Mitsubishi Repair: Eclipse getting REALLY low mpg!, white arrow, intake hose

Question
Hi Anthony,

I just purchased my fifth Eclipse, a '97 Coupe. The only problem is, it's getting about 10-15mpg.

The previous owner has installed a makeshift short ram intake. Here are some detailed pictures of the engine:

http://www.tccommerce.com/1.jpg
http://www.tccommerce.com/2.jpg
http://www.tccommerce.com/3.jpg
http://www.tccommerce.com/4.jpg
http://www.tccommerce.com/images/filter.jpg
http://www.tccommerce.com/images/pipe.jpg
http://www.tccommerce.com/images/inside.jpg
http://www.tccommerce.com/images/mystery.JPG

(In the last photo - isn't something supposed to connect to the bottom of the intake hose there?)

I'm told that the little valve to which I have a white arrow pointing in one of the pictures should be connecting into the intake hose, and there is a little bit of suction there even when idling. Someone said this is very likely the problem.

The seller has apparently disabled the check engine light. Here are the results of a diagnostic run tonight:

DTC (Codes)

P1698
Manufacurer Contrl.
Auxiliary Inputs
Auxiliary Outputs

P1899
Manufacurer Contrl.
Transmission

P0171
System Too Lean (Bank 1)


Here is what I've done so far:

1. Tightened what were loose connections between the intake hose, blue hose pictured, and the filter

2. Reset the ECU by removing negative connector and turning to "On"

Mileage is still in the basement...any help is appreciated.

Answer
Nathan,
The little tube coming off the valve cover that is supposed to be connected to the intake tube is the breather.  It's not what is causing your low mileage.  Many people do disconnect that hose, but you never want to leave it sucking in unfiltered air.  You should put a little breather filter on it, else connect it back to the intake hose.

As for the intake hose itself, it looks like a "Frankenstein upgrade".  It appears as a random intake hose (maybe from a stock turbo model Eclipse) was slapped onto that car in hopes of increased performance.  In reality, it may be causing serious damage to the car.  That 'mystery' opening in the tube is sucking in unmeasured, and what's worse, UNFILTERED air into the engine.  This is causing the lean DTC to be thrown.  This is really confusing your car's computer and could have worn out the O2 sensor.  Either of which could be causing your poor gas mileage.  Hopefully you don't find any other haphazard upgrades the previous owner attempted.  

My recommendation would be to find a stock intake hose that is used for your car.  I bet you'll be able to find one real cheap on eBay.  Else, you may want to find a cold air intake that is made specific for your car.
Good luck!