The 1MZ-FE is a naturally aspirated 3.0-liter V6 with a lightweight alloy block and head and dual overhead cams connected to 24 valves with VVT-i variable valve timing. It also features a cast-aluminum intake manifold together with multipoint fuel injection. It is generally considered to be a robust engine, but it can struggle with oil consumption, oil sludge, an untrustworthy knock sensor, VVT-i problems, and EGR failure.
The oil-sludge problem is a result of an aging engine that develops oil leaks and is considered to be the most common problem for this engine. It even resulted in a class-action lawsuit from several consumers as it is believed to have affected almost five million Toyota products. This was settled by the brand in 2007 when it agreed to execute repairs on all cars for up to eight years. If your unit wasn't covered by this, you'll notice sludge build-up if the second bank's spark plugs are coated with excess carbon. You may also notice a gray shade of smoke being emitted from the exhaust system when you start the car. Lastly, there will also be oil on the floor of where the car is parked. Some less common problems you may also experience include faulty camshaft caps, excessive oil consumption, and valve stem leaks. To resolve the oil-sludge problem, you will have to address the oil loss and replace any seals or gaskets that are showing signs of progressive wear.
The 1MZ-FE is fitted with a knock sensor which can be a bit problematic. This sensor is tasked with detecting vibrations from the engine caused by pre-ignition or knock and will reduce the car's power if it notices pre-ignition, but it can go awry. You'll notice bad fuel economy with the failure of this part. Once the sensor starts failing, it'll cut power for any irregular vibration, even if it is not related to a pre-ignition condition. Once this starts to happen, you will have to get it replaced altogether.
The 1MZ-FE's EGR failure is due to wear and tear, particularly with the EGR valve. Once this system starts to give in, you will notice an increase in fuel consumption, a rough engine idle, and engine stalling problems with the Toyota Camry. You may also notice a strong smell of gasoline from outside of the car as well as knocking noises. To resolve this, you will have to get the valve replaced. EGR fault codes include P0400, P0401, P0420, P0430, P0440, P0441, P0442, P0443, P0446, P0453, P0455, P0456, P1410, and P1411.
The last common problem with the Toyota Camry's 1MZ-FE is the VVT-i variable valve timing, which is affected by wear and tear. This will lead to a rough idling engine, a struggle to maintain speed, and an illuminated Check Engine light. The Toyota Camry can also experience acceleration problems. The P1656 and P1346 fault codes indicate that the VVT system is at fault. If this occurs, you will need to have the system serviced.
Something that you should be aware of is that the 1MZ's camshafts run on a timing belt which needs to be replaced every 90,000 miles as per Toyota's recommendations. It is essential that this is done because failure to change the belt can lead to catastrophic mechanical problems with the Toyota Camry. If you notice ticking or slapping engine sounds, an illuminated Check Engine light, and a loss of power, your timing belt is likely starting to fail. You may also notice engine misfiring, which will bring up the P0300, P0301, P0302, P0303, P0304, or P0305 fault codes with the last number signifying which bank is at fault. Never wait this long and replace the timing belt when it is due, because it may also fail without any warning at all. The V6's water pump also runs on the timing belt, so it is advised that you replace this part as well during this service because the seizure of the pump can also snap the belt.
Mileage: Oil sludge and oil consumption can start from 80,000 miles. Knock sensor failure does not have a mileage attached to it. EGR-related problems tend to take place in around the 120,000-mile area. VVT-i component problems appear to start from 100,000 miles.
Cost: New gaskets and seals for the 1MZ-FE range from $5 to $60 while the cost of labor is dependent on which part needs to be replaced. Having the knock sensor replaced is fairly affordable as parts and labor should cost only around $300. A new EGR valve should not cost more than $400 for parts and labor. The VVT-i service may be a bit costly, with an estimated quote of around $1,000. A timing belt and water pump service should cost close to $1,000.
How to spot: Oil consumption-related problems will lead to sludge build-up, fouled and worn spark plugs, a smoky exhaust, camshaft-cap issues, and oil puddles under the car. A bad knock sensor will lead to a loss of power, hesitant acceleration, and bad mpg. EGR problems are indicated by a rough idling engine and spontaneous stalling, an increase in fuel consumption, gasoline smells, and knocking noises from the engine bay. VVT-i problems are announced by a rough engine and an illuminated Check Engine light.