My UZ83's Fuel Ecconomy

[Cuzzo]

Hey,

Im getting shithouse economy from my 1uz powered mx83 grande auto. Stock ECU and everything *looks* working. No codes are being thrown.

I'm getting around 350 to a tank or premium.

What can be some of the causes of this?

Additional may or may not be related. When i do give it some stick i find a rev cut / some sort of limiter around 4-5k rpm. This is when it wants to change gears (auto) and it sits there for a second until i release the throttle slightly and let it change.

It doesn't have as much go as it should also. Down low its a bit sluggish potential cause its auto and potential cause its over-fueled.

I do need to pull the plugs and have a look but i haven yet. I'll try and get a video of my rev cut episode.

[-GT-]

First things first - stock ECU'd? Any codes? Oxy sensor not functioning/missing is my first guess - i get crap fuel economy as my oxy sensor is dead, ecu goes 'safe' and runs richer on low load, can't run closed loop cruise. Of course it's still an NA 4A so it's not breaking the bank, but i was getting about 10L/100km city driving.

Weird shifting behaviour is likely to be unrelated, but i know SFA about autos and can only say i remember other people having similar symptoms (ie won't shift until you lift a little) and it being rectified by adjusting ... a cable or similar relating to the shift point... yeah that's about all i remember, i zoned out after reading 'auto...'.

[RONA]

Limiter is 6krpm so thats fine. Mine will shift at WOT without hesitation.

How much is it taking to fill the tank for 350km. I get about 300-350km to half a tank in the LS400 which is around 45L during normal driving conditions.

Down low being sluggish is just due to 1uz needing to wind up a bit to get the big girl moving. They are a bit doughy until 2500rpm.

[Cuzzo]

around 65-72 dollar so that would mean around 65 L

[RONA]

around 65-72 dollar so that would mean around 65 L

You should be running 98ron, I can't remember paying less then $1.25/L except for tight arse tuesday for a while.

[The Witzl]

my UZS131 got around 400-450kms per 70-75L in city driving.

Sounds pretty normal to me, allowing for extra weight in your right foot.

[Aust162]

Doesnt sound right to me. my mates uzz30 soarer gets 500kms+ off a tank consistently..

[lexsmaz]

How long have you had the car & has it always been like this ?

I agree with GT i would suspect the oxy sensor first up, but it should have thrown up a code though ?

Are your diagnostics working ? as in do you get any codes at all out of the computer, from memory even if its all ok it flashs some sort of signal, bit rusty here as its been so long since i have looked ...

The shift points are not right as you said .. From memory my 1uz Mazda shifts at 7,200 WOT, but its been a while since i have driven it so i might be mistaken on that figure ... And as the other's have said they are a bit Doughy below 2,500 RPM, the Auto doesn't help this though ..

I would imagine economy should be around 12 and a bit per 100 km ..

[RONA]

The shift point is correct. I have a 1uz in a LS400 & the factory redline is 6000-6200rpm. Funnily enough that is also the limiter & where it'll shift with power mode on at WOT.

[Cuzzo]

Just to clarify it actually does this cut between 4-5k rpm.

Also ive only had the car for about 4 months now. Conversion was already done.

[onboost]

Hey mate,

Must be something wrong with it. I used to get 420 on e10 and 450 on pulp. It used to change gears at 6000.

[Bananaman]

How much of your driving is just 5min to work though? You're going to get shithouse economy if it never warms up...

[urantia]

Replace the coolant temp sensor if its old. Heaps of reports on this little sensor cusaing shit fuel economy and power.

Im getting right smack bang on 10l/100km's but i am doing mainly highway km's.

Ah here is the link about the coolant temp sensor - worth a read!

http://www.clublexus.com/forums/ls40...ange-pics.html

[lexsmaz]

Does the car run at a Normal operating temp ? Does the gauge move & work ok, in adding to urantia info if its not running to the correct working temp range as in to cold, the coolant temp sensor that he mentions will trigger more fuel to be dumped into the motor ..

[CrUZida]

Its probably not wired correctly (assuming all the sensors are working properly).

Check the coolant sensor against the MA70 TSRM
Replace the o2 sensors
Replace the plugs/leads/dizzys/rotors
Check the timing with it locked.
Check the voltage at the relevant ecu pins (to see if anything is miswired)

Failing that, take it to an EFI place.