Q: 1999 Mitsubishi Eclipse running rich and stalling at idle

First of all, you’ve got to realize that, although those technically don’t have a MAF mass air flow sensor, those use what is called a Karman vortex sensor. Those sensors are notorious for going bad on Mitsubishis.

They do the same thing--they measure how much air is going into the engine to tell the computer how much fuel is going to put into a fuel injector. You will want a certified technician, such as one from YourMechanic, to come and hook up a high-level scan tool and analyze the Karman vortex sensor.

That can easily be what the problem is. If it is not that, running rich either means that you are getting way too much fuel, or you are not getting enough air. So, you’d want to check and see if you have any air restriction on the intake.

Something as pesky as an air clogged air filter can do that. You can also have a problem with the fuel filter. You might check it, to see if the fuel filter is clogged or anything like that. But, your throttle position sensor is reading 13% at idle. That is actually a little bit high. If it’s saying that it’s a little more open than it is, then the computer will send more fuel to the car and that will make it run rich. That a lot of times can cause that problem too. That’s a relatively common thing that happens to those cars. I recommend getting the car checked and having a qualified technician diagnose your stalling issue. That way, you can be more certain about what repair is needed.