# Engine Running Lean



## Squid11 (May 1, 2006)

My 2000 Maxima SE had its SES light go on yesterday, and when I scanned it, the code was P1071, for too lean. I know that can mean a million things from a dirty MAF sensor to clogged injectors to a bad O2 sensor, but I was wondering if anyone has had this code before, and what you looked for first. Thanks! :newbie:


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## Jeff (Oct 17, 2002)

I would just check the normal stuff as they are the cheapest before you go into replacing injectors or whatever.

When was the last tune-up?
When did you last change the fuel filter?


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## Squid11 (May 1, 2006)

Last tune up was at 90,xxx miles. It has 94, xxx on it now.
I have no idea when the fuel filter was last changed. That'd probably be a good place to start. Unfortunately, I know nothing about the fuel filter on the car. I've changed the fuel filters on my diesel truck for awhile now, and it's in a very accessable position (top of engine valley). Where is it on the VQ?


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## DylanDET1 (Apr 28, 2006)

2000 while older now is a relativley new car.... i had a 97 at one point that would trip CEL for mediocre reasons.... engine misfire and lean codes are often set for fuel reasons... my car ran perfect but on ocasion id try and save money at the pump with 87 "getty" fuel and it would set the light off, a nissan machnic friend of mine told me it happens alot because of poor fuel, theres no need to run 93 but during the winter especially gas has extra aditives in it that lower the quality, he also suggested to get gas from mobil or hess stations rather then ur "arab" mart (no offensense ment), u should probably check ur plugs for indications of lean burn and replace, also check for a cloged air filter wich could restrict air/fuel mixture and trick ur MAF, listen for any leaks taht allow air to bypass ur MAF, but thats only a precaution, throw in a bottle of injector cleaner or have them sonic cleaned at a shop for 70 bucks, if it pursists try a higher octane and have ur ecu cleared of all codes as they are stored in some models after the light goes out.. luck


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## Jeff (Oct 17, 2002)

I don't agree with using less than Premium fuel for the Maxima.

The Maxima engine's compression is set really high and _especially_ during the summer you are more susceptible to experiencing knock with lower grades.

Not only will you experience knock but the engine will compensate by running more 'rich' and thus reducing your miles per gallon. In the end, the cost for running premium and low-grade fuel are just about the same price.


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## Squid11 (May 1, 2006)

Jeff said:


> I don't agree with using less than Premium fuel for the Maxima.
> 
> The Maxima engine's compression is set really high and _especially_ during the summer you are more susceptible to experiencing knock with lower grades.
> 
> Not only will you experience knock but the engine will compensate by running more 'rich' and thus reducing your miles per gallon. In the end, the cost for running premium and low-grade fuel are just about the same price.


Pardon my ignorance for a bit, but doesn't the engine have aluminum heads and an iron block? Plus, when this was happening, the ambient temperature was only around 65*, so I don't think excessive heat would be causing premature detonation, even if the fuel that I got had a lower octane rating than I thought. 

I think I'm going to try to find the fuel filter and change that out, then try cleaning out the MAF....I'd rather not have the stealership charge me 85$ to throw it on their diagnostic computer only to tell me I have somethign stupid like a vacuum leak.


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## Jeff (Oct 17, 2002)

Squid11 said:


> Pardon my ignorance for a bit, but doesn't the engine have aluminum heads and an iron block? Plus, when this was happening, the ambient temperature was only around 65*, so I don't think excessive heat would be causing premature detonation, even if the fuel that I got had a lower octane rating than I thought.


I don't know what significance the type of metal that is used in the engine has to do with knock. Lower octane doesn't burn as good as premium. I found this on a website:

"_When knock occurs, there is uncontrolled combustion with multiple flame fronts, with only one of them being initiated by the spark plug. During knock, cylinder pressures experience an extremely rapid rise and spontaneous burning and release of the end gases' energy. It is not uncommon to see a pressure rise of up to 8 bars per degree of crankshaft angle, or up to 50,000 bars per second...
...As stated earlier, anything that will raise temperatures in the cylinder will help promote detonation. This rise in temperature could occur many different ways: very lean air/fuel ratios, heating of the charge air prior to entering the combustion chamber, compression of the air molecules from forced induction, or poor heat dissipation through the cooling system. Increase of cylinder pressure will also prompt detonation. Camshaft profile, compression ratio and quench area all come into play. Design criteria as to combustion chamber shape and mixture motion, spark plug location and piston design can all make an engine more or less inherently prone to abnormal combustion. Naturally, spark timing and fuel quality round off the list._"


> I think I'm going to try to find the fuel filter and change that out, then try cleaning out the MAF....I'd rather not have the stealership charge me 85$ to throw it on their diagnostic computer only to tell me I have somethign stupid like a vacuum leak.


Definitely the BEST idea...


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## DylanDET1 (Apr 28, 2006)

how would u go about cleaning ur MAF.. its a small filimant similar to a light bulb the passing air cools the filament sending volatge readings to the ecu telling it how much air passed through.... check ur voltage reading from the maf sensor line to see if its in the right range is the best thing to see if it is functioning properly, check in ur area if a local parts store will do it free of charge, autozone checks all ob2 and lists problem codes and resets it free


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## Jeff (Oct 17, 2002)

You can clean the MAF sensor with an electrical contact cleaner...or you could try using rubbing alcohol on a q-tip (GENTLY) rubbing the sensor clean.

Just make sure it is dry before starting the car...(which shouldn't be a problem using either of the above methods)


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