VT commodore surging like fuel starvation

[kevo91]

okay so i have a VT commodore, it runs gas and fuel, I've ran on gas for awhile alternating between both the gas system went bam, So ive been running on fuel and it seems too serge when i take of i travel about 140km aday in travel for work.
so anyways when i travel at 100kph between 1500-2000 revs now when im at this range i will put pressure on the trottle too keep the speed an what will happen is it feels like it surges and makes the car completly shutter an it will gain no revs an no speed now it idels rough aswell, sometimes when i take off it has no power an the rev go up an down like crazy "like a blockage" not enough fuel getting through now im not sure if the fuel pump is going or fuel filter is done

Not sure.
please help

also when it ran on gas never missed a beat didnt have this problem so it makes me think its not the leads or plugs that are bad

 

[Tree cutter]

If it backfired while running on gas, it will probably have a hose blown off or split between the throttle body and air flow meter. if this has happened then your air flow meter will not work properly so your car will run lean.

 

[chriso-k]

I'd like to hook up to your ECU and look at the car's STFT & LTFT along with O2S and MAF graph info, at the speed range you've indicated. Only way to come up with educated answers.

 

[VTowner025]

My car has the exact same thing, getting it looked at tomorrow, just out of curiosity what is a STFT and LTFT?

 

[accentstencil]

My car has the exact same thing, getting it looked at tomorrow, just out of curiosity what is a STFT and LTFT?

I'm guessing Short Term Fuel Trim and Long Term Fuel Trim.

 

[VTowner025]

I'm guessing Short Term Fuel Trim and Long Term Fuel Trim.

Thanks, learn something new everyday.

 

[VTowner025]

Good website link here, that seems to explain it in good detail: Fuel trim can be a valuable diagnostic tool - Eastern Manufacturing

 

[EYY]

It'll be a vacuum leak. Check the hoses underneath the throttle body and at the back of the plenum

Replace your coils, plugs and leads too. If it backfired when running on lpg, it's because the ignition system isn't up to scratch, or it's running too lean.

 

[devilly]

mmmm,me thinking if you car runs fine on lpg ,every other week you should be running petrol,have seen petrol that's dark purple nearly black before, would check to see if you have fuel contamination,which would lead to blocked fuel filter and blocked injectors,may have to flush the petrol and put in fuel injector cleaner and see how it goes....