Mk1 Gs300 Sport - Rather Slow

[Fire99]

Hi people,

well i've had my '95 GS300 Sport for a few weeks now and its a great comfy car but i am experiencing a couple of issues which may be linked..

Notably i seem to get 21mpg regardless of how i drive it and includes quite alot of dual carriageway work.. i mostly cruise around 80mph and have been driving gently to try and get the mpg up a little..

The other issue is the car seems pretty sluggish.. Its ok from a standstill (which i thought is where it would struggle with its weight etc) but once on the move (50-60mph) it seems you have to bury the throttle and kick down to get any kind of decent progress.

So far i've replaced the front disks and pads (as were getting low) and serviced the calipers so i dont have any sticking issues.

Oil and filter has been done along with a new air filter.

I've reset the ECU as advised on here (many thanks people) and i've checked my ECU for fault codes with the trusty paperclip but all appears ok.

The car is on 113k so not huge mileage. Also the car runs smoothly with no misfires in the rev range.(so i dont suspect bad leads or plugs) Just very sluggish.

I've read with great interest people talking on here about the O2 sensors but no-one has reported (from what i can see) that their cars have actually driven alot brisker than before replacing them.

So im rather at a loss...

Any suggestions please people?

many thanks,

Nick

[shake]

hi

with mpg you cant expect much. its an old engine (technology wise). driving at 70mph uses less petrol than when crusing at 80. i've found driving in snow mode helps with mpg.

at the end of the day we've got motorway cruisers not race cars. most torque is produced at 4k-5k rpm. i kinda know what you mean when you say you have to bury your foot around the 60mph mark, i reckon theres a flat spot there. although i've noticed when in pwr mode the car holds revs longer so when you want to go theres no kick down as its in the suitable gear already ... the car also has a learning ecu... if you drive gently to save fuel it will learn this and help so to speak... drive it hard for awhile and it acts more potent!

the best bang for buck in my opinion is TESCO 99RON PETROL!!!! (also get more miles out of it)

what petrol do you use?

[Fire99]

hi

with mpg you cant expect much. its an old engine (technology wise). driving at 70mph uses less petrol than when crusing at 80. i've found driving in snow mode helps with mpg.

at the end of the day we've got motorway cruisers not race cars. most torque is produced at 4k-5k rpm. i kinda know what you mean when you say you have to bury your foot around the 60mph mark, i reckon theres a flat spot there. although i've noticed when in pwr mode the car holds revs longer so when you want to go theres no kick down as its in the suitable gear already ... the car also has a learning ecu... if you drive gently to save fuel it will learn this and help so to speak... drive it hard for awhile and it acts more potent!

the best bang for buck in my opinion is TESCO 99RON PETROL!!!! (also get more miles out of it)

what petrol do you use?

Hi there,

yeah i kinda guessed it being effectively the last series N/A Supra engine it would be fairly old school.. (Iron block straight 6 and all that)

I'm running Esso normal 95 ron. when you're churning it up at 20-21mpg you tend to go for the cheapest.. :-)

I've just heard of people getting mid to late 20's on a run and i see nothing like that..

On the performance front i didnt expect it to be startling but i've struggled to keep up with even pretty mediocre cars and that hurts somewhat when they are doing 30-40mpg+ and im doing 20...

Could be a very short love affair with the lexus at this rate :(

[TigerFish]

I've found the air filter has made a huge difference on mine. I've just fitted a K&N panel filter and have noticed a marked improvement in MPG even compared to mileage just after changing for an OEM filter. Sitting at 70 on the motorway I now get 33mpg (not tried 80 but i wouldn't expect it to be a long way off the 33 at 70 from previous checks before) and average 26 on mixed driving. This is about 10% above what the OEM filters were getting just after being changed. Consumprion dropped of quite quickly I found with the OEM filters as they clogged. I would think the 02 sensors could do with looking at as the next step. I'm not sure what fault codes if any would appear if an 02 sensor has not completely failed.

I would tend to think that the performance issue is more getting used to how the car works. If you are saying you plant the accelarator and kick down, and the car is performing as you would expect then I can't see that it can be anything else. If you plant, kick down and the car is going nowhere, then it could be the car, but I don't think that is what you are saying Are you using the ect/pwr mode? This does make a massive difference on mine to how responsive it feels. In normal mode, the gearboxes eagerness to keep revs as low as possible is extremely annoying and the amount of kick down required to get it going again is sometimes quite worrying. i.e. kicking down from say 4th to 1st has an horrendous delay which can make you feel stranded if you have pulled on to a roundabout quickly but had to let up slightly. Before you know it you are in 4th and the car doesn't want to make haste again quickly. ect/pwr mode solves all of that so I tend to not have it in any other mode.

Shake, no snow mode on our older GS's mate :(

[Fire99]

I've found the air filter has made a huge difference on mine. I've just fitted a K&N panel filter and have noticed a marked improvement in MPG even compared to mileage just after changing for an OEM filter. Sitting at 70 on the motorway I now get 33mpg (not tried 80 but i wouldn't expect it to be a long way off the 33 at 70 from previous checks before) and average 26 on mixed driving. This is about 10% above what the OEM filters were getting just after being changed. Consumprion dropped of quite quickly I found with the OEM filters as they clogged. I would think the 02 sensors could do with looking at as the next step. I'm not sure what fault codes if any would appear if an 02 sensor has not completely failed.

I would tend to think that the performance issue is more getting used to how the car works. If you are saying you plant the accelarator and kick down, and the car is performing as you would expect then I can't see that it can be anything else. If you plant, kick down and the car is going nowhere, then it could be the car, but I don't think that is what you are saying Are you using the ect/pwr mode? This does make a massive difference on mine to how responsive it feels. In normal mode, the gearboxes eagerness to keep revs as low as possible is extremely annoying and the amount of kick down required to get it going again is sometimes quite worrying. i.e. kicking down from say 4th to 1st has an horrendous delay which can make you feel stranded if you have pulled on to a roundabout quickly but had to let up slightly. Before you know it you are in 4th and the car doesn't want to make haste again quickly. ect/pwr mode solves all of that so I tend to not have it in any other mode.

Shake, no snow mode on our older GS's mate :(

33mpg???? holy mackerel. Honestly, even driving like 'Miss Daisey' i managed to creap up to 21.5mpg. 33 would be a miracle..

Well its not bad on kick down but nothing special. I dont cruise around in pwr mode because obviously MPG is pretty dreadful anyway and leaving it in pwr mode would just make it worse..

I'll replace the O2 sensors and maybe try a K&N before i give up and go back to the 'german side of the force'.. shhhh dont tell anyone..

[TigerFish]

I dont cruise around in pwr mode because obviously MPG is pretty dreadful anyway and leaving it in pwr mode would just make it worse..

Might be worth trying the ect/pwr mode for a while. There have been a couple of threads regarding economy and the power mode. I don't notice a big difference, maybe because the gearbox is more will to change gears in power you get a trade off. There are quite a few big hills I go up and down on the way to work. In normal mode, going up the hill I have the throttle almost to the floor to maintain the 60/70 going up the hill (and it still wont drop down a gear). In power mode, just a slight press of the throttle drops a gear and it maintains the speed without planting the throttle mostly to the floor. So I must be gaining in that situation I would think.

Try reading through this thread regarding the 02 sensors clicky

[dave1]

Mine gives 28/31 on motorways @ 70ish. 15/20 round town depending on my right foot. 20/25 mixed driving. I always brimfill to keep check on my MPG figures.

No power issues, it is very quick off the mark even with a very light touch on throttle and plenty of power through the range. Even at 70 it pulls very quickly if pulling out to overtake.

I assume you have got your overdrive switched on?

Regards Dave

[shake]

despite the lack of miles i get on the gs, im extremely happy with its performance. off the line acceleration no one sees it coming.

are your tyres at the correct psi? makes a huge difference to performance and mpg.

[Fire99]

hi guys,

well i've checked tyre pressures after a chat with a few people on here and am running 34psi allround on the 18" sport wheels..

I read the Oxygen Sensor thread with great interest but we never heard in the end what the final result was with regards to fuel economy and performance. The original poster seemed to go quiet at that point...

I've found some very cheap sensors on eBay (new universal 4 wire ones) and may give it a try..

I dont have a workshop manual for the Lexus but does anyone know what the timing should be? May be worth giving that a check since it seems to use conventional distributor ignition..

Currently £30 of 1.04 unleaded will do anything between 110 and 130 miles.. even driven like captain snail in snailville

[TigerFish]

This is what it says in my electronic manual for timing adjustment (Note that this is an american version but would assume ignition timing would be the same??)

IGNITION TIMING INSPECTION AND

ADJUSTMENT

EG4MC–01

1. WARM UP ENGINE

Allow the engine to warm up to normal operating temperature.

2. CONNECT TACHOMETER AND TIMING LIGHT TO

ENGINE

Connect the tester probe of a tachometer to terminal IG􀀀 of

the DLC1.

NOTICE:

• Never allow the tachometer terminal to touch ground as

it could result in damage to the igniter and/or ignition

coil.

• As some tachometers are not compatible with this

ignition system, we recommend that you confirm the

compatibility of your unit before use.

3. CHECK IDLE SPEED

(See step 3 in idle speed inspection)

4. ADJUST IGNITION TIMING

(a) Using SST, connect terminals TE1 and E1 of the DLC 1.

SST 09843–18020

(B ) Using a timing light, check the ignition timing.

Ignition timing: 10° BTDC @ idle

(Transmission in neutral position)

© Loosen the nut, and adjust by turning the distributor.

(d) Tighten the nut, and recheck the ignition timing.

Torque: 19 NVm (195 kgfVcm, 14 ftVlbf)

(e) Remove the SST from the DLC1.

5. FURTHER CHECK IGNITION TIMING

Ignition timing: 7–19° BTDC @ idle

(Transmission in neutral position)

EG–16

ENGINE – ENGINE MECHANICAL

HINT: The timing mark moves in a range between 7° and 19°.

6. DISCONNECT TACHOMETER AND TIMING LIGHT FROM

ENGINE

There is definately something effecting the mpg badly, I've just driven down from Derby to Dorking on £25 (152miles @ 29.8mpg).

[Fire99]

This is what it says in my electronic manual for timing adjustment (Note that this is an american version but would assume ignition timing would be the same??)

IGNITION TIMING INSPECTION AND

ADJUSTMENT

EG4MC–01

1. WARM UP ENGINE

Allow the engine to warm up to normal operating temperature.

2. CONNECT TACHOMETER AND TIMING LIGHT TO

ENGINE

Connect the tester probe of a tachometer to terminal IG􀀀 of

the DLC1.

NOTICE:

• Never allow the tachometer terminal to touch ground as

it could result in damage to the igniter and/or ignition

coil.

• As some tachometers are not compatible with this

ignition system, we recommend that you confirm the

compatibility of your unit before use.

3. CHECK IDLE SPEED

(See step 3 in idle speed inspection)

4. ADJUST IGNITION TIMING

(a) Using SST, connect terminals TE1 and E1 of the DLC 1.

SST 09843–18020

(B ) Using a timing light, check the ignition timing.

Ignition timing: 10° BTDC @ idle

(Transmission in neutral position)

© Loosen the nut, and adjust by turning the distributor.

(d) Tighten the nut, and recheck the ignition timing.

Torque: 19 NVm (195 kgfVcm, 14 ftVlbf)

(e) Remove the SST from the DLC1.

5. FURTHER CHECK IGNITION TIMING

Ignition timing: 7–19° BTDC @ idle

(Transmission in neutral position)

EG–16

ENGINE – ENGINE MECHANICAL

HINT: The timing mark moves in a range between 7° and 19°.

6. DISCONNECT TACHOMETER AND TIMING LIGHT FROM

ENGINE

There is definately something effecting the mpg badly, I've just driven down from Derby to Dorking on £25 (152miles @ 29.8mpg).

Thanks alot for posting all that info.. Yeah sounds like something is upsetting the MPG in a big way..

Well i think O2 sensors will have to be the next course of action as i would imagine the car is on the original ones at 110k+ miles.

thanks again for your efforts.

Nick

[shake]

re igintion timing > i wouldnt adjust the timing until you find out exactly what it is ment to be and what you can adjust it to. usa run lower ron than us, whether that would of made a difference to the set degrees i dont know, but someone should on this site!

also find out how to retard the timing before adjusting it yourself.

i found advancing the timing on my previous car beneficial but using 95ron was a big no no. had to be 99ron! car had a spring in its step and got more mpg!