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Thread: MAF readings discrepancies

  1. #1
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    MAF readings discrepancies

    Hi all,

    I've been chasing my tail for a while with a very strange MAF discrepancy issue between bank1 and 2 on my car (Audi RS6 C5 2003), so I'm now looking for guidance from the bright minds.

    Symptoms are that - as seen on the advanced measuring values on my Hexnet- as long as the engine temp (coolant) stays below 80C, readings on both MAFs are perfectly aligned within a 5-7% margin, but above 80C, value of maf bank 1 starts to decrease little by little compared to bank 2. When the engine reaches a stable temperature (90-95C), the discrepancies between banks are as high as 70%, and like 40-50% when idle... Of course I get a fault code on the engine ECU (and that's the only one) saying I have implausible MAF discrepancy : '17416 - Mass Air Flow Sensor 1/2 : Implausible Signal - P1008 - 004 Intermittent'.
    To cut a long story short, I've already checked all hoses (including vaccum hoses) and seals, swapped the MAFs (same readings), checked the SAI valves/system, changed the EVAP solenoid (N80), along with the N112 and N249, without success. A quick air pressure leak test on the air inlets didn't show anything to worry about...

    Sooo after chasing a physical/mechanical problem (maybe it's still the case!), I start to wonder whether something could be wrong with the control /electrical system, like - off the top of my head - the engine ECU not receiving correctly the temperature sensor of one of the MAFs for gaz expansion compensation. Would that explain the strange and slow shift around 80C? Could a faulty ECU remap create such a phenomenon (my car is remapped but rewriting the stock map didn't change anything, except performance) ? Still scratching my head on this issue, so any help/suggestion is welcome!
    Best
    Last edited by Classik; 04-20-2019 at 07:46 AM.

  2. #2
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    CLASSIC, okay most mostly a TDI guy but As I see it. Cold engine might be tighter then as warms tolerances fade. That is making assumption each bank has its own MAF, could be wrong.

    Would be looking at compression check. As have no scan DON'T
    know mileage wear factor here?

    Would suspect one bank not as efficient as the other, just an opinion.

    Also post an auto scan as you will be requested to do so as were only as brite as the info we have?

    Good hunting

    LARIMORE

  3. #3
    Benevolent Dictator Uwe's Avatar
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    So even with the MAFs swapped, the problem (lower readings at higher temperatures) remain on Bank 1?

    Have you considered the the possibility of some wiring problem or connection that has a resistance change with temperature? Perhaps a dodgy ground connection on one side?

    -Uwe-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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  5. #4
    NostraJackAss Jack@European_Parts's Avatar
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    I start to wonder whether something could be wrong with the control /electrical system, like - off the top of my head - the engine ECU not receiving correctly the temperature sensor of one of the MAFs for gaz expansion compensation. Would that explain the strange and slow shift around 80C? Could a faulty ECU remap create such a phenomenon (my car is remapped but rewriting the stock map didn't change anything, except performance) ? Still scratching my head on this issue, so any help/suggestion is welcome!

    Who is the tuner?

    FOD!
    https://forums.ross-tech.com/showthr...uot-JPPSG-quot

    Remap most likely causing problem or not reporting the entire story in stack.

    European Parts Emporium/Performance / Immobilizer Solutions EPE
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    Above Magic! No Written record, AUTO-SCAN or Appointment = NO HELP!
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  7. #5
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    Thank you for replies and suggestions! I checked the wiring and admittedly with theses cars the MAF connectors are never in great shape due to the VERY small space behind the engine. So yes this may well be a reason. All main grounding points have been checked and cleaned no later than last Wednesday, so we should be covered.. except if the wiring doesn't follow of course.
    However I'm puzzled to hear an impedance dependancy to temp but you guys know better than me.

    Mapper is CTF Performance (in France-serious people), but as we speak I'm running the stock map (got an external device which allows to write map at will). Does that help?

  8. #6
    NostraJackAss Jack@European_Parts's Avatar
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    You mean switched or completely re flashed?

    Most of time if not complete reflash the nefarious tasks still exist in most tuners alleged but not actually a stock map.
    European Parts Emporium/Performance / Immobilizer Solutions EPE
    Certified Master Trained NY/BAR/BAD 7076062/ASE/SAE/NASTF Legal Factory Authorized/Licensed GeKo/FaZit # 403738
    Specializing in Custom Services IE: "welding-fabrication" / EPA-SMOG Update or Pass-Thru-Programming / Data Transfer / Immobilizers & OEM Quality Parts
    Above Magic! No Written record, AUTO-SCAN or Appointment = NO HELP!
    www.FixMyEuro.com <<<<<CLICK HERE! or vwemporium@aol.com ( JPPSG & Unverified members need not PM me & Please don't email or call facility for free tech support...use the forum )
    Getting you CONTROL again of your property - TAKE IT! In Conjunction with.........

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  10. #7
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    I meant completely reflashed, the whole process takes like 10 minutes.
    The map is supposed to be an oem map, but how could I know for sure..
    Is there a way to check if the MAFs readings have been changed / tricked in any way?
    Many thanks!

  11. #8
    NostraJackAss Jack@European_Parts's Avatar
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    Not VCDS related.

    Install known stock parts, perform repairs as per RTFB using VCDS blocks, codes reported and with aid of mechanical and electronic testing equipment such as load light and DVOM.
    European Parts Emporium/Performance / Immobilizer Solutions EPE
    Certified Master Trained NY/BAR/BAD 7076062/ASE/SAE/NASTF Legal Factory Authorized/Licensed GeKo/FaZit # 403738
    Specializing in Custom Services IE: "welding-fabrication" / EPA-SMOG Update or Pass-Thru-Programming / Data Transfer / Immobilizers & OEM Quality Parts
    Above Magic! No Written record, AUTO-SCAN or Appointment = NO HELP!
    www.FixMyEuro.com <<<<<CLICK HERE! or vwemporium@aol.com ( JPPSG & Unverified members need not PM me & Please don't email or call facility for free tech support...use the forum )
    Getting you CONTROL again of your property - TAKE IT! In Conjunction with.........

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  13. #9
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    Quote Originally Posted by Jack@European_Parts View Post
    Install known stock parts, perform repairs as per RTFB using VCDS blocks, codes reported and with aid of mechanical and electronic testing equipment such as load light and DVOM.
    I can only concur with the above, wise recommandations of course, particularly the electrical circuit check.

    Quote Originally Posted by Jack@European_Parts View Post
    Not VCDS related.
    Sorry but I don't fully understand. Mind expanding on that? Thank you!

  14. #10
    NostraJackAss Jack@European_Parts's Avatar
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    Sorry but I don't fully understand. Mind expanding on that? Thank you!
    No not really, pretty self explanatory.
    European Parts Emporium/Performance / Immobilizer Solutions EPE
    Certified Master Trained NY/BAR/BAD 7076062/ASE/SAE/NASTF Legal Factory Authorized/Licensed GeKo/FaZit # 403738
    Specializing in Custom Services IE: "welding-fabrication" / EPA-SMOG Update or Pass-Thru-Programming / Data Transfer / Immobilizers & OEM Quality Parts
    Above Magic! No Written record, AUTO-SCAN or Appointment = NO HELP!
    www.FixMyEuro.com <<<<<CLICK HERE! or vwemporium@aol.com ( JPPSG & Unverified members need not PM me & Please don't email or call facility for free tech support...use the forum )
    Getting you CONTROL again of your property - TAKE IT! In Conjunction with.........

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