Important Advice For Those Who Have A Higher Mileage Gs300

[maneesh]

I have reviewed my fuel costs after 11,000 miles in my GS. Average mpg works out at 20mpg, which is lower than what it should be.

Have serviced the car, no check engine lights have appeared. Everything appears to be in order.

I got my codes read on Saturday, turns out my oxygen sensors are :tsktsk:

Worn oxygen sensors lead to poor mpg (up to 30% more fuel used), and poor performance. They can wear out after just 60-70k miles. Mine is now 95k.

Replacing oxygen sensors is a DIY job, and I'm buying mine from the US for 30 quid each.

I feel like such a stupid person, as I've spent £750 MORE on petrol this year, that I didn't need to, if I had pulled the codes when I bought the car.

Learn from my experience, and if you're driving an older GS (or even LS), get your diagnostic codes checked to see if your oxygen sensors are worn out..could save you a packet in petrol!!!

[P4UL T]

I know I replaced one about a month back,

got it from www.oxygensensors.com and done it myself, give us a shout if you need any help.

Shortly after replacing it, I done an a 100 mile motorway trip doing 70 the whole way I averaged 34mpg!!!

[aido]

Mega, cheers for the PM Maneesh, will look into this mate, sounds like I'm seeing the same sort of behaviour in the Aristo!

[peter026]

Nice one maneesh, will get mine checked.

[P4UL T]

There are four on the mk2 GS the three you can see in the diagram and the fourth is after the main cat

[IanCornwall]

I took mine off today as I dismantled to get my cylinder head off in case they got knocked and damaged when the exhaust came off

First I had the air intake tubing out of the way, simple enough with a 10 mm socket

Next the heat shield was a doddle, 4 or was it 5 nuts, 12 mm socket

lift the heat shield out of the way

Now it is easy to see the Oxy sensors, 2 x 12 mm socket on the nuts each simply undo and it pulls out

The hardest bit was getting the cable connectors to let go, I guess a few years grit and muck in the release doesn't help

Seems 95% of the engine is undone with 10mm and 12mm sockets

Now I have mine out, is there an easy way to check them ? or is it wait until they are back in and trundle down to Lexus for a diagnostic ? and if so what is the normal charge for a diagnostic check up ?

[P4UL T]

Diagnostics is done with the sencors intact in the car.

Mine screwed straight into the maniflod, need a special tool or a big wrench, not 12mm nuts

[maneesh]

Now I have mine out, is there an easy way to check them ? or is it wait until they are back in and trundle down to Lexus for a diagnostic ? and if so what is the normal charge for a diagnostic check up ?

you need a multimeter to check out the voltage going thru the multimeter. not entirely sure how to connect up, i believe the factory service manual gives tips, but I don't have that!!!

[maneesh]

Lexus GB want 360 quid for 2 main oxygen sensors... :tsktsk: :tsktsk: :tsktsk:

yay! just ordered 2 universal sensors from the states for 70 quid.. :o

[fatpieman69]

what about the IS, would it affect the IS?

Craig

[maneesh]

what about the IS, would it affect the IS?

Craig

I assume so, nearly every car has oxygen sensors

[piperdog]

surely it will only list them as a fault when there not working,not when theyre inefficient ?

[ColinBarber]

you can test O2 sensors for reaction speed. You need either a good OBD-II reader or an oscilloscope and a can of propane to make the air/fuel mixture rich.

The sensors can become dirty and can be cleaned with a blow torch. Only when the heaters fail or the sensor becomes very bad will it trigger an error code.

Be careful with the RX300, ES300 as this engine uses air/fuel ratio sensors rather than standard O2 sensors - if replacing you need to get the correct sensor.

There is a section on testing O2 sensors half way down this page:

http://www.troublecodes.net/articles/catfailure/

[Ryo]

where are they on a mk1?, had a look can only find on that looks sorto like it on the exhaust manifold

i think mines drinking alot of fuel 150 miles to half o tank,

(mileage 120 odd thousand)

Steve

[Simon Hornby]

where are they on a mk1?, had a look can only find on that looks sorto like it on the exhaust manifold

i think mines drinking alot of fuel 150 miles to half o tank,

(mileage 120 odd thousand)

Steve

Just had a look on my mk1 - I am gonna do this one myself and the sensor is very accessible!!! My Fuel consumption is plain unacceptable!! Ok I have an old car but It has been well maintained so I do not see any reason why it can't perform close to spec. To chage the senor looks like a 30 minute job which usually means it will take all day - but hey, think of the savings!!!

I'll also use 10w30 (allowed according to the handbook) and bung in some ptfe like slick 50, maybe even a K&N - I'll get this bloody thing doing at least 25mpg if it kills me!!

[craig7022]

Cheer Maneesh,

Going to get mine checked at the next service in a couple of weeks.

I get about £450ish miles to a tank is that good???

Maybe we could do a group buy on this sort of thing!!!

Regards Craig

[Ryo]

450 miles craig is alot better than me, , its like just under 1/2 i get 200 miles then it seems to drop like a stone, and i drive like an old man

i think ill def get a new one of these. might even help the slight erratic running i got aswell (everything else OK plugs N stuff)

[ColinBarber]

I'll also use 10w30 (allowed according to the handbook) and bung in some ptfe like slick 50, maybe even a K&N - I'll get this bloody thing doing at least 25mpg if it kills me!!

I wouldn't use slick 50, it's too expensive. £20 for the product and £3000 for a new engine!

[randyreindeer]

keep us posted on how the MK1 performs with a change of sensor.

[C4MYC]

I have reviewed my fuel costs after 11,000 miles in my GS. Average mpg works out at 20mpg, which is lower than what it should be.

Have serviced the car, no check engine lights have appeared. Everything appears to be in order.

I got my codes read on Saturday, turns out my oxygen sensors are :tsktsk:

Worn oxygen sensors lead to poor mpg (up to 30% more fuel used), and poor performance. They can wear out after just 60-70k miles. Mine is now 95k.

Replacing oxygen sensors is a DIY job, and I'm buying mine from the US for 30 quid each.

I feel like such a stupid person, as I've spent £750 MORE on petrol this year, that I didn't need to, if I had pulled the codes when I bought the car.

Learn from my experience, and if you're driving an older GS (or even LS), get your diagnostic codes checked to see if your oxygen sensors are worn out..could save you a packet in petrol!!!

Hey Pimp.....how you doin` these days.

Interesting post mate.

Well I have the same problem with my GTO and am expecting my universal (well I wasn`t going to Mitsustealer for it) sensor tomorrow. 50 pounds delivered including the special spanner.

I would say that we should change the sensors every say 25k miles as a force of habit because they`re gonna be on their way out by then anyway due to the very nature of their location.

Andy

[blackrat300]

Hi

My friend has an all singing obd2 diagnostic, what do failing or low performing oxy sensors show up as?. my 96 gs300sport is only doing 19mpg on a 10 commute on empty road at sub 50mph!

thanks

[maneesh]

obd2 diagnostics wont work with your 96 car as yours is obd1. you need to bridge the terminals of the diagnostic port (t1 and e1, with a paperclip) and then switch ignition on and count the number of flashes on dashboard of check engine light, that will give you the error codes stored.

yes from the sounds of it, your o2 sensors could be knackered..

[genius149]

Excuse my ignorance at this late hour, but would this have any affect on my gas powered beast?

[DeanoC]

Depends how it is configured, if the fueling is controlled by the stock ECU then yes. or if the new ECU is wired upto the lambda sensors then yes. Im not really sure how LPG is fitted to be honest.

Its just open loop and closed loop. If your o2 sensors are goosed they will either provide false readings or the ECU wont use them to determine how to adjust the fueling at all it will just use the lookup tables on the ECU. This is never spot on as its just a generic set.

Hence you loose bhp and mpg.

I wouldn't go more than 30k without giving them a check and clean at least. They are relativley cheap, easy to check / replace and really do make a dramatic impact on the running on the car.

If your cars obd 1 then you can test them with a blowtorch and a multimeter but it may just be better to buy new ones :)

[Kazi]

Anyone know where and how much they are for the IS?