Prius sometimes has rumbling sounds under the hood when first turned on which seems to last for a few minutes until the car warms up. Orange Engine light comes on and stays on until reset. Plugs were replaced. Gas treatment might help for a little while but does not last. Our great independent mechanic is stumped. Help!!!
you need to post the codes from the check engine light to start get some help here. if you do not know the codes, most Autopart’s stores will scan your vehicle for free and then you can post them. the more info you give the more we can help.
The head gasket is leaking. These engines are known for coolant leaking into the cylinder after shut-off while the cooling system is under pressure. Then on start-up that cylinder misfires causing the shake and camshaft gear noise.
While the cooling system is under pressure, remove the spark plugs and inspect the cylinders for drops of coolant.
Other examples of this at Car Complaints;