QuestionHello, i'll get right to it. I have a 1994 Mitsubishi 3000GT, Base,3L V6 24V N/A DOHC, Auto. It started after I changed my alternator. As soon as i cranked the car for the first time with the new alternator it started to idle roughly, slightly shake, and i noticed a bit of power loss and poor gas milage. When i put the car in Drive the shaking gets worse. Since then i've tested the compression and it was higher than normal due to carbon deposits. I put the old alternator back on to see if that was the problem, but it didnt help (the new one is back on now). I installed new plugs and wires. That helped a little with the idle and power loss but it still is not the same as it used to be. This may help: the old alternator was 110Amp, the new alternator is 90Amp - i was told that shouldnt be a problem. Fuel filter is new. I did have to remove the timing belt cover but i didnt touch the belt itself. When i changed the alternator i also replaced a valve cover gasket. Could a leak there be causing a problem. Thanks in a advance.
AnswerAlan,
A leaking valve cover can cause a sputtering problem. A common cause is a bad PCV valve that is attached to the valve cover. I'd recommed replacing it. Most auto parts stores sell them for your car, but I'd suggest getting one from the dealership. They are not very expensive (about $5-$8) and they are easily replacable.
Your new 90Amp alternator should not cause this problem. Double check to make sure your ground cable for your alternator is securely connected. Sometimes adding an additional ground wire to a different part of your car's frame can help.
Be sure to check your ignition and fuel injection fuses. The ignition fuse sometimes blows when a new alternator is installed because of the sudden surge of current that passes threw it.
You may want to consider pulling off your intake manifold, throttle body, and EGR valve, and given them all a good cleaning with a carb cleaner.
Good luck!
