and try to match it but fluctuate.
When the hesitation occurs, the boost alters quickly in steps.
The above indicates to me that there is a leak on one bank (which bank refers to the 3rd maf reading in block 2 as this is the one with lower maf values. It also indicates that the N75 boost control solenoid might be faulty (it was replaced last year) as it is struggling to maintain the boost - but if there is a leak then the boost will be erratic.
Any other thoughts?
Is the N75 solenoid easy to replace DIY (i have removed the airboxes before so I assume it is under this).
1 Fault Found:
17537 - Fuel Trim: Bank 2 (Mult): System too Rich
P1129 - 002 - Lower Limit Exceeded - Intermittent
I logged 001, 002 and 115 (boost).
Key things I noted:
On idle MAFS are fairly similar and are about 3-4.5
On part throttle or no throttle one MAF is about half the reading of the other.
On hard throttle and boost the MAFs equal out and are fairly closely matched.
The boost values are quite different (I assume the 3rd column is actual, 4th column is requested). If I squeezed the throttle and the requested boost raised to anything less than 1300, the actual would rarely change. If the requested went over 1300 then the actual would increase and try to match it but fluctuate.
When the hesitation occurs, the boost alters quickly in steps.
The above indicates to me that there is a leak on one bank (which bank refers to the 3rd maf reading in block 2 as this is the one with lower maf values. It also indicates that the N75 boost control solenoid might be faulty (it was replaced last year) as it is struggling to maintain the boost - but if there is a leak then the boost will be erratic.
Any other thoughts?
Is the N75 solenoid easy to replace DIY (i have removed the airboxes before so I assume it is under this).
RE: Hesitation as boost increases - MAF O ring seals?
The MAF's should be within approx 10% of each other.....
3-4.5 is fine on Idle, try reseating the airbox.
edit.. saying that it would be lumpy if the box was not seated. Probably a bigger leak..
Drop the under tray and check your IC hoses.
3-4.5 is fine on Idle, try reseating the airbox.
edit.. saying that it would be lumpy if the box was not seated. Probably a bigger leak..
Drop the under tray and check your IC hoses.
Steve
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RS6 gone, R32 gone, M3 gone, Porsche Cayenne Turbo gone, Boring A6 saloon gone, Boring A6 Avant going in 5 weeks
. Maybe RS5 or S5 Hatchback to come...
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RS6 gone, R32 gone, M3 gone, Porsche Cayenne Turbo gone, Boring A6 saloon gone, Boring A6 Avant going in 5 weeks
. Maybe RS5 or S5 Hatchback to come...RE: Hesitation as boost increases - MAF O ring seals?
I'll be interested to know what the diagnosis is too. I think mine is doing exactly the same - almost like it kicks down a gear (which it doesn't) in fourth or fifth when you accelerate about 80% full. There's a stutter of confusion beforehand.
Audi are servicing her next week but it would be good to go armed with an accurate suspicion.
Audi are servicing her next week but it would be good to go armed with an accurate suspicion.
C5 RS6 Avant. Muggle Blue, Black leather, PSS9s, Hotchkiss ARBs, Grizz's BIG brake kit, Phaeton cooling ducts.
RE: Hesitation as boost increases - MAF O ring seals?
Swap the MAFs to eliminate them as a cause.
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."
RE: Hesitation as boost increases - MAF O ring seals?
I changed my MAFs out about 5 months ago. Slightly sharper feel and better VAGCOM readings but it was not a massive difference - my old ones probably were ok just a bit tired....
RE: Hesitation as boost increases - MAF O ring seals?
I have experienced similar hesitation in mine when you accelerate in normal drive mode from around 2000-3000 rpm to full throttle.
There's a stuttering in the power delivery.
I asked Grizz about it before, and he said it was the car protecting itself from the torque, because the car is effectively in too low a gear.
If you put it into sport mode so that the rev's are higher it doesn't happen.
There's a stuttering in the power delivery.
I asked Grizz about it before, and he said it was the car protecting itself from the torque, because the car is effectively in too low a gear.
If you put it into sport mode so that the rev's are higher it doesn't happen.
RE: Hesitation as boost increases - MAF O ring seals?
I meant swap MAF 1 with MAF 2.
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."
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