When to replace MAFs?
I see what you mean about the 364.08 max value. That is just weird. I don't know why it would be limited, but 364.08 / 0.8 = 455
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."
I'm just looking at some logs from a friend's S4 B5 and his lambda correction doesn't go to zero under WOT. Quite the opposite, it goes to full enrich... What could that mean?
On lift off, his lambda correction goes to zero.
On lift off, his lambda correction goes to zero.
- Attachments
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- LOG-01-001-002-115.xls
- S4 B5 logs
- (58 KiB) Downloaded 53 times
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."
I bit the bullet and have just had my MAFs replaced and the seals changed - I thought they were just o rings but the lower seal to the mafs is actually a mount so cost me about 25 quid each! It feels a bit swifter but will do some logs soon for a back to back comparison - old vs new!! I also had the vacuum hosing replaced while the air box was off.
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RS6-4dr911
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Semi-ditto - mine goes in Thursday for new MAF's, new N75 and top seals only. Bottom are unlikely to be bad, we'll check when it's apart and deal with it then. I'll run some logs before and after as well.paul_23 wrote:I bit the bullet and have just had my MAFs replaced and the seals changed - I thought they were just o rings but the lower seal to the mafs is actually a mount so cost me about 25 quid each! It feels a bit swifter but will do some logs soon for a back to back comparison - old vs new!! I also had the vacuum hosing replaced while the air box was off.
I had looked back at some Lambda readings and they were well over 10% in certain spots, the Ross-Tech write up mentions that is beyond "normal" range, so that along with high variation between them, a low total reading, 48k miles and performance issues, seemed like a reasonable next move.
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RS6-4dr911
- 1st Gear
- Posts: 55
- Joined: Sun Jan 25, 2009 12:34 am
- Location: Houston, TX, USA
I have done a few VAGCOM logs and noticed the first thing is that at idle the 2 new MAFs are pretty much the same (approx 3.5 each). Normal cruising they seem to fluctuate and dont always match - sometimes by quite a difference.
On full load (and I did some long pulls in 4th from 2000 to 5500 rpm) they both climb and are fairly well matched but are not identical - they are better than the old ones. I have not been logging blocks 1-2-3 so dont know lambda.
However, since the MAF change I have got fault codes:
2 Faults Found:
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
P1128 - 001 - Upper Limit Exceeded
17538 - Fuel Trim: Bank 2 (Mult): System too Lean
P1130 - 001 - Upper Limit Exceeded
These appear even after clearing them and only after gentle driving. Not sure what has caused these but they were not there before MAF swapped out. I do note that it is not silky smooth on full throttle around 2500rpm but smooths out after 3000rpm so it may be holding back. I checked the idle stabilisation correction factors (block 20-21) and the values go up to max 7 (at 5000rpm) which I have been told is ok but should not go above this.
Of interest, the MafS were replaced at the AUdi dealer in Dubai and I showed them my print out of MAF values to show them the problem. The german chief foreman came out to review and agreed but when he handed the car back he said they can't log them like I did as their software isn't able! I told him it is VAGCOM worth a few hundred dollars and he looked amazed and asked for me to keep him advised how they perform because he likes my car! I will try to get in touch with him to ask about these new fault codes.
Paul
On full load (and I did some long pulls in 4th from 2000 to 5500 rpm) they both climb and are fairly well matched but are not identical - they are better than the old ones. I have not been logging blocks 1-2-3 so dont know lambda.
However, since the MAF change I have got fault codes:
2 Faults Found:
17536 - Fuel Trim: Bank 1 (Mult): System too Lean
P1128 - 001 - Upper Limit Exceeded
17538 - Fuel Trim: Bank 2 (Mult): System too Lean
P1130 - 001 - Upper Limit Exceeded
These appear even after clearing them and only after gentle driving. Not sure what has caused these but they were not there before MAF swapped out. I do note that it is not silky smooth on full throttle around 2500rpm but smooths out after 3000rpm so it may be holding back. I checked the idle stabilisation correction factors (block 20-21) and the values go up to max 7 (at 5000rpm) which I have been told is ok but should not go above this.
Of interest, the MafS were replaced at the AUdi dealer in Dubai and I showed them my print out of MAF values to show them the problem. The german chief foreman came out to review and agreed but when he handed the car back he said they can't log them like I did as their software isn't able! I told him it is VAGCOM worth a few hundred dollars and he looked amazed and asked for me to keep him advised how they perform because he likes my car! I will try to get in touch with him to ask about these new fault codes.
Paul
Sounds like unmetered air getting in. You sure those seals are installed properly? That error is from when the lambda values are out of spec and the car can't enrich the mixture enough to compensate.
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."
Hold on. Could be that the ECU needs to adjust the trim to new values to take into account the new MAFs. Not sure how to go about that. Perhaps disconnect the battery for a while?
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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RS6-4dr911
- 1st Gear
- Posts: 55
- Joined: Sun Jan 25, 2009 12:34 am
- Location: Houston, TX, USA
Before and after logs
Replaced MAF's, top seals and N75 today. Before and after logs seem to indicate the variation between banks has narrowed considerably. They are also indicating higher readings by about 5% (used the average of all runs before and after, taking the MAF divided by RPM while under full boost).
Butt dyno says a little snappier off the line. Waiting for dry weather to see what the impact on 0-60 times is.
Butt dyno says a little snappier off the line. Waiting for dry weather to see what the impact on 0-60 times is.
Cool. WOuld be useful if you could post the 1, 2 & 3 groups for a direct comparison with previous value.
I've ordered 2 MAFs even though I'm sure mine are fine. For the sake of the experiment
I've ordered 2 MAFs even though I'm sure mine are fine. For the sake of the experiment
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."
Agreed! 
Clive
S2 ABY coupe, S4 B5 saloon, S4 B6 avant
RS4 B7 phantom black saloon, mint, fully loaded, low mileage - FOR SALE!- http://www.rs246.com/index.php?name=PNp ... ic&t=88981
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S2 ABY coupe, S4 B5 saloon, S4 B6 avant
RS4 B7 phantom black saloon, mint, fully loaded, low mileage - FOR SALE!- http://www.rs246.com/index.php?name=PNp ... ic&t=88981
S8 D2 facelift, RS6 C5 saloon, both gone but not forgotten
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