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Purchasing and Ownership Advice 

Buying advice on G50 Q45 (90-96)

By Wes Stinson
Edited by Jesda Gulati

Congratulations! You are looking at one of the finest cars ever created.  However, they are not without plenty of shortcomings.  Here are some major stats and facts about the 1st generation Q45.  A lot of my own personal opinion and experience is interjected, so if you don’t agree, sorry you didn’t take the time to write this article!  

  • They came stock with the VH45DE, and all aluminum powerplant, 4.5 liters, rated at 278hp/296ft/lbs of torque.  This is also one of the first cars to use VVT (variable valve timing), it controls the amount of intake valve overlap thus optimizing power.  That said, when they rated the VH45DE in 1989, in Japan, they rated the engine WITHOUT VVT.  In Japan, if an engine is rated over 280 horsepower, there is a stiff tax, so to avoid the tax they rated it without VVT installed (which consequently isn’t on the 96 model year, because of emissions regulations).  Thus, the engine produces closer to 310hp and 330ft/lbs of torque. 

  • These cars use one of the best paint processes in history.  You will be very hardpressed to find a Q with bad paint, unless it was completely abused.  They are also very resistant to rust.

  • IT was the first car to be offered with a FULL ACTIVE SUSPENSION.  Basically it is a computer controlled system, and a network of VERY COMPLEX hydraulic actuators, accumulators, and there is literally no roll inside .5g and they have that built in so drivers do not overdrive their tires.  New active computers can be purchased from Japan to make the active ride even better. 

  • It came with dual exhaust, 3 way catalyst system with ultra high flow cats.  Any exhaust modifications past removing and replacing the rear resonator is a measure in futility.  There is no power to be found in the exhaust system, and new catalysts are not recommended as they will not flow better than stock or last as long.

Variations of the Q45:


Q45a:  Designation for the Q45 with active suspension

Q45t: Touring model, minor differences except for upgraded wheels, and a rear sway bar.


Difference between the 90-93, 94-96; and problems associated with them


The first generation Q45 is said to be the best of a PERFORMANCE-LUXURY sedan, where performance is first and luxury is second.  The 90-93 is said to be the purest of these.  Real leather door panels, vinyl covered dash, some of the best plastics in the industry, and not a hint of bling-bling wood trim or anything like that. Everything was built for a purpose:  No grille because it creates wind resistance, no wood trim because its worthless, and so on.  There are many features that are only in the best of cars today.  I dare you to find EVERY interior feature in 20 mins in the first time you sit in a G50 Q.  The car also came stock to start in 2nd gear, to have really smooth starts, and then when you drop it to 1st, it unlocks the fury of the VH45. They used plastic where they shouldn’t have, and that’s the timing guides.  Unfortunately it’s a well researched and known ordeal, but not always known by many old Q owners. 


A description of the timing chain guide issue 

Defect:  On the slack side of the timing chain system, they used plastic backed timing chain guides.  What happens is they eventually crack, break, and this causes the chain to flop around, and it can and eventually will jump a few teeth.  The VH is an interference engine, and most of the time it completely destroys the engine.  However, this is only prevalent in mostly higher mileage engines.  Most failure are around the 120k range, and some have gone higher.  A friend of mine and fellow Q owner, Jesda, has a 92 Q45, that has 185,000 miles on his Q.  Just recently, he had his guides replaced.  Here is some pictures of his ordeal: .  He and the previous owners were VERY OCD about changing the oil (mobil 1 synthetic), and that is what I feel that saved his engine.  As you can see on the pictures, he was on borrowed time.  ALL 90-93 Q OWNERS, IF YOU THINK “THIS WONT HAPPEN TO ME” YOU ARE WRONG BECAUSE EVERY Q OF THIS ERA WILL FAIL AT SOME POINT IN TIME.  It is very unfortunate to see these engines go to waste, because they have only broken in by the time most have failed. 

Fix:  Metal backed guides were introduced.  You switch the old guides out.  If the guide pieces are missing, you MUST drop the oil pan and remove the old guide bits, because it will clog the oil pickup and possibly starve the engine for oil.  On an interesting note, by the time you’ve done 2 timing belt changes on a early Lexus LS400 you have already paid for the guide job on the Q, and you only have to do it once!


Other common issues:  Please see our TECH HELP section for more information

  • Injectors-  For some reason the injectors are weak on this car.  4 of them can be replaced with the plenum on (the silver “spider” atop the engine).  If the engine starts to shake at idle and you get a check engine light, most likely it is an injector.

  • MAF connector- Corrosion occurs on the connectors of the MAF, and causes a false reading, and ultimately a vibrating idle and driveability issues.  An easy way to test this is to wiggle the connector at idle, and it the idle changes then you must clean it. 

  • Transmission cooler- This is very prevalent on the 90-93.  The stock cooler is more of a “heater”.  An external cooler is recommended to prolong life, as the main killer of a transmission is heat and not wear.  The recommended cooler is a B&M part number 70268, and can be had at for about $60.  See for installation instruction. 

  • Knock sensors- The case of the knock sensors eventually crack and fail (usually around 120k) and this causes the computer to retard the timing 5* or so, causing decreased acceleration.  If this is the case, you get to remove the plenum.



Everything is applicable except for the following changes:

  • The timing guide issue is not applicable, they came with the updated guides

  • A softer suspension for a better ride (but in my opinion still very stellar handling)

  • Softer seats, traction control and other interior accents were added.

  • Exterior styling, with a grille and some other minor things.

  • Power headrests and tilt down mirrors in reverse

  • 1st gear starts were now standard, and a lowered 1st and 2nd gear to maintain smoothness

Basically all off the same issues EXCEPT the guides are there, except not really as bad.  Injectors were restyled and are more reliable, but they still fail, especially in areas with iffy gas, California and Arizona being the worse.  In most peoples opinion, these are overall the best Q45s to get because of the better reliability and lower cost to own, and more luxury.  However its not by any stretch of the imagination gone drastic changes, its still very much a drivers car.

The 96 model year got OBDII (on-board diagnostics) and lost variable valve timing as a shortcut to meeting emissions standards, thus much closer to advertised horsepower and torque (actual power output is higher than advertised).

What to look for when buying a 90-96 Q45.


First thing is to visually inspect the exterior.  Look for variations in the paint (there should be little orange peel, if any).  If there is, its probably been repainted at some point.  There’s only one common rust area on the Q, and that is on the rear, where the plastic bumper meets the rear quarter panel.  Its uncommon to see a Q with exterior rust, and if there is run away, because it probably hasn’t been maintained well.   However its just that small spot I wouldn’t worry too much.



Just make sure everything works.  Don’t worry about any STOP LAMP INOPERATIVE messages or something similar to that because they can all be fixed easily.  Be concerned if it does say TRANSMISSION MALFUNCTION.


Something Ive noticed on many Q is the little interior lights go out.  I have many out in my Q right now.  They go behind many switches and there are tons of them.  Another thing like that is the rear ash trays, most flop around and are broken.



There are many things with the Q engine that can be easily inspected.  A look inside the oil filler cap is worth 1000 words.  You need to really look down in there with a flashlight as far down as you can see, and you should only see cleanness.  If its black or really dark brown stay away.


Check the engine oil.  The level should be good, and the oil a nice golden color if its been recently changed.  When you wipe it off, in the little round part of the stick, there should be no goo there. 


Other fluids:  Brake fluid (should be clear; slightly yellow); transmission fluid (red, and should NOT be brown or smell burnt); powersteering fluid (same as tranny fluid).


With the engine running at idle, you should feel no vibrations, it should run about 650rpm fully warmed (just below the line between 500 and 1000).  If its below this then the intake will need cleaning, and do NOT ADJUST THE IDLE SPEED, it needs to be corrected by cleanliness.  You shouldn’t really hear much, you will here some slight ticking of the injectors opening.  Its very soft and anything else should be taken note of.  The fan should show resistance when moved  (engine off).


On the lift

Check for body damage, rust, and other damage.  Also check the suspension components, namely the rubber bushings for leaking of silicone or cracking.  They are used with age and not with miles.

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