Q: '00 Buick Century Custom. V6 3100. I am at a loss...

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to start off, the car died while idling 2 different times. The 1st time I didnt notice right away so the battery drained almost completely. The 2d time I caught it right away nd it started back up immediately but the last time I drove it it almost died when I slowed down 2 round a corner but "came back 2 life" when I gave it gas nd I made it the rest of the way 2 work(another 2 blocks). Omw home from work it overheated (thermostat) so I pulled over nd shut it off. When I tried 2 start it again it acted like the battery wasn't charged enough. hasn't been driven since. If I fully charge the battery nd leave the car sit 4 a few days it'll go dead. My 1st thought was alternator but it doesn't drain while driving or running. i replaced the thermostat, plugs, wires, air filter, fuel filter, and changed the oil last night. going 2 check all fuses/relays and recharge the battery and get it tested today and see what happens from there. if the issue is not fixed what should be my next step?
My car has an automatic transmission.

Prior to performing diagnostics be sure you have a fully, 100% charged battery that passes a load test. Then, confirm that the engine immobilizer system (security system) is not activated thus preventing the car from starting. If the immobilizer system is on, you may see a security warning light. To temporarily override the immobilizer system, see these instructions. You mention that the battery died after just 4 days with the car off. If that battery happened to pass the load test, use an ammeter to rule out any parasitic (excess) load on the car’s electrical circuits that might be causing the battery to discharge even when the car is off. If the battery did NOT pass a load test, you can omit this step. Anytime, there is excess current flow that is slowly draining the battery, a Mechanic would use an ammeter to test all of the various circuits until the faulty circuit with the excess load (current draw) is found. Obviously, if the battery discharged "on its own", because it is bad, you need not look for excess loads.


If the battery tests good, and there are no parasitic loads, attempt to start the car. Basically, if a fully charged battery is powering a starter motor that is turning the engine over RAPIDLY, at sufficient RPM, but the engine does not catch and run, that means that there is an ignition, fuel, air induction, or mechanical fault in the engine that will have to be repaired. Be sure there is adequate fuel in the fuel tank and that the fuel is not old. Check for adequate fuel pressure (does the in tank fuel pump whirr momentarily at the instant you turn the key to the "on" position?; if not, you have a dead fuel pump), injector operation, and a spark at the spark plugs. In your circumstance, with a fully charged battery, if the starter is NOT performing well (turning at adequate RPM), then you may need a new starter motor. There are many causes of hard starting, and stalling once started, but illustrative ones are a faulty engine coolant temperature switch (sensor), worn spark plugs, inadequate fuel delivery or pressure (clogged fuel filter), and contaminated or old gasoline. If you get the engine started, but it stalls, there could be a problem with the throttle position sensor, the idle air control valve, the EGR system, vacuum leaks, and so forth. Whether the vehicle does not start, starts and dies, or stalls, if you simply request a no/hard starting - engine diagnostic the responding certified mechanic will get this resolved for you promptly. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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