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Thread: Help diagnosing my lean AFRs

  1. Default Help diagnosing my lean AFRs

    Hi guys, I have a 2006 Mazda 6 MPS with a few basic mods.


    I am asking for help in diagnosing an issue that I am currently having, as many of you OZMPS forum members have a lot more experience with this platform than myself. Please excuse me if something I write or try to explain doesn't make sense, this is one of my first posts and I am relatively new to the wonderful world of car modifications.

    I am experiencing a lean issue when going WOT (see 3rd WOT to 5000rpm datalog). This issue occurred in my current map and also in a Cobb OTS tune stage 2(95 DP, SRI, TIP) that I trialed to see if the issue was due to a tune for a slightly different MAF housing. The Lean AFRs occur in all gears. The Measured AFR is varying quite a bit from the commanded AFR, (around 12.3-12.7 measured vs 11.3-11.7 commanded)
    I was running the S-OTS tune for 5000km plus without any issues, except for a bit of a boost spike which I guess is normal for an OTS tune.

    The issue first came about when I recently installed my CS Air box (ecu was reset due to having to remove the battery), as soon as this was installed the AFRs became lean.
    I have also noticed the AFR became rich after letting off the throttle or during shifts. (see datalog 1)

    3rd WOT to 5000rpm.csv
    Cruising.csv
    datalog1.csv


    Mods:
    -Cobb AP runningS-OTS stage 1 95 tune
    -CS SRI,TIP and Airbox
    -Custom 3 Inch dump pipe with 100 cell hi flow cat
    -Autotech hpfp
    -ITV22 Sparkplugs
    -JBR 80a Rear and Transmission mounts
    -JBR short shift plate
    -VVT and timing chain replaced as a preventative measure


    Troubleshooting/Fixesalready tried:
    -MAF sensor cleaned using "CRC mass flow sensor cleaner"

    -MAF sensor o-ring replaced. Ensuring MAF sensor is correctly in place when reinstalling.

    -Very carefully reinstalled the intake system. Thoroughly checked all clamps,ensuring they were on correctly, and all hoses leading to waste gate,boost solenoid, crank case and BPV (can't think of any others off the top of my head). Also checked for any cracks or excessive wear marks in any hoses/pipes. Spent a total of 4 hours going over everything.

    -Tried running the car without the Air box to see if the issue went away, but was unsuccessful.


    Otherpoints of interest:
    -I use Nulon 10w-40 HTFF oil and change it regularly.

    -I only use BP 98 fuel, or United P100.

    -I am currently experiencing a small amount of smoke from the exhaust after idling for a while, or while in slow moving traffic. The lean AFR were occurring well after the smoke started appearing. I realise the cause of the smoke is my stock turbo has oil leaking past its seals. (plan on upgrading to a bigger turbo soon)


    -The dump pipe I had fitted was from Best Mufflers in Sydney, the bloke does amazing work. I had this fitted approximately 5000km ago and have never had any CEL or issues with it. He showed me a lil extra he had fitted to the 2nd O2 sensor, which he explained as altering the signal for the emissions side of things. He said it shouldn’t alter any AFRs or affect the actual running of the vehicle ( I presume these things would be controlled by the primary O2 sensor)


    -The MAF housing has no air straightener

    -EGR plug is disconnected following RAYDs guide

    -Have not had any CEL, except from the EGR plug.


    Summary:
    So basically everything was working perfectly (or near enough to it) for awhile,then when I fitted the air box things went a bit not so perfect. This could merely be a coincidence.
    I am starting to think whether my BPV might be leaking and in need of an upgrade, or maybe if my MAF sensor or primary O2 sensor has messed up. If it was the latter however I assume that my MAF and AFR readings would be fluctuating greatly, and the car would run like poo, or plain not even start.

    So I am asking for the help of those of you with more experience and a better understanding of these cars, to help resolve my little issue.

    Thank you for taking the time to read my thread, any feedback/help offered is greatly appreciated.

  2. #2
    Join Date
    Apr 2010
    Location
    Canberra
    Posts
    9,459

    Default

    By s-ots is that the ones on Stratified which are for the power path intakes? Or the one where you fill out a form?

  3. Default

    Should have been more specific sorry. Its for the jbr power path intakes, I have read these have relatively similar intake diameters with the CS intakes.
    I had run this tune for some time without any issues. To rule this tune out as the culprit I ran a cobb stage 2 specifically designed for the CS intake, but unfortunately the lean issue remained.

    My guess is that the issue is mechanical/sensor related rather than a tune issue.

    Is it a possibility that while going over all the hose clamps I may have over tightened them? Nothing to crazy I can tighten a bit further still but felt they were already really tight.

    I also forgot to mention I use a CS dry flow filter not an oiled one.

  4. #4
    Join Date
    Jun 2009
    Location
    Newcastle
    Posts
    1,413

    Default

    I assume the fuel trims are in the + and above threshold limits?

    apart from obvious air inlet installing errors is the maf in the correct direction?

  5. Default

    Thanks for the replies and help so far.

    Yep fuel trims are generally in positives ranging from -2% at idle to +8% on acceleration, nothing to drastic which confuses me as to why AFRS would be out so much. I had let the trims settle for about 200km if that makes any difference.

    Maf housing is in correct orientation in regards to airflow, also have the MAF sensor positioned in the top off the housing. I have heard having it at an odd angle may trigger errors. Basically if you are looking through the housing, my sensor would be at the 12 oclock section of a clock, if that makes any sense?

  6. #6
    Join Date
    Jun 2009
    Location
    Newcastle
    Posts
    1,413

    Default

    Maybe try do a maf cal log following the procedure in one of the VIP threads, that should help.

  7. Default

    Thanks Mitch will give it a shot, have been meaning to donate and become VIP for some time, just never got around to it.

  8. #8

    Default

    Also, to rule out the very simple, have you cleaned the MAF?


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  9. Default

    Yep have cleaned with CRC Mass air sensor cleaner. Let it completely dry and also replaced the o ring. Have repeated this process several times to ensure I hadnt missed anything.

  10. #10

    Default

    With your mods, why are you not running a stage 2 map?

    Sent from my HTC One X

  11. Default

    Good question, I had tried running a stage 2 98 and also a 95 but found it to be spiking to 20+psi. There was no boost creep but the spiking was crazy, at some points it would hit above what the stock MAP sensor could read and out of safety opted for a lower stage, chose 95 over 98 for more knock protection. I really like the feel of the S-ots base tunes compared to the cobb ones much smoother yet more power.
    As mentioned in OP I had also tried running a cobb stage 2 + 95 tune suited to my mods, didnt get any spiking but same lean condition occured.

    I will give a MAF cal a shot as Mitch suggested and see if this fixes anything.

    Cheers for the posts, advice and help so far guys, keep em coming .

  12. Default

    Hi guys just a little update, was heading out to my logging road anddecided to flick through some monitors on the AP. Nek Minnit I notice the STFT going berserk, would be jumping from as good as -0.94 to as extreme as -25.00%or +20%. Sometimes it would be constantly changing (by a large amount) multiple times a second, while other times it might stay at -20% for a little while. I decided to abandon doing the MAF calibration logs especially WOT logs until I figure out what going wrong. These values were during closed loop/partial throttle conditions, with the throttle being held steady or gradually adjusting as needed (aka normal driving conditions). Also I noticed that sometimes it would stay in the high negatives (-20%) for awhile, then randomly change to high positives (+15%) for a while.
    I captured as much as I could through logs. I should also point outall logs were performed in a single trip, totaling ~15km/25mins on my commute to work.

    Datalog14 in particular shows varying negative and positive values in a short time, yet throttle/ mass air flow/rpm don't change too much.

    I think its important that I make mention that AFRs and STFT weren't like this previously, the tune was running nice,strong and smooth. The issue only presented itself recently.

    I have decided to make a list of the possible causes and would like your experience and knowledge to help add likely causes, eliminate unlikely causes and ultimately pinpoint the problem.


    Possible causes:
    -Faulty MAF sensor
    -No air straightener before MAF sensor
    -Faulty primary 02 sensor (could it possibly be dirty due to oil in exhaust gases, resulting from the turbo oil seal issue?)
    -Intank fuel pump could on its way out.
    -Possible faulty HPFP
    -Bad batch of fuel, filled up at Yagoona United with P100, recently after this fill up the symptoms and issues started appearing.
    -Stock BPV leaking/sticking
    -Purge solenoid valve

    When I get a chance I will try running the car with the stock air intake system to rule out a fault with my CS intake (I am extremely busy at work at the moment and haven’t had a chance to do so). Will also try and use up this tank of petrol and fill up from a BP servo with 98.

    Unfortunately I cant rush off and spend any money fixing/replacing parts it till I next get paid, as someone from overseas has very kindly emptied my bank account, heh I guess when it rains it pours

    I appreciate any opinions and help offered, and thank you so far for the help guys.
    Attached Files Attached Files

  13. #13

    Default Help diagnosing my lean AFRs

    STFT jump around all the time (although yours do seem a bit extreme). This shouldn't prevent you from doing a MAF cal though: you don't need to go WOT at all. Logging Maf G, Maf Volt, and LTFT. Watch the G reading, get into 2nd gear, slow down to a crawl so you are seeing 3-4g, then accelerate slowly and smoothly (you are trying to stay in closed loop and hit as many of the maf g readings as you can) to 100+ gs (should take you somewhere between 80-90km/h). Do that a few times then make the adjustments in ATR. Rinse and repeat. If you get your LTFT under control this way, then you can start looking into what's up with STFT.

    Before doing any of this though, Id do a proper boost leak test if you haven't before. If you can, disconnect and plug the BPV recirc hose (this will identify if your BPV is leaking) and the CCBH (avoid pressurising the CC), remove the MAF housing and pressurise the intake to 10-15 psi with an air pump. If that holds fine without any leaks then go ahead with your MAF cal log. If not, go leak hunting.


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    Last edited by Lachlan; 13-06-2014 at 08:07 AM.
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  14. #14
    Join Date
    Aug 2011
    Location
    Sydney North
    Posts
    441

    Default

    I say boost leak test too before you start anything else. I had pretty much exact same issues when I first started modding. Was all boost leaks.

  15. Default

    Thanks for that info Lachlan.

    The main reason for WOT maf cal was to also fix the lean AFRs at WOT. I would be doing a regular closed loop MAF cal as well of course.

    I abandoned the MAF cal because I wanted to make sure I didn't zoom zoom boom. Also to ensure I didn't tune around a fault. Will get stuck into the leak testing, and physical diagnosing today or tomorrow all being well.

    My STFT were never this crazy in the past is all, usually stayed within +-6%, except at WOT of course.

    Thank you again for taking the time to go into that great detailed response.

  16. Default

    Thanks for that reply Rob.
    Hopefully it is a simple fix like yours, then I can get stuck back into continuing to modify and improve my baby.

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