Mitsubishi Repair: 96 Eclipse Stalling, mass air sensor, air fuel ratio

Question
We have a 1996 eclipse, manual, which has over 100000 miles on it. Just recently, the car starting stalling when stopping, slowing down, or taking a turn in first gear.  Then it started doing it in all gears.  It will sound like it's backfiring (like it's exploding!) and then stall.  This started happening after we got the turbo installed.  Do you think that the turbo has anything to do with it?  My boyfriend said that it's the wiring harness, the part that goes into the engine, and that the part will cost $1000 to fix, and to replace the whole wiring harness will be close to $2000!  We do not have that kind of money, so what do you suggest?  Thanks.

Answer
Tantan,
It's possible your boyfriend may have knocked a few electrical connections loose while installing your turbo, but odds are that you'd be seeing problems all the time; not just at idle speeds.

Stalling while turning could indicate an overly tightened power steering pump belt.  Typically when the turbo is replaced, the power steering pump needs to be moved out of the way for easier access to the turbo.  If that belt was overtightened, that will put excess load on the engine; causing a stall.

Your problem may also be caused by a lack of air and/or fuel.  With a new turbo installed, your fuel pump will need to work harder to keep up with the larger amounts of air entering your engine.  If the air/fuel ratio is incorrect, your car most definitely will stall.  If way too much air enters, and not enough fuel, you may experience detenation.  That is basically a premature igition of all the super heated air and little fuel before it is supposed to ignite.  That will force your piston down at the incorrect time, which can eventually destroy internal engine components.  Definitely not good.  Have your fuel pump checked, and replace your fuel filter if it's over 2 years old.

Also, have your Mass Air Sensor checked.  Check your air filter and all intake hoses too.  A worn intake manifold gasket can also cause this problem.  Any unmeasured air entering your engine can cause stubbling and stalling.  A clogged PCV valve can cause similar problems.  Replace that as well.

Other items like your Idle Air Control motor, EGR valve, Throttle Position Sensor and Fast Air Valve should all be checked.  If your boyfriend was able to replace your turbo, he should understand what these items are, and should be able to check them out for you.  Don't go running out to buy that $1000 or $2000 just yet!
Good luck!