I have quite a big problem. I have a nice 95 WRX Turbo, but the engine has played up. The car was running fine and no power loss or problems were noticed. The car was stopped and when i came to try to restart it it would only fire on two cylinders. I changed the ecu and this had made no difference. I have found that if i disconnect the regulator on the alternator that i can get it to run on three cylinders. I had the alternator checked out and its fine to.
It has become quite baffling and a hassle, it must be an electrical fault but im unsure where to start looking.
Thanks

 

check your gaskets to see if they are leaking, subarus are natorious for head gasket leaks, that or get a new engine lol

 

Surefire

First off you need to see if your having an Ignition, Fuel delivery, or compression problem. you might have a simple basic tuneup problem. Don't get to scared right off the bat.

Get a spark tester, check ALL 4 plugs for spark.
Check your fuel pressure
Check your engine Cranking compression.

These are the first simple test taht will give you a direction to go for repairs or further diagnosis.

Nick