Ls400 Fuel Consumption Problem

kristoff · February 3, 2014

Hi again guys,

I have 1993 LS400 engine and gearbox in my toyota hilux.

I love the engine and the way it works.

but recently fuel consumption gone through the roof. I know it is a truck with aerodynamics of a brick but still....

anyway...

truck was due its MOT...failed due to high emissions. cut off point was at 3.50% and mine reading was something like 8.90% - 9.20%

wet to local lexus toyota specialists...sorted the problem! faulty cable/connection on air mass flow sensor. technician said that he is not sure about the sensor itself.

...MOT retake ...passed with 2.60% :D

but...then I've decided to check properly my mpg as should be much better now, right?

nope! getting about 7-8 mpg :o

is there any sensor or anything that could be the reason for this poor fuel economy???

cheers!

Bluesbreaker · February 4, 2014

Hey Kristoff-bet that truck pulls well with a load! any chance of some photos of the LS 400 engine in your truck?

mikeyv · February 4, 2014

Gearing + extra fuel for 4X4 maybe?

Our taxi firm once had a Cortina 1.3 base model which had a 1.6 engine only transplant, went like stink from a standstill, but was dreadful at cruising speed(too many revs), and shockingly bad on fuel, even by old Fords standards.

Needless to say, it wasn't long before it went bang, followed by a one way trip to the scrappers.

It was obvious on that car that the engine didn't match the transmission, but maybe with a big lazy V8, it wouldn't be as noticeable, other than through the fuel consumption?

munday · February 4, 2014

Most likely sensor to be at fault is the ECT sensor (engine coolant temperature). It is one of the main inputs for the ecu to decide fuelling along with lambda and airmass.

You can even check the current one as the workshop manual lists the resistance for a range of temperatures. TBH its a cheap sensor anyway to replace so its probably worth doing

kristoff · February 4, 2014

Hey Kristoff-bet that truck pulls well with a load! any chance of some photos of the LS 400 engine in your truck?

yeah mate! goes well ;) some pics

Most likely sensor to be at fault is the ECT sensor (engine coolant temperature). It is one of the main inputs for the ecu to decide fuelling along with lambda and airmass.

You can even check the current one as the workshop manual lists the resistance for a range of temperatures. TBH its a cheap sensor anyway to replace so its probably worth doing

that is what I thought. cheers

any idea where I can get one? having trouble to get my hands on genuine part. couldn't get hold of local dealer either.

are aftermarket sensors ok?

munday · February 5, 2014

I would only go with genuine tbh mate, I don't trust the copies. Your local lexus/toyota dealer (once you get through to them) should be able to sort it out. If you have access to toyodiy.com you can find the part number there (if you weren't a member before 2009 you need a special invite from an existing member before you can view the diagrams, give me your email address via PM and I can do that)

kristoff · March 5, 2014

replaced the sensor....no change. still 8mpg :(

is there anything else that could cause this?

steve2006 · March 5, 2014

You did replace the correct one?

There are 2 one for the ECU and one for the Gauge,IIRC the correct one has the green socket connection.

kristoff · March 5, 2014

You did replace the correct one?

There are 2 one for the ECU and one for the Gauge,IIRC the correct one has the green socket connection.

hey steve,

yes that is the one ;)

Alfie B · March 5, 2014

What sort of RPM are you doing at cruising speed ? I have a customer who also put a Mk1 engine & box in a surf and also had poor economy, the fault was a sensor that stopped it from going into top gear when it's warmed up .. A bit like driving a manual in 3rd .. I don't know which sensor it was but he said it was common on a lot of Jap's

kristoff · March 5, 2014

to be honest I didn't had a chance to go outside the city for a while. I know that mpg will be worse around town but shouldn't be that bad.

I cant really tell you but gears seem to work ok, including overdrive. I have 4.56 diff ratios so technically good for cruising but bad for getting off the line. Still don't think that this should make such a difference.

Foulsbane · March 6, 2014

When I wanted a replacement sub woofer speaker I found a brand new one via CTP

(Cheap Toyota Parts)

Redsteve · March 7, 2014

Hello Kristoff,

I used to run a Rover 3.5V8 in a HiLux (Mk3) and I used to get about 15 MPG on 33 inch tyres.

I am not sure if the 4X4 system on your HiLux is the same but I had manual locking front hubs.

If I left the front hubs locked up then the MPG used to go through the floor.

If yours is the same it might be worth checking that the hubs are unlocked, and if they are unlocked, actually checking that they have unlocked by jacking up the front end and spinning the wheels. If the front wheels are unlocked then the front propshaft should not turn.

I hope this helps.

Steve

kristoff · March 7, 2014

Hello Kristoff,

I used to run a Rover 3.5V8 in a HiLux (Mk3) and I used to get about 15 MPG on 33 inch tyres.

I am not sure if the 4X4 system on your HiLux is the same but I had manual locking front hubs.

If I left the front hubs locked up then the MPG used to go through the floor.

If yours is the same it might be worth checking that the hubs are unlocked, and if they are unlocked, actually checking that they have unlocked by jacking up the front end and spinning the wheels. If the front wheels are unlocked then the front propshaft should not turn.

I hope this helps.

Steve

hey steve,

cheers will check that but I am pretty sure they are unlocked.

are you in HPOC? ;)

Redsteve · March 8, 2014

kristoff, on 07 Mar 2014 - 21:55, said:

kristoff, on 07 Mar 2014 - 21:55, said:

Hello Kristoff,

I used to run a Rover 3.5V8 in a HiLux (Mk3) and I used to get about 15 MPG on 33 inch tyres.

I am not sure if the 4X4 system on your HiLux is the same but I had manual locking front hubs.

If I left the front hubs locked up then the MPG used to go through the floor.

If yours is the same it might be worth checking that the hubs are unlocked, and if they are unlocked, actually checking that they have unlocked by jacking up the front end and spinning the wheels. If the front wheels are unlocked then the front propshaft should not turn.

I hope this helps.

Steve

hey steve,

cheers will check that but I am pretty sure they are unlocked.

are you in HPOC? ;)

Hello Kristoff,

I used to post on HPOC and, as far as I know, I am still a member but I haven't posted for a very long time.

There was a bit of a falling out among some members and a new club called Elite 4X4 was formed.

I found that the guys that went to Elite were much more relaxed so I posted there for quite a while but I haven't been on the site for a long time now.

I still have a HiLux (the one in my avatar) but all my buddies got rid of their 4X4s so I don't go off-roading now.

The truck that had the V8 was a much nicer looking one than I have now.

Steve

kristoff · March 10, 2014

kristoff, on 07 Mar 2014 - 21:55, said:

kristoff, on 07 Mar 2014 - 21:55, said:

Hello Kristoff,

I used to run a Rover 3.5V8 in a HiLux (Mk3) and I used to get about 15 MPG on 33 inch tyres.

I am not sure if the 4X4 system on your HiLux is the same but I had manual locking front hubs.

If I left the front hubs locked up then the MPG used to go through the floor.

If yours is the same it might be worth checking that the hubs are unlocked, and if they are unlocked, actually checking that they have unlocked by jacking up the front end and spinning the wheels. If the front wheels are unlocked then the front propshaft should not turn.

I hope this helps.

Steve

hey steve,
cheers will check that but I am pretty sure they are unlocked.

are you in HPOC? ;)

Hello Kristoff,
I used to post on HPOC and, as far as I know, I am still a member but I haven't posted for a very long time.

There was a bit of a falling out among some members and a new club called Elite 4X4 was formed.

I found that the guys that went to Elite were much more relaxed so I posted there for quite a while but I haven't been on the site for a long time now.

I still have a HiLux (the one in my avatar) but all my buddies got rid of their 4X4s so I don't go off-roading now.

The truck that had the V8 was a much nicer looking one than I have now.

Steve

Hi Steve,

Yes I heard about that. But I became member after. There still is nice bunch of people there. Lots of meets and banter. ;)

You have any pix of your old v8? :)

Cheers

Redsteve · March 10, 2014

kristoff, on 10 Mar 2014 - 15:17, said:

kristoff, on 10 Mar 2014 - 15:17, said:
kristoff, on 10 Mar 2014 - 15:17, said:
kristoff, on 07 Mar 2014 - 21:55, said:

kristoff, on 10 Mar 2014 - 15:17, said:
kristoff, on 07 Mar 2014 - 21:55, said:

Hello Kristoff,

I used to run a Rover 3.5V8 in a HiLux (Mk3) and I used to get about 15 MPG on 33 inch tyres.

I am not sure if the 4X4 system on your HiLux is the same but I had manual locking front hubs.

If I left the front hubs locked up then the MPG used to go through the floor.

If yours is the same it might be worth checking that the hubs are unlocked, and if they are unlocked, actually checking that they have unlocked by jacking up the front end and spinning the wheels. If the front wheels are unlocked then the front propshaft should not turn.

I hope this helps.

Steve

hey steve,
cheers will check that but I am pretty sure they are unlocked.

are you in HPOC? ;)

Hello Kristoff,
I used to post on HPOC and, as far as I know, I am still a member but I haven't posted for a very long time.

There was a bit of a falling out among some members and a new club called Elite 4X4 was formed.

I found that the guys that went to Elite were much more relaxed so I posted there for quite a while but I haven't been on the site for a long time now.

I still have a HiLux (the one in my avatar) but all my buddies got rid of their 4X4s so I don't go off-roading now.

The truck that had the V8 was a much nicer looking one than I have now.

Steve

Hi Steve,

Yes I heard about that. But I became member after. There still is nice bunch of people there. Lots of meets and banter. ;)

You have any pix of your old v8? :)

Cheers

Hi Kristoff,

I only have one picture of the old V8 and that doesn't show the engine, it was back in the days of 35mm film so it was expensive taking pictures back then. :winky:

In contrast, this is my current truck.

And this is the last HPOC meeting I went to at Tixover, near Peterborough.