2004 Mitsubishi Galant - rough idle


#1

My Galant has 49k miles and recently started to idle a bit rough. A few months back I installed a K&N airfilter.

Sometime when I come to a stop the car really idles down and then smooths out a bit, somtimes it idles down to a point I feel it might stall, it has never stalled. Did installing the K&N airfilter do something to my car?

Any ideas on what might be causing the car to idle down so much at stops, anything I can do to fix the problem.


#2
I can think of two things. 

It may be a good time to change the plugs and wires if they are original.  Get the same OEM products.   

 Take it in to Autozone or Advanced Auto Parts or another provider and see if there are any stored error codes.  I suspect you will find a problem with the air sensor as those K&N filters have a bad habit of killing them.  The cause is the fact that oiling them properly is kind of tricky and many owners don't do it properly and they end up paying big bucks to repair the damage it causes.  You are likely far better off with OEM filters.  Unless you engine has been greatly modified, it is unlikely you are gaining anything from that filter.

#3

clean the mass air flow sensor and throttle body and car will run great again.