Pontiac Repair: sunbird charging gauge problem, torque converter clutch, advance auto parts

Question
Hi. My 92 sunbird (3.1L) has been running a bit rough when the brake is applied in drive. The engine will run fine, then begin to run rough and the charging gauge will dive down for a second and then return to normal. Sometimes the lights will dim also. Lately, the charging gauge will drop down about 25% and stay there until I accelerate, and sometimes it will overcharge. It is not the Torque converter clutch as it was replaced last year and is not the same kind of problem (will not stall). Any ideas?

Answer
Hi George:

First off has the battery gone dead recently in this car? If so then the engine computer has lost it's "idle memory" there is an idle learn procedure that this car need so it doesn't have an erratic idle. If the battery has not gone dead then you could have a dirty or slow responding idle control motor or a dirty throttle plate. The other way to look at it is that is the charging system voltage drops low enough the igntion system and fuel pump are affected by the low voltage. As for that I would #1 check the battery cables to be clean and tight and also the ground cable on the engine is tight and clean. Then I would have the battery and alternator tested. places like auto zone,Advance auto parts do this for free. You may have an alternator that is going bad and the battery is weak and can't make up for the lack of charging that the alternator is doing. As far as overcharging that's not good for the battery either. Good luck and happy holidays :)