Toyota 1AZ: Everything You Need To Know

In 2000, the iconic Toyota 3s engine was replaced by its successor, the 2.0 Liter 1AZ, and confidently came into the automotive market.

These AZ series came out knocking into the industry to replace the Toyota S series engines in 2000. Its predecessor, the 3S-FE, has been ruled to halt production since the emergence of the 1AZs. 1AZ engine includes many technologically advanced methods at that particular era, such as introducing the electronic throttle control, revised valve timing, and the adoption of planar type sensors for measuring air-fuel ratio integrated with the oxygen and flat type knock sensor.

The Toyota 1AZ-FE also features a lightweight Aluminum block with thin cast-iron cylinders and cylinder heads that are made of Aluminum with two camshafts (DOHC) and four valves per cylinder (two for both intake and exhaust). The 1AZ-FE engine is integrated with the VVT-i (Variable Valve Timing with intelligence) for the intake side, Toyota DIS (Direct Ignition System) with ignition coil on each spark plug Sequential MPFI fuel injection system. The 1AZ-FE engine is also integrated with the Electronic Spark Advance system (ESA), which selects the timing that is following optimal inputs from sensors.

So today, we will talk about the 1AZ engines. Its engine design, power, aftermarket support, issues, and its overall impact on the automotive industry and community.

Engine Specifications and Design:

  • Production Run: 2000 – Present
  • Cylinder Head Material: Aluminum
  • Cylinder Block Material: Aluminum
  • Configuration: Straight-4
  • Bore: 86 mm
  • Stroke: 86 mm
  • Valvetrain: DOHC 4 Valves Per Cylinder
  • Displacement: 2.0 L (1998 cc)
  • Compression Ratio: 9.6 (1AZ-FE) and 11.0 (1AZ-FSE)
  • Weight: 290 lbs.
  • Max HP: 152 HP at 6,000 RPM
  • Max Torque: 148 lb-ft at 4,000 RPM

Toyota 1AZ is a naturally aspirated, straight-four, 2.0 L gasoline engine. It has two variants, the most commonly known basic 1AZ-FE, and direct-injection integrated 1AZ-FSE. This engine produces 145 HP at 6,000 RPM with 140 lb-ft of torque at 4,000 RPM. In addition, other power output ratings were released for Toyota Rav4 and Ipsum machines at 150 HP at 6,000 RPM and 142 lb-ft of torque at 4,000 RPM. It has a 9.6 compression ratio.

At first, Toyota used a cast-iron material for their cylinder block; however, it was denied for some reason and replaced with a lighter aluminum material with cast-iron sleeves. In addition, the axle of the cylinder was displaced against the crankshaft axis to allow the sleeves to breathe and to weakens the tension on that area.

The 1AZ-FE cylinder block is made of die-cast Aluminum with cast-iron liners, a stamped oil pan, and a die-cast Aluminum lower crankcase; it also incorporates an offset in the cylinder and crank centers. Its spiny-type cast-iron liners are externally cast to form a large and uneven surface. These exterior casts are designed for a better connection, adhesion between the cylinder block and the liners.

This engine has a capacity of 1998 cc with 86.0 mm bore and 86.0 mm stroke. The cylinder block also has water jacket spacers which subdues the water flow on the center of the jacket and guides the coolant flow around the bores. That results in a reduction in backpressure from the bottom of the pistons and a better airflow due to additional air passage holes in the crankshaft bearing area of the cylinder block. And it was integrated with air-conditioning compressor and oil filter brackets into the crankcase.

The crankshaft is made of strong forged steel supported and fully balanced with five journals, roll-finished pin and journal fillets, and eight balance weights. The crankshaft has an offset of 10 mm to the thrust side of the cylinder bore centerline to reduce the effect of friction and fuel consumption by as much as three percent, and there is a gear-driven by two balancing shafts in the lower Aluminum crankcase, between the first and second bearings. These balancing shafts are game-changers vital in reducing engine vibrations; these helical gears are made from polymeric material for noise reduction.

1AZ-FE connecting rods and caps are made from high-strength steel, and Toyota used a nut-less type plastic region tightening bolts for an added weight reduction. It has Aluminum alloy pistons with two compressions and a single oil ring, with heads formed with a taper squish shape. And to reduce friction losses, the piston skirt is coated with resin.

The cylinder head of the 1AZ-FE engine is made of light Aluminum, which is mounted to a steel-laminate type head gasket; Toyota used a shim about the cylinder bore to gain a better surface for sealing. It has double overhead camshafts and acts on four valves per cylinder through bucket tappets. These camshafts are driven by a single-stage roller chain, five bearings for the support, and are lubricated by an oil jet. The chain tensioner used a ratchet type non-return mechanism; and used a spring and oil pressure to regulate the chain’s tension, so it does not break loose that much.

Though it is not commonly mentioned, 1AZ-FE also supplies fuel to the chambers via fuel injection but not D-4S. It uses an electronically controlled sequential fuel injection through a 12-hole injector nozzle, which is located on the inlet ports to avoid wall wetting and fuel bond within the walls of the port. It is also integrated with two air-fuel ratio sensors on the exhaust side for a better response if you are running in a stoichiometric air-fuel mix. To add to that, hot-wire L-type airflow meters are used to measure the intake volume. This engine also has slanted squish pentroof-type combustion chambers designed to improve thermal efficiency and lower the margin of engine knock.

Applications of 1AZ-FE engine:

  • 2002 – 2006 Toyota Camry (Asia Version)
  • 2006 – 2009 Toyota Camry (Aurion Version)
  • 2000 – 2003 Toyota RAV4
  • 2003 – 2006 Toyota RAV4 Euro
  • 2001 – 2009 Toyota Ipsum

1AZ-FSE

1AZ-FSE is the revised version of the 1AZ-FE engine and holds a resemblance to the said engine. However, it is equipped with Toyota’s D-4 direct injection system, deviating from the L-type sequential of the 1AZ-FE. It also applies the same concepts in other parts, such as the electronic throttle body. This version produces 147 HP at 5,700 RPM with 145 lb-ft of torque at 4,000 RPM.

Applications of 1AZ-FSE engine:

  • Toyota Avensis
  • Toyota Avensis Verso
  • Toyota Noah/Voxy
  • Toyota RAV4
  • Toyota Gaia
  • Toyota Isis
  • Toyota Ipsum
  • Toyota Caldina
  • Toyota Wish
  • Toyota Allion
  • Toyota Premio
  • Toyota Opa

Engine Tuning, Modifications, and Upgrades:

If you want to add additional power output to your 1AZ engine, there are supercharger kits available in the market specially designed to fit the AZ engine. You need to buy that kit and bolt it in on your stock internals. But before bolting your supercharger kit, be sure to remove the catalytic converter or but a cat-back exhaust system. Use a Greddy e-manage ultimate to set it up, and you will at least 200 horsepower as a result. It is not recommended to take it further because it would be more practical to buy 1JZ or 2JZ engines, for that matter.

Problems Surrounding 1AZ Engines:

Like standard engines, 1AZ is not immune to any issues and problems. And if you are looking for one of the best ways to take care of your engine, know the problems one or two steps ahead—this not an A-list of issues but a heads-up precautionary measure to avoid further engine damage.

First, is the cylinder head bolts threads wearing out. This issue is the main problem for most AZ engines and prevalent in those cylinder blocks produced until 2007. However, this issue can lead to a worse result by having leaks in your engine, and coolant will also leak through the bolt in-between crevices due to improper clamping to worn-out threads. Also, some common signs to watch out for are engine overheating, coolant residues on the cylinder block back wall, and loss of the cylinder block shape.

Next is the engine vibration on idle RPM at around 500-600 RPM, which is typical for the 1AZ engine. This issue is on for some challenge because you need to clean the throttle body, idle control valve, fuel injectors and thoroughly inspect all the engine mounts. After some of your fixes, there will be a noticeable decrease in vibration, but still, there are not gone completely.

1AZ engines are vulnerable to soot formation that leads to acceleration jerks. You need to clean the throttle body and remove the soot from the intake manifold; it can lower the effects. However, if there are still problems occurring, try to inspect the oxygen sensor and the VVTi.

To add to that, Japanese models are installed with an EGR system (Exhaust Gas Recirculation) that is associated with the soot formation; that results in power decrease and unsteady idle run. If that happens, clean the EGR valve or block it totally.

1AZs are not using hydraulic lifters, so you need to adjust the valves when necessary. Also, the 1AZ-FSE engine is sensitive to fuel quality; if you use low-quality gasoline, your injectors and high-pressure fuel pump will be disarranged, and fixing them is pretty expensive.

Summary

In comparison to its predecessor, the S series, the 1AZ engines reign supreme to its competition due to their higher efficiency, fuel economy, lightweight and compact design, and low noise and vibrations. It has outstanding reliability more-so it can last up to 200,000 miles with the proper maintenance and care. Overall, 1AZ engines are generally good and won’t give you much trouble. Though it has some issues and problems that are detrimental if not solved immediately, these issues are primarily due to external factors and not on the engine design.

I hope that this simple guide helped you understand the 1AZ engines more. The Toyota 1AZ engine’s reliability, issues, potential upgrades, power, application, and community acceptance. This will give you a rundown and an idea of the said engine.

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