"Max Out" Negative Fuel Trim

Posts specific to the 2.0 litre Turbo engine

"Max Out" Negative Fuel Trim

Postby LeokzzZ » Tue Jun 04, 2019 2:36 pm

Hello all!

So I'm finally got my OBDII adaptor right and able to read all my ECU specs.
I was previously experience a horrible fuel economy and can get a heavily smell of gasoline when idle.
And not long ago my Winston(yeah that's what i call my lil lib) started to hesitated when accelerating as well as jerking(happened with the hesitation together all the time, when set off from the traffic light, press the throttle there is no power and accelerated very rough and slow, then suddenly the power kicks in a bit more, and then a bit more, and then feels like full power, and then i hit the speed limit) and rough idle, even stalled once.
So yesterday i got the OBD and read, found the fuel trims are both negative at idle(lower than -15 to -25%), LTFT hits the minimum basically all the time and the STFT stayed in negative too, sometime under accelerating the fuel trims are still negative. And i believe these are not normal. I thought it was the MAF so I cleaned the MAF and the Intake Filter but it doesn't affect the Negative Fuel Trim at all. I don't know if it's normal or what but at idle the MAF G/S reads around 3.8-4.2 g/s and the voltages are around 1.3-1.4V at idle.

I was still doubting if it's the MAF's problem, otherwise i think it should be the Fuel injectors' problems or Fuel Pressure Regulator?

Thank you all very much for helping Winton in advanced!!
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Re: "Max Out" Negative Fuel Trim

Postby norbs » Wed Jun 05, 2019 5:42 pm

G'day.

MAF voltage at 1.3 to 1.4 at idle is too high. Should be 1.2 to 1.6.

I had a similar problem to you. Did the usual checks for leaks, cleaned maf etc..

In the end it was a dodgy MAF plug/wire. I found it by jiggling the wire whilst watching the fuel correction. It also effected the idle when I jiggled it. I got on to Rising Sun in QLD who snipped me a plug (including 30cm of wiring) from a wreck. Cut off existing at around 20cm from plug and soldered in replacement (used heat shrink and tape etc.). After that she ran perfect with rock sold MAF voltages.
'05 Lib GT with a few mods :-)
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Re: "Max Out" Negative Fuel Trim

Postby LeokzzZ » Wed Jun 05, 2019 7:37 pm

Yeah i was doubting the same thing, and I just changed another MAF and the car stop hesitate or jerking when press the throttle but the fuel trim is still negative but a lot better than before.
But I doubt if is the wire which become a little bitch, it will still affect the throttle response, so let's see.
Thank you very much
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Re: "Max Out" Negative Fuel Trim

Postby bigBADbenny » Fri Jan 10, 2020 8:41 am

How’d you go with fixing this?
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