# 200sx se-r avg. 12 mpg - need help!!!!



## crazy200sx (Dec 16, 2004)

Hi, I just bought a 1996 Nissan 200sx se-r (2.0 L 16valve 5 speed tranny). Everything seems to work fine except the speed sensor and the very low millage I get - avg. 12 mpg (regular driving)

I just did a tune up and also change oxygen sensor and a cooling temp sensor, but it didn't help a lot?

What should i check?


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## pc080189 (Jun 7, 2002)

There are 2 gas mileage threads on the first page of the B13 section.
Both should be able to help you a bit.


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## lshadoff (Nov 26, 2002)

crazy200sx said:


> Hi, I just bought a 1996 Nissan 200sx se-r (2.0 L 16valve 5 speed tranny). Everything seems to work fine except the speed sensor and the very low millage I get - avg. 12 mpg (regular driving)
> 
> I just did a tune up and also change oxygen sensor and a cooling temp sensor, but it didn't help a lot?
> 
> What should i check?


What did you do for the tune up? It should be spark plugs (NGK), check plug wires, check distributor cap, timing (17*) and idle set, and fuel filter. 

You should check for vacuum leaks (cracked hoses, disconnected hoses). 

Is the Check Engine light on? If so, what is the code? 

The speed sensor is one of the sensors used in setting the Air-Fuel ratio. If it is malfunctioning, the ECU is probably in open-loop control, and not relying on the front O2 sensor. 

Lew


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## crazy200sx (Dec 16, 2004)

Thank you guys, I changed spark plugs (NGK) and wires (NGK) , distributor cap and rotor, fuel and air filter, as well as cooling temp. sensor and O2 sensor. 
The code of error is 014? and the mechanic said that it's fault of the speed sensor. I don't know how bad is the sensor, but my speedometer sometimes works (few miles) than it doesn't (another few). I ordered already one and i hope it will solve the problem.

My first mechanic said that there is something wrong with knock sensor, but that was before the tune up. After some time i went to the other mechanic who said that for him the knock sensor works fine; however, he said something about exhaust leaking and suggested change of back muffler. For me everything is fine with the exhaust and I don't believe it could change that much in fuel use (from 12 to 28 mpg).


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## lshadoff (Nov 26, 2002)

crazy200sx said:


> however, he said something about exhaust leaking and suggested change of back muffler. For me everything is fine with the exhaust and I don't believe it could change that much in fuel use (from 12 to 28 mpg).


An exhaust leak can effect the O2 sensor. If extra air leaks into the exhaust system, the O2 sensor thinks the mixture is too lean, and enriches it. This will cause a loss in gas mileage and spark plug fouling (black residue).

Lew


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## crazy200sx (Dec 16, 2004)

how can I find the leaks? Do I have to change the whole exhaust (headers, resonator, cat conv and muffler)? 
Is there any cheaper way to fix a leak?


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## himbo (Sep 20, 2003)

sure, go to your local auto parts store, and they should have an exhaust repair kit. i used one on my old school '85 manure brown Camry. basically, its special tape, and you cut a piece of aluminun (from a soda can), attach the aluminum by wrapping the tape over the exhaust, and turn on the can and let it run for a little while. that will melt the tape over aluminum piece and exhaust and it should hold it for a while. its half assed for sure, but a decent temporary fix!


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## lshadoff (Nov 26, 2002)

crazy200sx said:


> how can I find the leaks? Do I have to change the whole exhaust (headers, resonator, cat conv and muffler)?
> Is there any cheaper way to fix a leak?


You can hear leaks if they are before the muffler (which is just about the whole exhaust system). Just let the car idle and listen under the hood for an exhaust sound in the front of the engine. Then follow the exhaust pipe down the passenger side listening for it. Also you should hear it when driving at a slow steady speed or slightly accelerating with the windows open, but you won't know where, exactly, it is.

Lew


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## crazy200sx (Dec 16, 2004)

One more thing, in the current cat converter there is a sensor placed in the middle of it. 
If i want to install a universal cat converter, should i place this sensor before or after the cat conv?


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## crazy200sx (Dec 16, 2004)

Today i went to the shop and the mechanic welded the cracked pipe and he said that the muffler and cat converter are in good shape- and the use of gas didn't decrease. 
Because I changed the o2 sensor and did a complete tune up I hope that the last thing i would have to change is speed sensor and knock sensor.

Please tell me if i need to know anything important about changing those two sensors. Do I need to go to the mechanic to restart the timming to it's factory settings??
Does speed sensor affect the gas millage? (mine sometimes work, sometimes not).


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## nova73guy (Mar 30, 2004)

not sure about the speed sensor, but don't overtighten the knock sensor. Made that mistake and had to buy a second replacement.


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## sersr20dk (Oct 15, 2003)

it is probably the speed sensor causing the problem. you should try resetting the ecu and see if you don't get better mileage because of the fuel trims and bad habbits the ecu picked up will be cleared. if you don't find the problem it will come back. check the tps also just to be sure. any driveabiltiy concerns? with that bad of gas mileage it has to drive different.


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## crazy200sx (Dec 16, 2004)

It doesn't have a power up to 2,500 rpm (it's shaking and chocking), after that it starts to accelerate.

How can I restart the timing to the factory settings? Does it change by itself when I instal new knock sensor?
And how can I reset the ECU?


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