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So, it started when i got CEL with code p0172: system too rich bank1. I took the car to the mazda dealer, they said you need to replace MAF sensor. I agreed and got the new sensor installed.

Now CEL is off but I still have low ltft readings specially at idle (-14%) which goes up to (-8%) when im on highway and to 0% when im driving above 80 mph. Im feeling like the numbers are getting lower every day coz when I first checked ltft after MAF replacement it shows minimum (-7%) then -11 and now -14. Im sure the code will come again in couple days or a week. The same happened before and I refunded the MAF when same code pops up again. I need help because the dealer is not willing to check low ltft unless there is a code.. and when they clear the code it will take time to reach -16 or -18 again. So they are doing bad diagnosis and clearing code without solving the problem.

Stft is low also. Ranging +3 to -10. The ltft numbers are not getting positive at all. I noticed that when the boost is positive the numbers improves or go to zero, and when vaccum it will go negative. Sometimes I smell gasoline around the car but not strong.

MAF reading is 3.5 g/s at idle and goes up to 200 maximum when wot at high speeds.

Also, I notice that the power is not as before. When accelerating I feel like small hesitation in rpm around 3 to 4 thousands and acceleration is not very robust. It feels like choked sometimes specially when its driven for long periods.

The car starts normally in the morning and warms up smoothly and have no rough idling.

I did some research but did not find something useful for turbocharged engines.

I just replaced turbo. I cleaned the oil control valve (sometimes called vvt) and I replaced sparkplugs. I have no modification at all. Everything is stock and OEM parts only.

Btw, I have fuel rail pressure 1660 psi and when I checked the workshop manual it says its within range of high pressure fuel pump (Fuel_pres pid shall be approx 11.5 Mpa.)

All air intake system is checked for leakage several times and no leak detected.

O2 sensor voltage is within range 0.1 to 0.8 and is responding to throttle changes. I think that o2 is working properly because its giving rich readings and I smell gasoline.

When I turn on the cold Air condition while idle, the ltft readings go to -11% and MAF reading go up to 5.5 g/s

My question: how to diagnose if leaking injector or bad cat or pinched return fuel line or blocked exhaust pipe?? I dont want to get this same code again because when it pops up, the car will drive slow and not responding to throttling. Also, I dont want to leave it like this and maybe get bigger problems in future.

Any help or ideas are welcomed.

Thanks.

Update: yep, it happened. Today I noted that numbers are getting lower and reaches -16 ltft and -10 stft.. sure I got CEL on as expected... so the MAF has nothing to do with this issue.

I captured the freeze frame and code log data:

Freeze frame report:

Vehicle VIN: JM7ER193XA020****

Vehicle Manufacturer: Unknown

Vehicle Calibration ID: L3CCEA000L

Freeze frame information:

Fuel Status = 0 byte

Engine Load = 26.275 %

Engine Coolant Temperature = 99 °C

Fuel Trim Bank 1 Short Term = -6.25 %

Fuel Trim Bank 1 Long Term = -16.406 %

Intake Manifold Pressure = 4.641 psi

Engine RPM = 694 rpm

Speed (OBD) = 0 km/h

Timing Advance = 11 °

Intake Air Temperature = 46 °C

Mass Air Flow Rate = 3.04 g/s

Throttle Position(Manifold) = 12.157 %

Run time since engine start = 3,107 s

Fuel Rail Pressure = 427.861 psi

EGR Commanded = 0 %

Distance travelled since codes cleared = 1,956 km

Barometric pressure (from vehicle) = 14.359 psi

Voltage (Control Module) = 13.196 V

Engine Load(Absolute) = 20 %

Commanded Equivalence Ratio(lambda) = 1

Relative Throttle Position = 3.529 %

Absolute Throttle Position B = 12.157 %

Accelerator PedalPosition D = 31.373 %

Accelerator PedalPosition E = 20.392 %

End of report.

Fault log report:

Vehicle VIN: JM7ER193XA020****

Vehicle Manufacturer: Unknown

Vehicle Calibration ID: Not present

Current Fault Log

P0172: System too Rich (Bank 1)

Pending Fault Log

ECU reports no pending faults

Historic Fault Log

ECU reports no historic faults Other discovered fault codes

(possibly pending, current or manufacturer specific)

ECU reports no other fault codes logged

End of report.

  • Is this a 2011? Can you add a road test datalog? We need info at idle and steady cruise. – Ben Jun 17 '17 at 13:02
  • 2010 cx7 2.3L gasoline with turbocharger. What readings you want to be logged?. – MAK Jun 17 '17 at 13:10
  • RPM, TPS, LTFT, STFT, ECT, IAT, AFRV, Both load PIDS, BARO, MAP, MAF, FRP and injector pulse width. Also add a wide open throttle log from 2nd to 3rd gear. If you can, change your pressure units to in HG (for air) or kPa (air or fuel) – Ben Jun 17 '17 at 13:18
  • @Ben is it possible to do all that log with torque pro? Anyway, at idle the ltft readings are fixed at -16. Steady cruise at low speeds will get ltft up to -7. Cruising at high speed without accelerating or lets say with low load will get ltft up to 0% – MAK Jun 17 '17 at 13:21
  • @Ben, ok RPM, TPS, LTFT, STFT, ECT, IAT, BARO, MAF, FRP. but what is Afrv? And how to get injector pulse width data and map readings? Also what do you mean from 2nd to 3rd gear? I will try to wot at 2nd and then shift to 3rd while wot. Thanks for reply – MAK Jun 17 '17 at 13:30
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I have the same problem, if you put compressed air can upside down on the throttle body sensor in the front it jumps fuel trims all around. When popping the hood the hot air comes out from the ac. then the throttle body sensor starts cooling off again taking the fuel trims down and further down. Try this!

  • Its the electronic throttle body that needs replaced, somehow the ac kicks on and the heat from ac cooling fan shoots on the black sensor part making it go super rich. Negative ltfts, if you let off throttle all the way it goes -11 to -16 if you turn ac on it can go to -18 or more then put cold air on the sensor part of throttle body and bam it corrects normal. The mazda can take up to 4 mins to correct, it wont be fast so wait before you deny this, the stft will correct then start pulling down ltft to 0 . – RedMustang1987 Jun 9 '18 at 0:59
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P0172: I strongly recommend you to check connector of MAF and MAP sensors. specially MAF sensor due to its location near Engine Air Filter, so every time you clean or replace that filter they disconnect then reconnect the MAF, usually technicians tend to pull it by wire (which can damage or loosen the connection).

Your description and readings seems normal and since this is an intermittent issue, I can tell you its due to loose connection.

Try to gently wiggle MAF wires inside connector while monitoring STFT readings, If you notice sudden change -- BINGO -- so you need to replace / repair that bad connector.

no need to change MAF if its working, specially that you already tried that !!!

Now, For the performance issues, check your VVT mechanisms and parts or filters, specially that little one inside the bolt...

good luck

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