Mazda CX-7 lean condition under load only

Roberto Owner/Technician California Posted   Latest   Edited  
Unsolved
Driveability
2008 Mazda CX-7 Sport 2.3L (MZR) 6-spd
P2177 — System Too Lean Off Idle Bank 1
This Vehicle Has A Problem With The Fuel Trims
Code Is Related To A Lean Condition
Under Load Only
Lack of Power

This truck has a lean condition under load, vehicle runs fine on idle, but under load is has lack of power and the fuel trims go well 25% positive, we tested the air fuel ratio sensor and at idle is responding to either a rich condition or lean condition, when we apply propane on the intake we can see the rear O2 sensor goes rich and the front air fuel ratio changes its reading too right away, and when we apply a vacuum leak the rear sensor moves to lean condition and the front also reacts to the opposite direction, the volumetric efficiency is at 153% under load that is 180 g/s at 5100 RPM, so Am assuming the efficiency is correct due to that this engine is turbocharged, the fuel pressure is about 65 PSI on the low side and the specs are about 65 to 73 PSI, I haven,t drive the truck with the fuel gauge connected to the low side, but with the car in the bay, all the time we raise the RPM we can tell it goes to lean side on higher RPM, the high pressure fuel pump PID is normal, as far as we can tell, the actual pressure is always almost the same as the desire pressure, the only question I'll have about the high pressure pump is that the maximum pressure under load only reaches to 1500 PSI but the desire is as I mentioned the same or very close, I was looking on service information and found out that there is a bulletin … that implies reprogramming the computer for this condition but according with the VIN number it doesn't apply to this vehicle for less than a month on production date, also there is another bulletin (01-009/13) regarding the air fuel ratio sensor that gets brake fluid and starts sending the wrong signal to computer, but we followed the procedure to test the O2 sensor with the scope and signal is good as far as we can see, also, we did the KAM reset with the same result.

So, the question for you guys is, what else can be causing my lean condition? did I cover all the basics? it looks like we did, but don't know exactly what to recommend to customer, I was thinking to reprogram the computer as part of the diagnosis and see what is the result, but I have also the question that when reprogramming a Mazda CX-7 do I have to reprogram the keys too, since we have only one key. 

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Caleb Technician
Indiana
Caleb Default
 

Not gonna get very scientific here but I'll throw out a few tests. Definitley worth checking out the PCM update. Needs to be at the latest cal regardless​.​Injector issues. Could use secondary ignition to pinpoint a possible injector issue. Possibly full of E85. Possibly loose or stretched timing chain. Plugged CAT.

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Justin Mobile Technician
Utah
Justin Default
 

Too much alcohol will cause trim issues at all load conditions.

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Caleb Technician
Indiana
Caleb Default
 

Agree Justin. However I have also had several newer Chryslers that were E85 cars that the trims were perfect with no codes and they would not restart after a 15 minute hot soak. Removing the E85 and putting in regular 87 fixed them. There may have been a PCM update for this but the customers didnt want to look into it.

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Albin Diagnostician
Washington
Albin Default
 

Here is a case where doing a FRTD while gathering fuel trim and engine load data would be a great resource.

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Randy Diagnostician
California
Randy Default
 

Currentr ramp fuel pump

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Francisco Diagnostician
Virginia
Francisco Default
 

Have you check for leaks on the duct? Pressure side after the turbo?

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John Technician
California
John Default
 

That would make a rich condition.

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Geoff Diagnostician
Hawaii
Geoff Default
 

My experience with TSB is that if they are remotely close to what you are seeing / dealing-with, follow the bulletin. A few months either way is within the margin for error for the OEM's recommendations, IMO.

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Caleb Technician
Indiana
Caleb Default
 

And yes it slipped me in my first response. After seeing Franciscos reply and rereading you post. Yes definitely check for a boost or Charge Air System leak.

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Jim Mobile Technician
Pennsylvania
Jim Default
 

I REALLY think that you are jumping over the basics here, Fuel pressure and fuel volume are two entirely different things. You can absolutely have the correct pressure without the correct volume. Take the vehicle out for a test drive or run it on a dyno with that propane connected to the intake, when you get into a demand mode give it some propane. I think you will find your answer right there…

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Samuel Technician
New Jersey
Samuel Default
 

Excellent point Jim!!!! volume vs pressure, so easily forgotten when we get going down that rabbit hole!!!

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Francisco Diagnostician
Virginia
Francisco Default
 

Hi Jim, Question: this is a GDI engine so if the fuel rail sensor shows an actual and desire pressure matching all the time, would you still think that Volume can be off?

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Jim Mobile Technician
Pennsylvania
Jim Default
 

YES, Volume is Volume makes NO difference what type of fuel delivery it is. I just had a late model BMW that was back three times for a COP coil replacement and the actual ROOT cause was the end of the fuel rail was restricted with dirt and sediment causing a fuel restriction, in turn driving the Firing KV too high in order to combust the lean air / fuel mixture. This why I said "G" (General)…

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Chris Technical Support Specialist
New York
Chris Default
 

If the volume was insufficient, there would be a pressure loss assuming there is no restrictor after the pressure sensor before the injector.

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Eric Owner/Technician
Wisconsin
Eric Default
 

Sure, I agree. But . . . what if the injectors are where the restriction is? Then the cylinder is the only place that would see the reduced volume and pressure. The engine would show lean. How would you verify that on a GDI equipped engine?

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Chris Technical Support Specialist
New York
Chris Default
   

With the pressure sensor on the opposite end of the fuel rail than the inlet, this vehicle show a pressure drop to have a volume issue.

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Chris Technical Support Specialist
New York
Chris Default
 

Reprogramming will not require additional keys. New module installation is another story. Also just a heads up, If you are programming the module in house, make sure the software will not have conflicts prior to installing. Mazda MMP (j2534 for up to 2017 MY) will not work if installed on the same machine as IDS, MDS, FJDS, FDRS,or Mazda MDSFA. The cores of these softwares are similar and they…

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Randy Analyst
Colorado
Randy Default
 

These are high failure vehicles here in Colorado for either NOx or CO. I have a lot of data on the high CO vehicles and just a little bit of data on Nox fails. If you search the archives, I posted one that failed CO. DTCs are almost never present. First, reprogramming to the latest software won't fix these. Software version has no bearing on the fuel control issues. Second, there have been 9…

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