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Discussion Starter #1 (Edited)
Hey everyone, first post here!

I have a 2005 hatch with the 2.3l engine and manual transmission. For the last few months, I've been playing parts-darts trying to improve the MPG of my car. When I bought it last year, I was getting close to the 22/29 factory rating. Since around last winter though, I've only been able to get about 18/25 at best. Is this somehow normal for a car of this age, or am I right in trying to fix it?

So far, I've tried...
>New ignition coils
>New spark plugs
>Compression test (all [email protected])
>Cleaning the MAP sensor
>Cleaning the fuel injectors
>Upping my tire pressure
>Not driving like a child

The engine has been well maintained, has only 130k miles, and still has plenty of power. The only thing I will say is that twice now I've gotten a check engine light for a random misfire. It never feels like its misfiring, and after clearing the code it stays gone for months.

I'm really hoping this is a common problem, as it seems like MPG is a common topic around here. I'm getting to my wits end with this car, and would really hate to have to sell it. I'm kinda sick of just dumping in money though. Any feedback is appreciated!
 

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I have not, as I don't know how...
You would need to get an OBD realtime data stream reader (not just a code reader). There are commercial units for sale off-the-shelf, or you can get a phone app, such as the popular Torque for Android (however there are many others as well).

Once you have the reader, all you need to do is plug it in and watch the data values on the display. Along with other potentially helpful data, fuel trims will tell you about the vehicle's fuel management and if it's running consistently rich or lean.
 

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Discussion Starter #5
You would need to get an OBD realtime data stream reader (not just a code reader). There are commercial units for sale off-the-shelf, or you can get a phone app, such as the popular Torque for Android (however there are many others as well).

Once you have the reader, all you need to do is plug it in and watch the data values on the display. Along with other potentially helpful data, fuel trims will tell you about the vehicle's fuel management and if it's running consistently rich or lean.
Oh cool. I actually do have a bluetooth OBD2 reader that I think shows some other data through the phone app. I'll have to check it out. I've only ever used it for codes!
 

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Odds on bet, if the fuel trims look off, your upstream O2 sensor has gone Tango Uniform.
 

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Discussion Starter #7
I suppose I should provide an update to this for anyone with a similar issue.

When I originally made this post I had put 50 miles on my first tank of gas after getting my injectors cleaned. My gas gauge was going down at an alarming rate, so I got worried and decided to finally start this thread about it. Shortly after driving around some more, my gauge stopped at around half and stayed there for around 60 miles. This put my current tank back on track to get decent mileage, and so I rode it out and eventually got about 265 miles from it. My mileage ended up being right around 23, which was mostly city with a tiny bit of highway. This is on par with the EPA suggested mileage, and so my issue was solved!

To anyone else experiencing this, get your injectors cleaned! I found a local fuel injection shop and they only charged me $65 to clean all four. This cleaning was able to fix one injector that they said was leaking out more gas than it's meant to, which was likely my problem.
 
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