2006 Nissan Sentra 1.8l

Joe Technician Hamden, Connecticut Posted   Latest  
Question
Driveability
2006 Nissan Sentra 1.8L (QG18DE) 4-spd (RE4F03B)
P2A00 - O2 Sensor Circuit Range/Performance Bank 1 Sensor 1
P0171 - System Too Lean Bank 1

Got this vehicle in from another shop with code p2a00. They replaced a/f sensor twice over a few months. Verified code and scanned data stream. Found fuel trim at 136%. Cleared code and reset fuel adapt. Test drive vehicle and now getting p0171. P2a00 has not returned. Fuel trim returned to 136 at idle and cruising speed. Smoked intake found no trace of leak anywhere. Maf readings look good at 2.1 at idle and 8.2 at 2500 rpm. Found no exhaust leaks. Fuel pressure at idle is 57psi. A/f sensor is reading around 1.6v at idle. Also noticed during test drive under wot has a lack of power and trouble accelerating. Also tested back pressure which was only 2 psi at 2500rpm. Thinking possible injector/ fueling issue. Any common problems on these I could look for before diving into injector flow and fuel volume testing? Thanks in advance. 

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Justin Mobile Technician
Herriman, Utah
Justin Default
 

Check alcohol content.

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Martin Diagnostician
Burleson, Texas
Martin Default
 

Does the rear o2 sensor respond if it is driven lean and rich?

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Victor Owner/Technician
Doral, Florida
Victor Default
 

Maybe wrong sensor in right place or vice versa.

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Jason Technician
Hawthorne, New Jersey
Jason Default
 

First question is what's the freeze frame when the fault occurred. Temp, load, rpm?

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Kevin Diagnostician
Northland, New Zealand
Kevin Default
 

Cat blockage, cracked head or both. Worth keeping in mind.

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Bill Owner/Technician
Jackson, Michigan
Bill Default
 

Make sure the exhaust flex pipe is solid (use air pressure and soap or smoke to test for leakage) Rear O2 sensor performance?? Make sure you can force it rich/ lean and response is normal

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Diogo Owner/Technician
Fortaleza, Brazil
Diogo Default
 

Injetores com aplicação errada. Talvez uma falha na alimentação positiva dos injetores. Mas muito estranho os DTC's com um TRIM 136. Considero normal 10 - 128 + 10.

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Pam Owner/Technician
Tampa, Florida
Pam Default
 

Did you do all the preliminaries (i.e, electrical check, TSBs, etc.)? Electrical is the main-stay. Make sure you have consistent power/ground values Did you check fuel volume along with pressure check? (You can have great pressure and lousy volume.) Did you check vacuum with a gauge? (Hint: Gauge should drop a few inches of merc when ign is turned off, if an injector is…

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Michael Mobile Technician
Clinton, Utah
Michael Default
 

Common for these to have an stuck PCV at times. There is also a TSB for PCM update on many of these models. 136% is high to be fixed by update.

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Justin Mobile Technician
Herriman, Utah
Justin Default
 

What can cause fuel trim corrections equally across all loads? It isn’t a vacuum leak or MAF sensor.

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Michael Mobile Technician
Clinton, Utah
Michael Default
 

Hi Justin, I like your E85 theory. As we don't know all about the PCM strategy, there may be something that makes the ECU angry and it decides to put in it's own numbers. An open or sticky PCV may give an erratic signal and the ECU decides to go crazy. Just throwing ideas out there.

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Justin Technician
Concord, California
Justin Default
 

I’ve had a few of these with coolant entering cylinders check for hydrocarbons in cooling system using a tailpipe analyzer if any found like more than 20 ppm start there , coolant on a/f and o2 sensors will give false readings and wreak havoc

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Eric Instructor
San Luis Obispo, California
Eric Default
 

Lack of power during WOT takes the O2 sensor out of the equation. I've seen MAF problems that still have reasonable g/s readings.

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Richard Technician
Stony Brook, New York
Richard Default
 

HI Joe, take a good look at the intake boot. They develop splits that wont show up during smoke testing, because they are pushed back together. Last week I had a Sentra with that P2a00 code and the boot was split. I removed it from the vehicle and flexed it to confirm. Another way to check it would be to power brake it while someone looks at the boot. While its in the extended position from…

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Joe Technician
Hamden, Connecticut
Joe Update
 

Thanks for all the responses. A quick update the rear o2 is responding to adding or subtracting fuel but remains at .200v at idle. I hooked fuel gauge up again I either missed or didn’t notice earlier was fuel pressure drops to 0psi within 2 min of turning key off.

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Eric Instructor
San Luis Obispo, California
Eric Default
 

If you are thinking that your loss of pressure is from an injector, a leaking injector would not account for positive fuel trim. In fact you would see negative fuel trim. A leaking injector would also have less effect at high speed/WOT. I don't think your fuel pressure drop is meaningful in the context of your problem, as long as its normal during the incident. I'm still thinking MAF.

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

You need to tape the gauge to the windshield and drive WOT for 15 seconds. If it holds above minimum then the injectors are the issue.

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Justin Mobile Technician
Herriman, Utah
Justin Default
 

Geoff, can you elaborate on this procedure? WOT for 15 seconds? I’m fairly sure there isn’t a road in my town I could do that without breaking laws or running into traffic. What are you referring to when you say “hold above minimum”?

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

I forget not everybody lives on the side of hill. I guess I should have written WOT from a stop through the first shift, but if that car is as lean as we think, that might take 15 seconds. Fuel pressure should hold above minimum during the run. Checking fuel pressure in the bay, and then putting the gauge away (and doing something else) is leaving out an important part of the test, given that we…

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Justin Mobile Technician
Herriman, Utah
Justin Default
   

Got it. VE test drive.

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

and I think Albin calls it a FRTD (flat rate test drive). Over here we call it "flooring it up the hill". I started riding my bicycle up the hill as a change-up to my cardio routine a couple months ago. Still don't make it out of FIRST gear in spots (it's a 24 speed mountain bike).

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Frank Educator
Halton Hills, Ontario
Frank Default
 

Fuel pressure spec is 51 psi and the pressure should be > 29 psi after 30 minutes. If the measured fuel pressure is higher than spec, I would expect negative fuel trims, not positive. As al ready suggested a WOT fuel pressure test (with gauge in sight) would confirm or eliminate the fuel pump.

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Joe Technician
Hamden, Connecticut
Joe Update
 

Customer needed vehicle so just got back to it today. After verifying good pressure and volume from pump under wot I pulled injectors and did a quick flow Test. 10 to 15 seconds of cranking with injectors into containers revealed 3cc from one injector, 1cc from two and 2cc from the other. Clearly an injector flow issue. Replaced injectors and took care of problem.

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