1uz Hilux with Crown ECU - Bad fuel economy

[jeremy]

We have a ls400 1uz in our hilux that was wired up by a sparkie to the crown ecu. Fuel economy is currently at approx 28L/100km (or 10mpg) when driving conservatively, no diag codes.

Where should I start looking?

EDIT: I know of another 1uz hilux that was wired up by the same guy with the same fuel economy problem. Any clues would be greatly appreciated.

 

[sideshow]

10mpg

its a tad too much

check your oxygen sensors or clean yr air lfow meter


i have a hilux with 50lt tank and i get 290 to 300 kms per tank

they are not so good on fuel especially if u have an auto gbox

i just tell people to get over it and put up with it

i used to get 360 kms per tank but i changed from 4.3 to 3.7 diff

so the less revs u do when driving means more load on enigne so it uses more fuel

they get goo dkms on the highway or in a soarer with a massive tank

but in a hilux with the pissy 50 lt tank

its crap

 

[Peewee]

My Celsior uses less than 10L/100km on the open road, cruising at 105kph with the aircon on.
14L/100km around town/suburbs with the aircon on.


There are many reasons to be using that much fuel. You need to find a car (that runs fine) running the same ecu as yours and start swapping things.
ECU, AFM, Water temp sensor.

Maybe start by putting the car on a dyno and seeing the power output.
If its really low, then there is a chance the ecu is in Limp Home mode, and the timing is locked at 10deg.

 

[jeremy]

Ok, thanks guys that gives me a few places to start looking.

I should have mentioned that the 28l/100km was worked out on very conservative highway driving not even doing 100kph most of the way (I was following someone)

We have the standard Lexus auto with 4.88 diff ratios and 35" Simex tyres - so we do realise that fuel economy is never going to be like the standard car, but it still seems to be using much more than it should after having talked to others who run a similar setup and use no where near that amount of fuel.

We're running the standard LS400 fuel tank which seems to be 75ish litres, but don't know what sort of mileage we'd get out of a full tank as we never really drive it until empty as it's just our weekend toy.

Maybe start by putting the car on a dyno and seeing the power output.
If its really low, then there is a chance the ecu is in Limp Home mode, and the timing is locked at 10deg.

Will timing be at 10deg in limp mode? I read on another thread that it would be at 5deg at idle but normally is 18-19deg - is that right or is for another ECU (not the Crown)?

 

[Peewee]

I've never had my car in limp mode but from what I've been told its 10deg, regardless of rpm.

 

[hi-lex]

I have had this with a couple of my conversions and it was oxy sensors both times

 

[jeremy]

Haven't done much on this yet, been to busy driving the thing to work on it! But I did check the timing and it seems to be around 16-17ish degrees at idle so appears not to be in limp mode.

While having a quick look around, I did notice that the oxygen sensors aren't wired up. So that could be the cause right? Would having no oxy sensors cause it to run rich? If so, I'll have a go at wiring them in and see how things go.

 

[sideshow]

you would think so being they are the main adjustment for fuel when in closed loop