Mitsubishi Repair: 98 Mitsubishi eclipse spyder convertible 2.4, mass air sensor, barometric pressure sensor

Question
Hello.  I bought this car a week ago with 82000 miles on it, so i figured it would be good.  did seem to hesitate a bit, but the salesman told me that it was due to the aftermarket cold air intake that was put on and it makes it run a little rough in the cold.  Well, i have changed spark plugs, messed with the air intake, recharged the filter and nothing worked.  it idled rough too, so i unhooked the vacume from the EGR and the idle went to 1500rpm and ran steady and smooth.  So one part maybe fixed.  i have been running her without the egr on for a couple days unil i can get a new one.  But i still have a problem with hesitation.  when i step hard on the gas, she bogs down.  i have to feather the gas, but once she goes...she goes.  the other thing i noticed is the downshifting, slams pretty hard sometimes and feels like the back axle was tied to a tree, and then other times she shifts down easily.

well, took it in to put the computer on it.  codes are P0105 and P0400.  what now?  I think the P0105 is the EGR, but what the heck is the 0400 (barametric pressure sensor???) how do i fix that and is that the hesitation problem?

Answer
Cody,
The barometric pressure sensor is part of your mass air sensor (MAS), that also includes a flow sensor and the IAT sensor (intake air temperature).  If the MAS was damaged or modified with the installation of the cold air intake, that can definitely cause the problem you're experiencing.  When more air enters the engine than the ECM (car's computer) is expecting, it retards the ignition timing and puts an increased strain on the fuel pump.  If air-to-fuel ratio is too lean (too much air), then detonation can occurs, which can severely damage internal engine components.  You can try to replace the fuel filter, to be sure that is as clear as possible to prevent any fuel supply restrictions.  Also try using premium fuel, which burns hotter, more completely, and helps prevent engine knock.

As a last resort, you may want to try to find the original intake components and remove the cold air intake.  In reality, you may only be gaining an additional 5 HP or less at the wheels with a cold air intake.  In my opinion, that's not worth a poor performing engine at the risk of damaging engine.
Good luck!