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Gen 3 Prius rough cold start plus slow coolant loss

FlatSixTech31Community StarterNov 12, 20252013 Toyota Prius ThreeAtlanta
Older Prius has developed a rough shake for a few seconds on some cold starts and the coolant level seems to be dropping slowly. I don't want to assume the worst. What test sequence would separate ignition, EGR/intake issues and an internal coolant leak? I'm in Atlanta. I'd rather test this logically than start replacing parts.
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4 replies

GarageDriverCommunity StarterCommunity StarterNov 12, 2025permalink
Start with the test that can prove you wrong. Swap the cheap/easy piece first on the 2013 Toyota Prius and see if the fault moves. Save the big job until that test fails. Time, temperature, and whether it's in gear are the notes that actually help a shop. Checking again after work.
WrenchWrenchCommunity StarterCommunity StarterNov 12, 2025permalink
If it were in my driveway, move a coil or plug on the 2013 Toyota Prius if it's cylinder-specific and see whether the code follows. That's the branch I'd chase this week. Post the numbers (or the code) and people can get more specific. Video is ugly but it shows the hesitation.
CleanNomad75Community StarterCommunity StarterNov 13, 2025permalink
This is usually cheaper to test than to guess. Capture voltage while the 2013 Toyota Prius is actually failing — after it restarts you've lost the clue. Save the big job until that test fails. Learned this the expensive way on a previous car. Not interested in a five-hour wait for a shrug.
FlatSixTech31Community StarterCommunity StarterNov 13, 2025permalink
Checked the easy stuff on the 2013 Toyota Prius and found one clue worth chasing before I book a shop. This is the version I'd tell a friend.
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