# Un-Burned Gas Smell from exhaust



## jolak (Feb 16, 2005)

Experts,
I got P0100 from my 1998 Nissan Altima (74k miles). Replaces the MAFS. Reset the ECM by turning the ECM and by removing the battery negative did not work. Cleared the code using Reader at AutoZone for free. Now the car runs fine. But the Smell from the exhaust seem like it is not burning the gas well. Does anybody know what the problem is?


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## Marvin (Oct 16, 2002)

jolak said:


> Experts,
> I got P0100 from my 1998 Nissan Altima (74k miles). Replaces the MAFS. Reset the ECM by turning the ECM and by removing the battery negative did not work. Cleared the code using Reader at AutoZone for free. Now the car runs fine. But the Smell from the exhaust seem like it is not burning the gas well. Does anybody know what the problem is?



Do you have an aftermarket exhaust?


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## jolak (Feb 16, 2005)

Mark said:


> Do you have an aftermarket exhaust?


Thanks for you reply. I did not do anything to my Exhaust since i bought the car brand new. What do you mean by aftermarket exhaust ? BTW, the MAFS i bought was used @ 38k miles.


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## Marvin (Oct 16, 2002)

jolak said:


> Thanks for you reply. I did not do anything to my Exhaust since i bought the car brand new. What do you mean by aftermarket exhaust ? BTW, the MAFS i bought was used @ 38k miles.



When you install an aftermarket (read: high performance) header or exhaust, it allows unburned gas to escape all the way through the muffler. Or if you take out a catalytic converter, you get the same result.

It may be that your car is running rich with fuel and the MAF is sending too much in and its not being used. I think you might have to take it in to get it tuned to a good mix of gas vs. air.


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## jolak (Feb 16, 2005)

Mark said:


> When you install an aftermarket (read: high performance) header or exhaust, it allows unburned gas to escape all the way through the muffler. Or if you take out a catalytic converter, you get the same result.
> 
> It may be that your car is running rich with fuel and the MAF is sending too much in and its not being used. I think you might have to take it in to get it tuned to a good mix of gas vs. air.


Thnaks. I just did a 75k miles servicing before i changed the MAF. 
Ok. I will try the tuning next. One more question, if i don't tune my gas Vs air mix , Am i going to fail state inspection which is coming in June 2005 ?


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## jolak (Feb 16, 2005)

Mark said:


> When you install an aftermarket (read: high performance) header or exhaust, it allows unburned gas to escape all the way through the muffler. Or if you take out a catalytic converter, you get the same result.
> 
> It may be that your car is running rich with fuel and the MAF is sending too much in and its not being used. I think you might have to take it in to get it tuned to a good mix of gas vs. air.


Mark, now I remember. After I replaced my MAF, I checked the voltage coming out of MAF when the engine is not running, idle, running and running at higher RPM. I got little more voltage that it was mentioned in Haynes book.

Can I do the tuning myself or I have to take it to the shop?

Thanks again.


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## Marvin (Oct 16, 2002)

There is an extremely good chance that you will fail.

Now that I think about it, the ECU should change the air vs. gas ratio on its own.


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## jolak (Feb 16, 2005)

Mark said:


> There is an extremely good chance that you will fail.
> 
> Now that I think about it, the ECU should change the air vs. gas ratio on its own.


Mark, I appreciate your help. I will keep you posted.


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