Bank 1 Running Lean

Arsalan Owner/Technician District of Columbia Posted   Latest   Edited  
Delayed
Driveability
2007 Infiniti G35 3.5L (VQ35DE) 5-spd (RE5R05A)
Bank 1 Running Lean

Hello

I have my own vehicle here in the shop today. I have actually purchased this vehicle from a customer of mine because of the check engine being on & vehicle leaking coolant from water pump.

I replaced water pump due to coolant leak and at the same time decided to do do timing chain, tensioner, guides and sprockets including thermostat with all OEM parts. 

Check engine light was on due to catalytic converter so I decided to do both catalytic converters & all 4 oxygen sensors (OEM Parts). I also decided to change MAF sensor, spark plugs & ignition coils (Hitachi).

I changed the parts because car was in a little bad shapes and not because I was just throwing all these parts on it to repair the Lean condition. Car drives very smooth and no shaking or misfiring or exhaust fuses at all.

My main concern is what can be causing a Bank 1 to run lean because my fuel trims at idle are about +22 and at highway it stays positive around +35 and bank 2 stays withing less than 10 at all time.

WHAT CAN CAUSE ONLY BANK 1 TO RUN LEAN?

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Larry Owner/Technician
California
Larry
 

Regrettably, being off a tooth on your chain on that side will give you that, not sure on how the tensioner sets up, but if its on that side, it could be your tensioner bad out of box? leaking intake manifold on that side, bad injector, could all as well? Im curious if it had lean codes before?

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Arsalan Owner/Technician
District of Columbia
Arsalan
 

No codes were there before only codes I found were P0420 & P0430,

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Jared Diagnostician
Maryland
Jared
 

Doesnt this have 2 MAFs? Can you try a flip flop and see of trims follow? One side intake boot torn? Just some thoughts.

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Arsalan Owner/Technician
District of Columbia
Arsalan
 

This have a single MAF and boot have been replaced already also since it was cracked a little.

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Glenn Owner/Technician
Texas
Glenn
 

If you have a propane bottle with a small tube attached, feed a little propane at the intake mounting surface for the problem bank. While doing that monitor the fuel trim. Allow some lag time for the O2 to read this. If the trims move toward normal, the intake had a leak on that side. Also inspect all vacuum hoses and connections carefully. As another member posted. Timing can be off by one…

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Arsalan Owner/Technician
District of Columbia
Arsalan
 

I have confirmed CMP & CKP Correlation and compared it to a known good and its exactly same.

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Elias Owner/Technician
California
Elias
 

My experience when a bank is off, the opposite will run on the rich SIDE​.​NOT always true but none the less…I would try and eliminate what you have done so far…maybe a sensor is reporting incorrectly. You could always swap from bank to bank as I think they may be the same part number…fuel injector could cause same issue as well…intake leak and then possible exhaust leak that may not…

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Paul Mechanic
Illinois
Paul
 

I would also thick you would set a cam/crank correlation code if that was case, so valve timing is probably not a issue. You changed O2S, so it's it possible you may have a bad one? Did O2 monitor run? As others have suggested, propane around intake and watch for fuel trim correction.

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Jordan Owner/Technician
Washington
Jordan
 

I've had so/so luck with this technique. What's your opinion on using ether instead?

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Paul Mechanic
Illinois
Paul
 

I bit too volitale in my opinion and coming out of spray can, tough to regulate and more dangerous overall. Not a huge fan of smoke due to the pressure being applied can actually help seal potential leaks that are only present with vacuum pulling a on them. Arsalan should verify all injectors are same calibration and flow if vacuum leaks are not present and valve timing is okay. He can also try…

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Paul Mechanic
Illinois
Paul
 

To be clear, my bottle of propane has a valve and flow gauge and hose that I can control output. I have even driven vehicles into shop with bad fuel pumps with my thumb on button and dialing in the correct amount to support combustion. I have used carb/brake clean in short bursts as a quick check to see if there is any affects on trim and then pinpoint with propane.

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Tyler Technician
Kansas
Tyler
 

I know you don't hear an exhaust leak, but a leak between the upstream and downstream sensors on bank one would create a downstream fuel control issue. You can clear the Self Learn values and see if the trims come back into line. If they do, pressurize the exhaust and use soapy water to look for leaks.

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Larry Owner/Technician
California
Larry
   

Im seconding what tyler said about adaptation, a lot has changed and maybe it has not adapted/reset yet? I dont know this car at all, how is the pcv set up? does it route back in to a central spot in the intake? or more on bank1? if so that might be an issue. it also appears to have a fuel damper on each rail and one in the fuel line, not sure what the effect of a bad damper would be on one…

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Stuart Mobile Technician
Illinois
Stuart
 

Is it the bank with the PCV valve in the valve cover?I had a vehicle recently with a similar issue and found it with going around the bank with a propane enrichment nozzle​.​Also found a leaking injector o-ring the same way.

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Stephen Technician
Tennessee
Stephen
 

I have seen an instance where an out of time bank was running normal FTs and the in-time bank FTs were skewed. Causing an initial focus on the wrong bank. A relative compression or in-cylinder of both banks may be the faster way to verify mechanical integrity. The cam/crank was good on that car but a gear had slipped.

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Cmore Mechanic
Connecticut
Cmore
 

If it wasn't there before the repairs and you say timing chain is ok I would look at the o2 sensors. Also no way a vacuum leak would cause +35 at cruise.

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Timothy Owner/Technician
Wisconsin
Timothy
 

There's no way that a vacuum leak is going to cause the fuel trims to be at +35 at cruising speed, with that much throttle opening. This is not a vacuum leak. Compare the CKP and CMP for BOTH banks, if you've not already done so. The are not a ton of possibilities here, since both the cats are OEM, I'd doubt that it's a breathing issue from the catalysts. Check the rear O2 sensors and see if…

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Jordan Owner/Technician
Washington
Jordan
   

Check for vacuum leaks. Not uncommon for one bank to run lean if the vacuum leak is on that side. Suggest fogging the engine with smoked mineral oil. Edit: Do the '07 VQ35DEs have intake manifold runners? This can also cause a lean bank code.

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Tommy Owner/Technician
North Carolina
Tommy
 

Arsalan, Is it possible to mix up the o2 sensor connectors?

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Arsalan Owner/Technician
District of Columbia
Arsalan
 

NO NOT AT ALL

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Arsalan Owner/Technician
District of Columbia
Arsalan Delay
 

Hello. I got hit by a car and my leg is injured so I will continue with this when I get better. I REALLY APPRECIATE ALL THE HELP.

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Stuart Mobile Technician
Illinois
Stuart
 

Hoping for a speedy recovery.

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Tommy Owner/Technician
North Carolina
Tommy
 

Arsalan, Sorry to hear that. Best wishes for your recovery.

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