# 94 Altima 18 mpg or less horrible gas mileage



## jordancrockett (Dec 23, 2007)

Alright, I have a 94 Altima that has been in my family forever, and so now I am stuck with doing all the work into fixing it up. A couple years ago when my sister had it, it was solid at 26-28 mpg, but now its running as low as 18 mpg going down the highway. 

I have ran a compression test and it came out green, I have checked my Knock Sensor and its fine, can't be the O2 sensor because I just passed an emission test with flying colors not a month ago, a have a new exhaust system, new distributor with what i hope to be perfect timing, runs great and sounds great, and its not spittin any kind of smoke that is irregular. I have checked my onboard diagnostic's and it comes out 55, all clear. 

If anyone has ANY idea as to why it would run so bad, please give me all of the advice you have! ha. 

Thanks a million.


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## Ripper65 (Jan 23, 2008)

Timing can give you BAD gas mileage. Might want to check that. If you got a new distributor you should have set the timing too.


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## Altima SSS (Oct 10, 2007)

To get that bad of gas mileage, it's got to be running way too rich. I'd double check the timing like Ripper said, and also check the coolant temp sensor.

There are two coolant temp sensors located next to each other on the back upper right hand side of the head area. One sensor is for the ECU input and the other is for the dash gauge.

http://www.autozone.com/az/cds/en_us/0900823d/80/1b/61/d2/0900823d801b61d2/repairInfoPages.htm

If the one for the ECU input is bad, it could make the ECU put too much fuel in and make the MPG go way down. You might also pull a spark plug or two and see if they look rich.


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## SkunkWorks (Nov 4, 2007)

How can I check the timing on the 1st gens?


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## jordancrockett (Dec 23, 2007)

the plugs aren't bad i'm sure. but i will check out that coolent temp sensor problem.


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## jordancrockett (Dec 23, 2007)

oh also, that sensor problem would throw a trouble code, but i have been at a steady code 55 for some time, so should i still check if nothing is wrong?


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## Altima SSS (Oct 10, 2007)

jordancrockett said:


> oh also, that sensor problem would throw a trouble code, but i have been at a steady code 55 for some time, so should i still check if nothing is wrong?


True ... code 13.
http://www.autozone.com/images/cds/gif/large/0900823d801b6297.gif

But, it will only trip a code if it's a hard failure ... open or shorted circuit. If the sensor is degraded and the output is heavily skewed than it will not throw a code. The resistance check vs. temperature is the real test on this one.









Large version: http://www.autozone.com/images/cds/gif/large/0900823d801b61d4.gif

Easiest check is to pull the connector off right after the engine has been stopped and check the resistance. The sensor should be close to the 194 deg F test point when the engine is at full operating temperature. Could also check when the engine is fully cold to get the low end resistance and make sure it's close to what's listed in the table.


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## jordancrockett (Dec 23, 2007)

so it could quite possibly be that. i checked it after hot and it was running at 1.3k ohms when it should be somewhere around 200 ohms, so I think it might be that. thanks! I will write back after i get it fixed.


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## Altima SSS (Oct 10, 2007)

jordancrockett said:


> so it could quite possibly be that. i checked it after hot and it was running at 1.3k ohms when it should be somewhere around 200 ohms, so I think it might be that. thanks! I will write back after i get it fixed.


Yep, sure sounds like it could be the problem. If the coolant sensor is running at 1.3K ohms, then the ECU thinks the engine is still cold and running it too rich.

Let us know how it comes out!


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## jordancrockett (Dec 23, 2007)

alright so false alarm, me being a renab checked the sensor going to the ECM, not the actual sensor itself that is in the engine. I checked that and it came out at 230ish Ohms, so that can't be it. I don't know what else to check.


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