Quirky problems with a 2000 Chevy Lumina

Hi Folks, Any Chevy electrical experts? I bought this Lumina last Monday as a replacement for the Escort favorite son rolled over. Real nice running car MOST of the time anyway. Every so often the engine will be hard starting and run rough. I have a new fuel filter to put on this morning. When I moved the car to the garage it started hard and ran rough. Now for the quirks. The doors locked seemingly for no reason and the headlights flashed almost like something lost contact for a second. This is leading me to believe maybe there's a ground problem somewhere. I've taken the ground cable off at the engine and cleaned the battery ground cable end and the smaller wire end at the engine connection, this wire goes into the harness and presumably into the passenger compartment. I also cleaned the ends at the battery AND the wire off the negative terminal that is lugged to the core support. also cleaned the ground wire ends on the core support that I assume go the the front lights.
NOW my big question, are there other pertinant grounds that arn't readily apparent? ie: at the ECM or BCM (where the heck are these in this car?) I figure I'm going to take care of the simple things like filters and making sure things are clean and tight before I get to crazy with repairs. This car is in really decent shape especially for a car from New York State (no offense New York guys but your emissions standards are chasing nice cars south)!
Thanks for your help.

I would definitely look for a ground near the ecu in the passenger compartment. Does this car have a electrical logic board under the fusepanel in the engine compartment?

Aaron

Aaron, Where in the passenger compartment is the ECU? I haven't had to deal with the electronics in a Lumina yet and don't have a book. I've been dealing with Escorts and F-150s for the past year and a half.
Thanks.

I have seen these kinds of things triggered by bad connectors at the end of the wiring looms.

Had a friend take his Lumina to a dealer that insisted that the computer was bad. He shelled out the replacement cost and still had the same issue. Dealer finally discovered that the car smoothed out when they wiggled the connector to the computer. He got his money back.

My daughter had a '96 Grand Prix that had wierd lighting issues. Bad connector at the main lighting switch. I had a 2000 Taurus with a frequent air bag warning light. You guessed it, bad seat sensor connector under driver's seat. Same Taurus went through 3 EGR position sensors in the 120K miles that I put on it.

Any fault codes being triggered?

That's what I'm leaning toward. I'm thinking there's a marginal ground or connector somewhere. I guess I'm hoping someone will chime it and say "seen dozens of these with the same problem, just clean this connector or ground" and life will be good! Hey I can hope can't I?

Steve;
Pull the taillights and check for water damage there while you're at it. Those were bad year's for Chevy's in the elecrtical department.

Believe the computer is under the hood on the Lumina.

I'll have to look around. Why wouldn't it be, looks like they crammed every component of the car under the hood. Found this out 3 years ago when I replaced the battery in favorite daughter's 97' Lumina!