how to inspect O2 sensors?

[RyanHeo]

Hi, guys.

I replaced all the O2 sensors to 96' Infiniti I30 about 4 months ago. Those were all NTKs. After the sensors replaced, the gas mileage was up to 330 miles per 16 gal in the city driving. However these days are 250 miles per 16 gal. in the city and even 320 miles on the highway. So I would like to check the O2 sensor even though it haven't come CEL up.

Thanks.

 

[alreadygone]

Guess you could pull them out and do a visual. My guess though, would be they'll throw a code long before you could actually see anything. Probably a nonrelated issue. What about plugs? Wires? fuel filter?cat converter? etc.

Bob

 

[Dad2leia]

Not only the parts that alreadygone mentioned, but don't forget, we northerns are already in highly oxygenated fuel season, which lowers mileage.

 

[MaximaGuy]

I thought the VQ3.0 was rated at 21-22 city and 25-26 highway MPG. You are getting that, so I wouldn't worry. I would go for a fuel injection tuneup, see if the ignition coils need replacement, balance and align wheels, raise the PSI front to 38 front and 36 rear. Since you live in a cold env, tire pressure won't rise beyond 38 psi even when the tires are hot.

Good luck.

 

[MaximaGuy]

I thought the VQ3.0 was rated at 21-22 city and 25-26 highway MPG. You are getting way below that, so I would worry.

Why is the edit option not provided? sucks.

 

[benjamming]

Quote:

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Why is the edit option not provided? sucks.

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Edit function work-around

 

[MaximaGuy]

Super, I shall use this in future.!!! Thx benjamming.

 

[RyanHeo]

I replaced 5 ignition coils, air filter, spark plugs, and fuel filter even alignment but it still below the 16 miles.

 

[mechtech2]

Cool weather will drop mileage.
But are there any codes? How about a free scan at Autozone?
Remember that an O2 code doesn't mean that the O2 sensor is CAUSING leanness/richness, but READING leanness/richness.

 

[Ramjet Roger]

I have an OBDII software package called Autotap installed on my laptop that enables me to read the the OBDII information. I noticed that the readouts include O2 Sensor voltages. I saw another post on this forum where the poster indicated that an O2 sensor voltage should read between .1 to 1.0. As long as it's in this range, the sensor is still considered good. I verified that one of the diagnostic tests described in my Ram 1500 service manual says to verify the voltage is in this range. Might be a quick way to see if they're still good.

One lesson I learned recently (documented in my ...Timing Belt Failure... post) is that a P1072 CEL (running too rich) may in fact be due to a valve timing problem or fuel pressure to high. The sensor was reporting the correct condition. I thought I'd fix it by replacing the messenger (the O2 sensor in this case). In reality, it was something else altogether.

 

[brianl703]

If an oxygen sensor is reporting that the engine is running too rich it is almost never the oxygen sensor at fault! The reason is that the sensor has to produce a voltage above about .45 volts in order to signal a rich condition.

A failed oxygen sensor outputs a very low, or no, voltage and that is interpreted as a lean condition.