Hey guys hoping someone can point me in the right direction.
My partner has a TE that had the 3 litre in it the auto died so i bought a wrecked verada and put the 3.5 motor and auto from that into the TE im using the 3 litre ecu and the 3.5 is as it come from the other car no parts swaped the issue shes having is its only getting 370-390km to a tank highway or city driving doesnt make a difference.

The car seems to run ok a little ruff on idle but not real bad we got a new oxygen sensor that made 0 difference and on a long trip not long ago we were pulling a 8x5 trailer loaded and at night it was fine when day brake come the temp was creaping up so we had to run the heater to keep that in check no other time has it over heated im happy to accept that there not suited to towing just thought id add that in to cover everything.

The rear muffler on the verada was stuffed as in bent so we used the one that was on the TE issue here is its rusted pretty bad inside no holes in it but if you give it a kick it rattles pretty good like there are rust/metal flakes rattling around in there.

So is it that the rear muffler is part blocked causing reduced performance and there for using more fuel or should o look else were ? it has new plugs air filter and fuel filter

My partner took it to a mechinic recently and hes a big magna fan and he seems to think the muffler wont be the issue he thinks not using the 3.5's ecu is any thoughts on this and were we should look ?

The car has to make a Vic-Qld drive then last another 6 months or so then were getting a new car so dont wanna spend another cent on the car thats not needed as we have spent to much as is but if we can get another 70-150km a tank from it ill spend a few bucks

O2 sensor would be a good start. Not sure if the 3l and 3.5l ecu are compatible. I'm sure someone can clear that up.

02 sensor was done made 0 difference

I doubt that the 3.0 ECU would cause excessive fuel consumption under normal circumstances (in fact it could be slightly better than a 3.5 ECU consumption-wise), however if the coolant temperature sensor (not the sensor that feeds the gauge in the cluster, but the sensor that feeds the ECU) has failed, the ECU would be running the engine rich as if it never warmed up.

According to my Ellery workshop manual, the coolant temp sensor voltage should be less than 1V when the coolant is over 80degC (ie at full running temp), and will be over 3V when the temp is less than 0degC. This signal is on pin 83 of the V6 auto ECU.

Also, check your thermostat, sounds completely stupid, but the 6G72 and 74 run all 6 injectors all the time when the sensor for the ECU reads the coolant temperature as low, if shes not opening early enough, this could be the issue. It's a fairly simple check and can't hurt to try as of it is buggered, they're only 20-40 brand new. Put a brand new tridon hi-flow on my TS 6G72 and it made a noticeable difference to my fuel consumption.

hey guys thanks for that we had the fault codes checked nothing came up starting to think it may infact be that muffler

so as you do i bought a whole car for its exhaust haha