Toyota AZ series engine

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Nov 2004 - Nov 2013

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

Engine Displacement, cm3 Bore x Stroke, mm Compression ratio Output, hp Torque, Nm RON Weight, kg EMS Standards Model Year
1AZ-FE 199886.0 x 86.0 9.8147 / 6000192 / 400095 117EFI-LEECAZT2502003
9.8152 / 6000194 / 400095 131EFI-LEECACA302006
9.5137 / 5600190 / 400095 112LGEECAZT2502003
1AZ-FSE 199886.0 x 86.0 9.8152 / 6000200 / 400091 -D-4 JISAZT2402000
10.5155 / 6000192 / 400091 -D-4 JISAZT2402004
11.0147 / 5700196 / 400095 124D-4 EECAZT2502003
11.0149 / 5700200 / 400095 -D-4 EECAZT2202000
2AZ-FE 236288.5 x 96.0 9.6160 / 5600221 / 400091 -EFI-LJISACM212002
9.8170 / 6000224 / 400091 138EFI-L JISANH202008
2AZ-FSE 236288.5 x 96.0 11.0163 / 5800230 / 380095 -D-4JISAZT2502006
2AZ-FXE 236288.5 x 96.0 12.5131 / 5600190 / 400091 -EFI-LJISATH102007
12.5150 / 6000190 / 400091 -EFI-L JISAHR202009
3AZ-FXE 236288.5 x 96.0 12.5150 / 6000187 / 4400- -EFI-LCHNAHV402010

2AZ-FE (2.4 EFI)

2AZ-FE - transverse, with traditional multipoint injection, for initially FF cars, vans and SUVs. Installed in: Alphard 10..20, Avensis Verso 20, Blade 150, Camry 30..40, Corolla/Matrix 140, ES 40, Estima 30/40..50, Harrier 10..30, Highlander 20, Ipsum 20, Kluger, Mark X Zio, Previa 30..50, RAV4 20..30, Rukus 150, Scion TC 10, Solara 20..30, Vanguard 30.
Since early 2010s gradually replaced by ZR and AR series.

- 2AZ-FXE - for FF hybrid cars (Alphard Hybrid 20, Camry Hybrid 40, Estima Hybrid 10..20, HS250h, Previa Hybrid 20, SAI).
- 3AZ-FXE - for hybrid cars (Camry Hybrid 40 CHN).

Cylinder block

The cylinder block - aluminium "open deck" with thin cast iron liners. The liners are fused into block and their special rough outer surface promotes strong connection. Of course, no overhaul with reboring officially provided.

The massive alloy crankcase mounted to block also performs the function of the sump upper part and the stiffener.

Forged steel crankshaft with 5 journals and 8 balance weights is held by individual main bearing caps. The axis of the crankshaft has been shifted by 10 mm relative to the cylinder axis lines ("desaxage"), thus reducing the lateral component of the force exerted by the piston to the cylinder wall, reducing wear.

As usually for Toyota's R4 engines with displacement over two litres, the balancer mechanism is installed with direct drive from the crankshaft (by polymer gears - to reduce noise). But besides the improvement of comfort, it creates another potential weakness of the engine mechanical part.

A - plastic gears

Pistons - aluminium, moderately cut skirt with a friction reducing polymer coating. The pistons are connected to the rods with fully floating pins.

At type'2006 there is the spacer in the water jacket, it allows more intensive coolant circulation near the top of the cylinder, which improves heat dissipation and helps to more evenly thermally load.

Cylinder head

Cylinder head of traditional design, with a close to the vertical direction of the intake port for efficient intake and holes for injectors. Head cover is cast of magnesium alloy.

Timing drive

Timing drive - 16-valve DOHC, driven by single-row roller chain (pitch 8 mm), with hydraulic tensioner (with ratchet mechanism) and lubricated by separate oil nozzle.

There is VVT (variable valve timing system) sprocket on the inlet camshaft, the range - 50° (type'2006 - 40°).

The valve clearance is adjusted by a set of tappets, without adjusting washers or lash adjusters. Therefore, owners prefer to abstain from rather complex and expensive procedure of adjusting.

It is quite difficult to predict the chain life time - rarely no need to replace it up to 300.000 km mileage, but more often stretches to 150.000 km (accompanied by by excessive noise, especially after start, and trouble codes concerning to timing). Together with chain replacement it would be appropriate also replace other components (sprockets, tensioner, guides), as used ones contribute to a rapid wear of a new chain, but as the inlet camshaft sprocket is assembled with VVT actuator (~$120) , so most owners does not follow this recommendation . The hydraulic tensioner requires relatively frequent replacements, but it can be perform easy from the outside, without removing of the chain cover.

Lubrication system

Trochoid type oil pump is installed in the crankcase and is driven by additional chain. On the one hand, it increased the number of moving parts, on the other - the conditions of oil pumping improved.

Oil nozzles that lubricate and cool the pistons are provided.

The oil filter is located vertically under the engine.

Cooling system

The cooling system is classic for the 3rd wave engine: the pump driven by serpentine belt, the mechanical thermostat is "cold" (80-84°C), radiator fans are controlled by ECM via relays (without coolant temperature switch).

1 - thermostat, 2 - water pump, 3 - cylinder block, 4 - cylinder head, 5 - radiator, 6 - heater, 7 - throttle body.

Intake and exhaust

Manifolds location - as at the previous generation of engines - intake at rear, exhaust at front. Notable innovation - a plastic intake manifold (to reduce weight and cost, and reduce heating of the inlet air) - enough unproblematic even for winter conditions.

Some models have the muffler with a mechanical valve that regulates the flow of exhaust gases. At low speed closed valve helps to reduce noise, at high speeds it is opened reducing the back-pressure.

Fuel injection system (EFI)

Fuel injection - traditional multipoint, sequential under normal conditions. In some conditions (low temperature and low speed) paired injection can be performed. In addition, injection can be also performed synchronized (once per cycle at the same position of the crankshaft, with managed time of injection) or unsynchronized (by all injectors simultaneously).

Fuel system - without a return line, with the pressure regulator and the fuel filter built in pump module, the fuel pressure - about 325 kPa. Pulsation damper mounted to aluminum fuel rail. The quick-split type connectors are used for fuel lines.

The injectors with multi-hole nozzle are used to improve dispersion of fuel.

The control system - "L-type SFI", with mass air flow sensor (MAF) "hot wire" type, combined with intake air temperature sensor. RON requirements - 91 / Regular.

1 - air flow sensor / intake air temperature sensor, 2 - absorber 3 - EVAP VSV, 4 - ETCS, 5 - ignition coil, 6 - VVT actuator, 7 - VVT valve, 8 - injector, 9 - knock sensor, 10 - crankshaft position sensor, 11 - camshaft position sensor, 12 - coolant temperature sensor, 13 - oxygen sensor, 14 - ECM, 15 - throttle position sensor, 16 - AFS sensor, 17 - accelerator pedal position sensor.

In 2001-2003 the modification with mechanical throttle drive and classical idle control (by rotary solenoid) produced.

1 - air flow sensor / intake air temperature sensor, 2 - absorber 3 - EVAP VSV, 4 - ISCV, 5 - ignition coil, 6 - VVT actuator, 7 - VVT valve, 8 - injector 9 - knock sensor, 10 - crankshaft position sensor, 11 - camshaft position sensor, 12 - coolant temperature sensor, 13 - oxygen sensor, 14 - ECM, 15 - throttle position sensor, 16 - converter, 17 - resonator.

1 - throttle sector, 2 - ISCV (idle speed regulator), 3 - throttle position sensor, 4 - coolant pipe, 5 - purge pipe.

However, most models are initially was equipped with electronically controlled throttle valve (ETCS): DC motor, dual-channel potentiometer (by MY2003 replaced by contact-less sensor (Hall effect)), with a separate accelerator pedal position sensor (initially potentiometer, since type'2006 - Hall effect). ETCS functions is idle speed control, cruise control and torque control during gear changes.

There are few variants of oxygen sensor installation:

- pair of oxygen sensors (89465) before double converter
- oxygen sensor (89465) before and after converter
- one air-fuel ratio (AFS) sensor (89467) before converter and oxygen sensor (89465) after converter
- pair of AFS sensors (89467) before double converter and pair of oxygen sensors (89465) after

Since type'2006 widely used planar type AFS (advantage - more rapid heating).

1 - expander, 2 - ambient air, 3 - heater.

Crankshaft and camshaft position sensors still was traditional inductive type.

In MY2003 "flat" piezoelectric knock sensor was introduced, unlike the old type of resonant knock sensors it feels a wider range of vibration frequencies.

1 - piezo, 2 - insulator, 3 - steel weight, 4 - resistor, 5 - vibroplate. A - "flat" type, B - resonance type.

At North American market ECM also had to perform control of too complex and capricious fuel vapour recovery system (EVAP).

At type'2006 for some markets with strong emission standards IMRV actuator in the intake was installed, which closes half of intake ports at cold engine idling, thereby creates a strong turbulence and improves the efficiency of the combustion process.


Ignition system - DIS-4 (separate coil with integrated igniter for each cylinder). Spark plugs (Denso SK20R11, NGK IFR6A11) with the iridium central electrode.

1 - primary coil, 2 - secondary coil, 3 - voltage protection circuit, 4 - current protection circuit, 5 - pulse generator, 6 - locking circuit, 7 - amplifier, 8 - control circuit. A - igniter, B - ignition coil.

Starter - with a planetary gear, segment armature winding, interpolation magnets.

Alternator - after MY2003, new generators with a conductor segment. Since MY2006 overrun clutch was installed - with a spring between the inner and outer portions of the pulley which transmits torque only in the direction of rotation of the crankshaft, reducing the load to belt.

1 - crankshaft, 2 - tensioner, 3 - power steering pump, 4 - alternator, 5 - water pump, 6 - compressor.

Auxiliary drive - by serpentine belt with automatic spring tensioner. The advantage - compact size, the disadvantages - more load to single belt, preferable to change tensioner simultaneously with the belt, inability to remove belt from one seized up unit (alternator, steering pump, compressor).


• The main mass defect of all AZ engines became apparent after few years of operation, and was more than critical. It is spontaneously destruction of the thread in holes for head bolts in the cylinder block, with seal failure, leaking of coolant through a gasket, possible overheating, mating surfaces warping etc.

And many owners and repairers initially did not allow the thought of constructive miscalculation of Toyota and believed that the failure of thread occurred due to overheating, whereas in reality it was the opposite.

Officially the problem was recognized in 2007, after some modifications (the length of the thread in the block have increased from 24 to 30 mm). Initially, manufacturer recommended to replace damaged blocks assembly (defective part numbers - 11400-28130, -28490, -28050, the price is $3000-4000). As warranty expired this method was unacceptable due to high cost, in practice the optimal was damaged thread reboring and threading to larger diameter to install threaded inserts for standard bolts (it is recommended to "update" all holes preventive, not damaged only, and renew the head bolts).

Finally, in 2011 Toyota officially recommended a special repair kit "Time Sert" with threaded inserts for post-warranty cars repair.

Modification of blocks with a slight increase of thread length was definitely effective - if "head drop" for 2000-2006 cars was only a matter of time, for later cars this defect become non-typical.

In comparison to this, the other possible faults perceived as trifles.

• Traditional for Toyota VVT problems with a knock after cold start (sometime with relative trouble codes). Manufacturer prescribed to replace VVT actuator (inlet camshaft sprocket) to the next update version.

• Unnatural noise from plastic intake manifold at idle or at light acceleration - prescribed to replace with modified.

• Usual problem of water pump leaking and noise. By analogy with other modern engines, the pump should be just considered as consumable with a life time about 40-60.000 km.

• Limited life time of alternator pulley clutch.

• Early versions had not the problem of high oil consumption for low mileage vehicles, but since type'2006 instead of problems with threads the problems with oil burning appeared (due to piston rings clogging). However, the damage from these defects is incomparable. Anyway, in case of oil consumption exceeded 500 ml per 1000 km manufacturer prescribed to replace the pistons (defective part numbers - 13211-28110, -28111) and piston rings.

• As for a gradual increase in oil consumption with the mileage, AZ series is not different from the classical Toyota's engines. Non-progressive consumption within the 200-300 ml / 1000 km under normal conditions can be considered acceptable (but during long rides with high rpm up to a litre consumption jumps are possible). In case of growing consumption may be recommended the overhaul with piston rings and valve seals replacement (with cylinder bore geometry check - that have been cases of ellipsoid formation without any wearing).

1AZ-FE (2.0 EFI)

1AZ-FE - transverse, with traditional multipoint injection, for initially FF cars and SUVs. Installed in: Avensis 250..270, Avensis Verso 20, Camry 30..40..50, RAV4 20..30, Wish 10. To end of the 2000s replaced by ZR series.

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 larger skirt.

- For some regions specific modifications was produced - for leaded gasoline, without VVT, without converter and relative components.

1AZ-FSE (2.0 D-4) / 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 cylinder head.

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

- The pistons has the specify shape which help to lead the fuel spray to the area of the spark plug. The top ring groove has anti-wear alumite coating.

- Some models was equipped with oil cooler.

1 - water pump, 2 - bypass, 3 - to heater, 4 - to radiator, 5 - from ATF heater, 6 - to ATF heater, 7 - thermostat, 8 - drain, 9 - oil cooler, 10 - from radiator.

- 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, other 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.

Fuel injection system (D-4)

1 - intake air temperature sensor, 2 - absorber, 3 - ETCS, 4 - EVAP VSV, 5 - fuel pump (low pressure), 6 - SCV VSV, 7 - manifold pressure sensor, 8 - supply pump, 9 - camshaft position sensor, 10 - ignition coil, 11 - VVT actuator, 12 - accelerator pedal position sensor, 13 - VVT valve, 14 - SCV valve, 15 - injector driver, 16 - injector, 17 - knock sensor, 18 - crankshaft position sensor, 19 - coolant temperature sensor, 20 - oxygen sensor, 21 - ECM, 22 - EGR valve, 23 - fuel pressure sensor, 24 - throttle position sensor, 25 - converter, 26 - NO-converter.

Early 1AZ-FSE was equipped with D-type control system (with MAP sensor), but Avensis 250 and some versions for domestic market since 2004 received L-type system with MAF sensor.

1 - intake air temperature sensor, 2 - absorber, 3 - ETCS, 4 - EVAP VSV, 5 - fuel pump relay, 6 - fuel pump (low pressure), 7 - manifold pressure sensor, 8 - supply pump, 9 - camshaft position sensor, 10 - ignition coil, 11 - VVT actuator, 12 - accelerator pedal position sensor, 13 - VVT valve, 14 - SCV valve, 15 - injector driver, 16 - injector, 17 - knock sensor, 18 - crankshaft position sensor, 19 - coolant temperature sensor, 20 - oxygen sensor, 21 - SCV VSV, 22 - ECM.

For traditional engine with multipoint injection optimal stoichiometric mixture ratio (mass air-fuel ratio λ) is 14.7: 1, the mixture leaner than 20-24:1 is not ignited by the spark plug.

The direct injection engine runs at ultra-lean mixture (λ = 30-40) - atomized fuel forms a cloud around the spark plug, and although in the whole combustion chamber mixture is very lean, near the spark it is close to the stoichiometric and can be ignited easily. Lean mixture in the remaining volume is less prone to detonation, which allows to increase the compression ratio and increase engine output. Due to the evaporation of injected fuel air charge in the cylinder is cooled further reduces the possibility of knocking and improves cylinder filling.

D-4 modes (domestic market)

1. Stratified combustion (LeanBurn). Implemented when driving at a constant speed and at low loads. Injection at the end of the compression stroke - the fuel is reflected from the recess of the piston, actively dispersed and vaporized, heading to the spark plug. Although the mixture in whole cylinder is lean (λ = 17-40), at spark plug area it is rich enough to be ignited by spark and fire the remaining volume.

2. Two-stage mixing. Implemented at mid-load for a smooth transition between modes of stratified and homogeneous combustion. Injection occurs twice - at intake and compression strokes, λ = 15-25.

3. Homogeneous combustion. Implemented when driving with load, during heating, at start, during brakes operation, during regeneration. Injection during the intake stroke, the fuel mixes with air and forms a homogeneous mixture with a composition close to the stoichiometric (λ = 12-15).

Fuel system

The fuel from tank pump (pressure ~400 kPa) supplied to high pressure pump, than under pressure into the fuel rail, and finally into the cylinders by injectiors

1 - fuel pump (low pressure), 2 - fuel pressure regulator, 3 - camshaft, 4 - pulsation damper, 5 - fuel pressure sensor, 6 - fuel rail, 7 - injector, 9 - supply pump, 10 - control valve, 11 - check valve, 12 - ECM.

Injection pump. Single-plunger with control valve, check valve and pulsation damper.

1 - supply pump, 2 - pulsation damper, 3 - from tank, 4 - relief valve, 5 - fuel rail.

- At inlet stroke the plunger moves downward and fuel draws into the pumping chamber.
- At the beginning of the compression stroke part of the fuel is returned while control valve is open (the specified fuel pressure is set in the range 8-13 MPa).
- At the end of the compression stroke control valve is closed and the pressurized fuel through the check valve is supplied into the fuel rail.

Fuel rail. Made of aluminium alloy, contains fuel pressure sensor to provide feedback, and a mechanical pressure relief valve (opens the drain line to the tank if the pressure exceeds 14 MPa).

1 - from supply pump, 2 - to tank, 3 - fuel rail, 4 - fuel pressure sensor, 5 - injector.

Injectors. Slotted injector nozzles produce fuel spray of various shapes (conical at homogeneous mode or narrow at stratified mode).

1 - retaining ring, 2 - O-ring, 3 - gasket.

Injector driver (EDU). The injectors are controlled by a driver, which converts the signal from the control unit (12 V) in the high-voltage signal to the injectors, ensuring maximum operation speed.

Air intake system

1 - SCV actuator, 2 - intake manifold, 3 - EGR valve, 4 - EGR manifold, 5 - ETCS.

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) function and some stabilization system (VSC) functions.

SCV (swirl control valve) actuator. There is 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. The flaps are driven by vacuum actuator.

1 - SCV actuator, 2 - SCV valve, 3 - MAP sensor.

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

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

EGR system (domestic market). Exhaust gas recirculation system of D-4 engines provides inlet of significant proportion of the exhaust gas at LeanBurn mode (much more than in traditional engines). It allows to low combustion temperature, decrease content of nitrogen oxides in the exhaust gases, reduce pumping losses at the inlet.

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

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

NOx-converter (domestic market). In the exhaust pipe of Japanese models NOx converter is installed. LeanBurn mode is accompanied by an increased emission of NOx, than 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). At homogeneous mode, with 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 with the accumulation of nitrogen oxides converter actively captures the sulphur, which takes the useful volume of the absorbent layer, so the system can to function normally only using low-sulphur gasoline.

Ignition system - DIS-4, spark plugs with iridium centre electrode (initially for overseas market - Denso SK20R11 / NGK IFR6A11, since MY2003 - Denso SK20BR11 with two additional side electrodes, for 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 throttle position sensor (Hall effect), absence of separate NO-converter.


• The above mentioned typical defects of 2AZ-FE engines are relevant for -FSE engines, including the problem with the "drop head" failure (defective parts - 11400-28120, -28160, ~$5000-6000).

In addition, several specific points are added:

• 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 is deteriorated. Often, the cause can not be found even by whole units replacement, although in some cases, cleaning of MAF sensor, throttle, SCV actuator, or replacement of VVT valve, ignition coil terminals, EGR forced clogging may be useful. To partially smooth discomfort from rpm subsidence helps replacement of the engine mounts (primarily - liquid filled).

• Direct injection and control system have 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), sometime injectors required in case of coil deteriorating. 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.

• EGR operation traditionally causes a strong carbon deposits 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 not EGR at -FSE engines for domestic market, but it does not eliminate the need for cleaning the intake of the oil sludge.


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 provides enough thrust-weight ratio (except perhaps medium-SUVs).

Direct injection. D-4 did not cause significant performance gain or improvement in fuel efficiency compare to conventional motors of AZ series, and performs primarily "environmental" objectives. But increased cost of maintenance and repair of the "excess" components is enough to once again make sure of 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 point of view of the manufacturer AZ considered "disposable", as well as all the modern engines without "oversize" concept. Of course, in despair, these engines are subjected to overhaul, with cylinder block liners replacement 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 complete overhaul 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 AZ series could be considered not bad representatives of the "3rd wave" motors, but 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 undermined confidence to even later modifications.

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