Engine swap now high fuel consumption

[Gus The Snail]

Hey all..

Just swapped out my near 400,000km ecotec for a 124,000km one , swapped over a few sensors , but have found after a good highway run im losing about 150km per tank. I maxxed out at 721km from the old motor , now im lucky to get 600km on the exact same drive.. It does feel like it wants to stall out sometimes when taking off or the AC compressor kicks in. Still drives like normal , but does seem a little under powered compared to the old engine ( replaced as it developed a rattle somewhere - havent pulled it down yet ).

Any thoughts as to why my economy went to crap?

 

[VK SL 3800]

Could be a fuel pressure problem, also if your new engine is a VT onwards the injectors are slightly different if you didnt change them to the VS ones.

 

[EYY]

It's often a problem when you either haven't plugged in the o2 sensors, or they have a poor earth (make sure you check all earths - I think there's one on the rear of the passengers head and the front of the drivers head near the tensioner.

Before you do anything drastic, make sure you check for fault codes. If it's using that much fuel, it'll almost certainly have a fault code set. Does the engine light come on at all when driving?

 

[Gus The Snail]

No engine light or fault codes. I might try the injector swap out with the original ones and see if that makes a difference.

All earths are connected.

 

[Immortality]

Not just the injectors but the rails and FPR too. VS ecotec runs 3bar fuel pressure VT, onward use 3.5bar. Better yet, use the later style injectors as they are better than the VS ones but have it tuned to suit.

It wanting to stall sounds like an IAC problem. Clean the TB to fix ( most likely).

 

[Gus The Snail]

Engine was a series 3 VS. I have the original computer that came with the engine and harness.. should i swap computers and see if that makes a difference?

 

[Immortality]

Not sure TBH.

I'd also check the plugs/leads on the new(er) engine, they might be really old and crappy causing your fuel usage issue.

 

[Gus The Snail]

plugs , leads coils were all from the original engine

 

[VK SL 3800]

Somewhere the VS utes got the VT engines fitted factory, id be leaning towards the Injectors to start with.