Toyota 1AZ-FE Engine Specs And Problems

AZ series was introduced in 2000 – to gradually supplant the legendary S series, and for ten years, remained the main mid-size engine of the company. They were installed in many initially FF C/D/E-class cars, vans, and light- and medium-SUVs.

The 1AZ-FE engine can be seen as a simplified version of 2AZ-FE.

• There is no balancing mechanism.
• No oil nozzles in the block.
• Pistons have a larger skirts.

– For some regions, specific modifications were produced – for leaded gasoline, without VVT, without the converter, and relative components.

1 AZ Engine Specs

What Cars Have The Toyota 1 AZ Engine?

• 2006–2009 Toyota Camry (Aurion version)
• 2001–2003 Toyota RAV4
• 2003-2006 Toyota RAV4 Euro
• 2001–2009 Toyota Ipsum
• 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

1AZ-FE Engine Problems

Inside the block cylinder, you’ll find a few strips of metal. The major issue with all AZs is that they don’t all perform at the same level. Some of the most typical symptoms of an issue are coolant on the cylinder block back wall and an engine overheating. You may also be deformed. Finally, you’ll have to replace the cylinder block.

At idle, there is engine vibration. You can feel it when engine RPMs fall to around 500-600 rpm. This is typical of an engine, and stopping the condition may be difficult. To reduce vibrations, clean the idle control valve, throttle body, and fuel injectors, and check all of your engine mounts.

It’s a bit difficult to drive – because it has no power assist. -> It’s hard to accelerate since there is no power assist. Remove soot from the throttle body and intake manifold. That should assist. The 1AZ is prone to soot formation. If any faults remain, inspect the VVTi and oxygen sensor.

1AZ-FSE (2.0 D-4) And 2AZ-FSE (2.4 D-4)

1AZ-FSE, 2AZ-FSE – transverse, with direct injection, for initially FF cars, vans, and SUVs. Installed in: Allion/Premio 240, Avensis 220..250, Caldina 240, Gaia, Isis, Nadia, Noah/Voxy 60, Opa, RAV4 20, Vista 50, Wish 10.
By 2009 replaced by ZR engines with traditional multipoint injection (and Valvematic system).

There are some differences in the mechanical part of D-4 engines.

• The higher the compression ratio.
• The fuel injectors are mounted in the cylinder head.

• A high-pressure fuel pump is driven by an additional cam on the inlet camshaft.
• Variable valve timing range 43°.

– The pistons have a specific shape which helps to lead the fuel spray to the area of the spark plug. The top ring groove has an anti-wear alumite coating.

– Some models were equipped with an oil cooler.

1AZ specs– Differences of version for Japanese domestic market (type’2004): a compression ratio 10.5 instead of 9.8, three-layer cylinder head gasket instead of a two-layer, another shape of the combustion chamber, additional channels for coolant between the cylinders, the other valve timing, intake valve lift 9.4 instead of 8.2 mm, exhaust – 8.0 instead of 8.6 mm, reduced by 1.1 mm piston height.

ETCS (Electronic Throttle Control)

Driven by motor with control unit commands. When starting the throttle is slightly opened to allow additional air intake, and then the opening angle decreases depending on the coolant temperature. At the homogeneous mode idling speed is adjusted by throttle moving, at LeanBurn mode – by fuel supply volume correction with constant throttle opening. In addition, ETCS performs traction control (TRC) functions and some stabilization system (VSC) functions.

Driven by motor with control unit commands. When starting the throttle is slightly opened to allow additional air intake, and then the opening angle decreases depending on the coolant temperature. At the homogeneous mode idling speed is adjusted by throttle moving, at LeanBurn mode – by fuel supply volume correction with constant throttle opening. In addition, ETCS performs traction control (TRC) functions and some stabilization system (VSC) functions.

SCV (swirl control valve) actuator. There is an SCV block between the cylinder head and the inlet manifold, which closes one of two inlets channel to each cylinder, depending on the driving conditions. A vacuum actuator drives the flaps.

– At low speed, low load, low coolant temperature, SCV is closed, and air flows through one port, which increases flow speed and forms a vortex in the cylinder, for better mixture turbulization.
– At a high load, SCV opens and air flows through both ports.

Considering the air supply system features, an additional pressure sensor for the brake servo was implemented to switch the mode that provides the specified vacuum level.

EGR System (Domestic Market)

The exhaust gas recirculation system of D-4 engines provides an inlet of a significant proportion of the exhaust gas at LeanBurn mode (much more than in traditional engines). It allows for low combustion temperature, decreases the content of nitrogen oxides in the exhaust gases, and reduces pumping losses at the inlet.

EGR valve is driven by DC step-motor. The opening angle depends on the engine speed, coolant temperature, load, and vehicle speed.

Exhaust gases from the valve flow into the EGR aluminum manifold, which uniforms a stream of gases in each cylinder. Both the valve and manifold are water-cooled.

NOx-converter (Domestic Market)

In the exhaust pipe of the Japanese models, a NOx converter is installed. LeanBurn mode is accompanied by increased emission of NOx when the nitric oxide reacts with oxygen of the exhaust gas (O₂), and products are accumulated on the catalyst adsorbing material in the form of nitrates (NO₂).

Inhomogeneous mode, with a sufficiently rich mixture, the content of CO and HC in the exhaust gases increases, with its involvement in the presence of platinum dioxide (NO₂) is reduced to nitrogen (N₂). Simultaneously the accumulation of nitrogen oxides converter actively captures the sulfur, which takes the useful volume of the absorbent layer, so the system can to function normally only using low-sulfur gasoline.

Ignition system – DIS-4, spark plugs with iridium center electrode (initially for overseas market – Denso SK20R11 / NGK IFR6A11, since MY2003 – Denso SK20BR11 with two additional side electrodes, for the domestic market – SK20BGR11 – protruded in the combustion chamber due to long shroud).

Type’2004 differences: L-type control system with MAF sensor, ETCS actuator with a throttle position sensor (Hall effect), absence of separate NO-converter.

Owner’s Experience

In addition, several specific points are added:

1. The tendency to noticeable vibrations due to low nominal idle speed drawdown further with minimum deviations of engine management system components operation. Sometimes the traction loss at medium speed occurs, and driving performance deteriorates. Often, the cause can not be found even by whole unit replacement. In some cases, cleaning of MAF sensor, throttle, and SCV actuator and replacing the VVT valve, ignition coil terminals, and EGR forced clogging may be useful. To partially smooth discomfort from rpm subsidence helps the replacement of the engine mounts (primarily – liquid filled).
2. Direct injection and control system has no such critical defects as first-generation (3S-FSE), and require less attention. Recommended to be extremely careful with brittle plastic parts of the injectors (~$300). Sometimes injectors are required in case of coil deteriorates. Replacement of low-pressure electric pump and fuel tank filter often requires. Note formal recall campaigns concerning fuel pipe replacement and the fuel pump check valve for the Avensis 250.
3. EGR operation traditionally causes a strong carbon deposit in the inlet – from the throttle to the SCV and valves, and therefore requires regular mechanical and chemical treatment. Otherwise, problems of rpm drawdown and cold start are inevitable. There is no EGR at -FSE engines for the domestic market, but it does not eliminate the need for cleaning the intake of the oil sludge.

Summary

After more than ten years since the first AZ appearance, we can evaluate the series as a whole.

Specs. Power output and torque – are consistent with the average level of Asian analogs and in most cases provide enough thrust-weight ratio (except perhaps medium-SUVs).

Direct injection. D-4 did not cause significant performance gain or improvement in fuel efficiency compared to conventional motors of AZ series and performs primarily “environmental” objectives. But the increased maintenance and repair cost of the “excess” components is enough to make once again sure of the worthlessness and harm of using direct injection engines on the low-forced natural aspirated engines. Although 1..2AZ-FSE are more reliable than a terrible 3S-FSE, ordinary 1..2AZ-FE with multipoint injection are less of a problem.

Not to mention that because of an incurable idling low rpm problem (with the attendant vibrations), such cars driving is uncomfortable. Small note – in 2008 the known Asian auto-repairer wrote: “but the progress is not standing still, and MFI soon be will be replaced by DI,” but in reality, the D-4 history has developed somewhat differently.

Repairability. From the manufacturer’s point of view, AZ is considered “disposable”, as well as all the modern engines without an “oversize” concept. Of course, in despair, these engines are subjected to overhaul, with cylinder block liners replaced using non-original parts or matched counterparts from other brands. The minimum cost of such work, as usual, is comparable to the price of the used engine – $1500-2000, whereas in the top workshops, a complete overhaul is valued at $4000-5000. As with other aspects of maintainability, here things are good – 2AZ-FE and 1AZ-FSE and shipped both to the European and the domestic markets, which has removed a lot of problems with spare parts and “second hand” engines.

Reliability. In the aggregate of most specs, the AZ series could be considered not bad representatives of the “3rd wave” motors. Still, only one critical defect of the cylinder heads ever eliminated their reputation, becoming a congenital malformation of popular models (Camry 30, RAV4 20, Highlander 20…), and undermining confidence to even later modifications.