Question about 2002 Nissan Altima

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Poor fuel economay, fuel mixture to rich - 2002 Nissan Altima

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  • g_cossman Aug 05, 2008

    have a check engine light on according to that it is one of two oxygen sensors, or an air flow sensor. What the problem is so I don't have to fix unnecessary things

  • bevers71 Aug 05, 2008

    Check Engine Light (CEL) on intermittently on my 1995 Quest, usually coming on in a longer uphill grade, and performance (power) seems to be less than normal. CEL then goes out shortly thereafter on level road. OBD-1 shows code 33- oxygen sensor and 34- knock sensor.
    Is there any way of knowing if the knock sensor is a result of the oxygen sensor? Is it worth just replacing the oxygen sensor, then reset CEL, without the much more complicated (&/or expensive) knock sensor replacement?
    Any secrets to replacing the sensors not already in the Haynes manual?


  • Anonymous Aug 20, 2008

    My check engine light is on and its the oxygen sensor how important is that sensor?

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Knock sensor will not illuminate the chacke engine light. replace the 02 sensor and see what happens. have/check the harness going into the sensor. those wires brake inside the shielding . make sure its all intact/the harness.

Posted on Sep 01, 2008

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  • Expert
  • 97 Answers

The upstream sensor is the probable cause (ahead of catalytic converter)

Posted on Aug 05, 2008

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1 Answer

Engine knocking at startup


bad air/fuel mixture could cause rod knock like that, which is a for of backlash or whip like action. Detonation, like very poor grade of fuel. IF your engineis running really rich, the extra rich fuel goes by your piston rings and thins out your engine oil. If you have a bad ROD bearing, it is probably TOO LATE. CLEAN YOUR THROTTLE BODY and IAC valve, since these things fine tune your FUEL/AIR mixture and PREVENT rich running. GOOD LUCK!!

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Engine skips after it gets warm


if it does not need a tuneup, then I would say to check the coolant tempurature sensor. if bad it will result in. poor cold idle, stalling, rich mixture and ******** timing, slow idle speed, cold hesitation, stumble, poor fuel milage. good-day! if need be. change plugs and wires first ! this could also be your problem.

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2002 pt cruiser code p0172


DTC P0172 - P0172 Fuel Trim System Rich Bank 1... this indicates that the fuel mixture is too rich, but you already know it is running rich.

A rich fuel mixture can be caused by a number of things First, I would suggest checking fuel pressure to make sure it is within normal specs If fuel pressure is too high due to a faulty pressure regulator for example, it will cause too much fuel to be entering the engine.

A leaking fuel injector can cause a rich fuel mixture, as can an injector that is stuck in the open position. When the engine is shut off, monitor fuel pressure with a fuel pressur gauge; it should remain steady.If fuel presure drops when the engine is off, then removing the fuel rail and injectors while still connected to the lines to visually check for a dripping injector may be informative.

There are several engine control system problems that can cause a rich fuel mixture; if you can obtain a scan tool that is capable of displaying live engine data you can check for these possible causes:

1) Low MAP reading; this can be due to a fault in the MAP sensor, MAP circuit, or as a result of low engine vacuum due to a restricted exhaust, jumped timing belt, or low compression on one or more cylinders caused by valve leakage or a leaking head gasket. Compression testing the engine may reveal internal mechanical problems of this type that would cause low engine vacuum. A low engine vacuum reading from the MAP makes the computer think the engine is under heavy load such as during acceleration, so it commands a rich fuel mixture in response. A vacuum leak can also result in a rich mixture for the same reason.

2) Low coolant temperature signal. This can be caused by a fault in the coolant temperature sensor circuit, faulty coolant temperature sensor, low engine coolant level, or a faulty thermostat that is allowing the engine to run too cold.

Keep us updated.

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1996 camero v8, after running car and it gets warmed up it quits runnung, after it cools off it starts with no problem??


check your coolant tempurature sensor. sounds like the symtoms of a bad sensor.--- poor cold idle, stalling, ( rich mixture) retarded timing, slow idle speed, cold hesitation or stumble, poor fuel milage, will also ****** timing. hope this helps!

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1 Answer

Not picking up gas when engine is cold, sputtering, bogging out especially when travelling uphill, Is this some sort of a sensor maybe??,the spark plugs are new. thanks


check fuel filter. it is starving for fuel. unless the fuel pump is bad. check filter first, then go from there. symtoms of a bad coolant sensor--poor cold idle, stalling, rich mixture retarded timing, slow idle speed, cold hesitation or stumble, poor fuel milage.

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1 Answer

Major hesitation at cold idle, car accelerates at a slow pace, hesitation also appears when in passing gear. replaced fuel filter 2 months ago


symtoms of a bad coolant sensor: poor car idle, rich mixture, retarded timing, slow idle speed, cold hesitation or stumble, poor fuel milage, check and make sure air filter is clean. and check plugs and wires if need be,

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1 Answer

1987 Dodge Caravan getting poor gas milage


If you suddenly are getting poor gas mileage your O2 (oxygen) sensor may have failed. The O2 sensor helps dictate how rich or lean the fuel mixture is. If it fails the engine's computer defaults to a rich mixture so not to burn a valve or run too hit. This can be checked and if need be easily replaced. And yes if the van is over-do for a routine tune-up this is always a good investment. Make sure to check the air filter too, if she's dirty the engine will starve for air and get poor mileage.

I hope this may have assited you,
Tom

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1 Answer

Replacement of o2 sensor


Every new car, and most cars produced after 1980, have an oxygen sensor. The sensor is part of the emissions control system and feeds data to the engine management computer. The goal of the sensor is to help the engine run as efficiently as possible and also to produce as few emissions as possible.
A gasoline engine burns gasoline in the presence of oxygen (see How Car Engines Work for complete details). It turns out that there is a particular ratio of air and gasoline that is "perfect," and that ratio is 14.7:1 (different fuels have different perfect ratios -- the ratio depends on the amount of hydrogen and carbon found in a given amount of fuel). If there is less air than this perfect ratio, then there will be fuel left over after combustion. This is called a rich mixture. Rich mixtures are bad because the unburned fuel creates pollution. If there is more air than this perfect ratio, then there is excess oxygen. This is called a lean mixture. A lean mixture tends to produce more nitrogen-oxide pollutants, and, in some cases, it can cause poor performance and even engine damage.
The oxygen sensor is positioned in the exhaust pipe and can detect rich and lean mixtures. The mechanism in most sensors involves a chemical reaction that generates a voltage (see the patents below for details). The engine's computer looks at the voltage to determine if the mixture is rich or lean, and adjusts the amount of fuel entering the engine accordingly.
The reason why the engine needs the oxygen sensor is because the amount of oxygen that the engine can pull in depends on all sorts of things, such as the altitude, the temperature of the air, the temperature of the engine, the barometric pressure, the load on the engine, etc.
When the oxygen sensor fails, the computer can no longer sense the air/fuel ratio, so it ends up guessing. Your car performs poorly and uses more fuel than it needs to.
More to come soon! presently looking for detail instruction on how to repair or replace.
I found this link with info on the sensor .... might be helpful

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