# 2001 Sentra still stuttering and bad MPG



## Dagolfer (Dec 5, 2013)

Initially I had great gas mileage but the only problem I was having was that the car was shutting off at low rpms.

I went in and had the plugs, O2 sensors, wires all changed

After that my sentra stuttered like crazy and had low power and pickup problems. I had a fuel too rich code that popped up

I also had problem with an exhaust smell coming from the front of the car and my MPG has dropped from near 30 to around 20

Since then I have

1)Changed the MAF
2)Cleaned the IAC
3)Cleaned the EGR

Now I have no codes (I did not reset anything, it just went away)
My MPGs are still very bad and I have a horrible stutter around 3rd and 4th gear.

I guess my question is, should I change the EGR? Or should is there anything else I should check first?

Thanks!


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## b13er (Apr 7, 2010)

Fuel too rich makes me think you might have a spark problem. So what kind of plugs did you just put in the car? Hopefully NGK's.

Considering they just changed the O2 sensor and now you smell exhaust at the front of the car, makes me think your O2 sensor didn't seal right. Often times you go to fix something on the car and create another new problem.

I don't think you should change the EGR, just test it. Just watch some youtube videos on it, or read how in the Haynes manual. Or instead of buying a new one, just make a block off plate out of a coke can, and if it solves your problem then you know the problem is with your egr. I saw that tip in a youtube video and thought it was genius.


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## Dagolfer (Dec 5, 2013)

b13er said:


> Fuel too rich makes me think you might have a spark problem. So what kind of plugs did you just put in the car? Hopefully NGK's.
> 
> Considering they just changed the O2 sensor and now you smell exhaust at the front of the car, makes me think your O2 sensor didn't seal right. Often times you go to fix something on the car and create another new problem.
> 
> I don't think you should change the EGR, just test it. Just watch some youtube videos on it, or read how in the Haynes manual. Or instead of buying a new one, just make a block off plate out of a coke can, and if it solves your problem then you know the problem is with your egr. I saw that tip in a youtube video and thought it was genius.


All I know is they were expensive...titanium? 

How do I go about testing a seal of an o2 sensor?

Oh and a new symptom has arrisen. I don't know if this is just from all the stuttering knocking something loose, but now I am hearing a rattling sound that wasn't there before the stuttering. It's on the right side of my car, which is making me believe it has to do with something loose with the exhaust. I am hoping that it's just a loose plate.

Thanks!


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## b13er (Apr 7, 2010)

Dagolfer said:


> All I know is they were expensive...titanium?
> 
> How do I go about testing a seal of an o2 sensor?
> 
> ...


Well you need to find out what kind of spark plugs are in there because you said it's running worse after you changed those parts. I have heard one too many stories about people putting Bosch platinum 4's in their car and then the car ran like complete crap. You should have the NGK Laser Platinums in there, that is the stock plug, here is the model number: PLFR5A-11 and they should be gapped to .043 inches. If that's not what you have, then try taking your current ones back(just say they didn't work with your car) and getting the right ones.

Usually the rattling is a loose catalytic converter shield, I always just pull mine off. They are supposed to reduce the chance of catching a field with tall grass on fire, but I hardly doubt it would even work.

For exhaust leaks, attach a piece of tissue paper to a stick, and hold the tissue in places you think might be leaking. If it's leaking the tissue will be waving around and it will be obvious.

If the O2 sensor really is leaking air, that's rare, but you could try tightening it down more. Or uninstall it, clean the mating surface, and look for cracks(maybe someone overtightened it and cracked the exhaust manifold).

While the car is still running, I would take it to an autoparts store like Autozone and have them hook a computer up to it and see if there are any trouble codes(that's free btw). That should be the first step to diagnosing a problem with your car.


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## Dagolfer (Dec 5, 2013)

Update: Please help

Ok so my car finally tripped a SES code and it came back with a thermostat. After changing the thermostate the MPGs are still bad, it stutters during idle and in 3rd and 4th gear and I have a loss of power and surge. To get rid of the stutter I either have to take my foot off the gas and apply more pressure or shift up.

What could my garage have done when changing my 02 sensors that could have caused this?

So basically here is the timeline

Car was turning off at low RPMS
Changed the 02 sensors, wires, plugs
Car started with powerloss/surge symptoms
Took it in and asked for a vaccuum, compression test (don't know if this was actually done)
Changed an apparent bad 02 sensor
Car worked better but still had a hint of a powerloss and surge
Stuttering appeared and idle got worse within a week of 2nd 02 sensor change
Since then I have:
Cleaned the IAC
Changed MAF
Cleaned Throttle body
Cleaned EGR Sensor
Replaced Thermostat
Ran a some Techron through the gas tank

So thinking back the problem seems to have happened after they changed my O2 sensor.

Could the garage have done something that would have caused all this mess?


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## rogoman (Dec 16, 2004)

What engine is in your car?


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## Dagolfer (Dec 5, 2013)

rogoman said:


> What engine is in your car?


1.8 L with 170k miles


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