Check the cables from the battery to the starter motor for clean and tightness, all the way. The battery point under the bonnet may be corroded or/and loose too.
If you are really certain the battery is good (test it with an inductance tester or time how long it takes to run down from fully charged to dim with just a 55 Watt headlamp bulb connected across it, 20 hours is average for a 100 Amp-Hour battery) then the cables and starter motor are next suspects. Starter motors can do this, for a few months before they fail completely, I've had this on another car, long ago, and also listened to another Toyota Prado which my mechie was looking into which did that last month. The owner said that it had been doing it for about a year, sometimes slow cranking, sometimes as good as gold. But it didn't sound like my Prado, which always whirs into life. It sounded tired and softer.
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If you are really certain the battery is good (test it with an inductance tester or time how long it takes to run down from fully charged to dim with just a 55 Watt headlamp bulb connected across it, 20 hours is average for a 100 Amp-Hour battery) then the cables and starter motor are next suspects. Starter motors can do this, for a few months before they fail completely, I've had this on another car, long ago, and also listened to another Toyota Prado which my mechie was looking into which did that last month. The owner said that it had been doing it for about a year, sometimes slow cranking, sometimes as good as gold. But it didn't sound like my Prado, which always whirs into life. It sounded tired and softer.
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