Bad fuel economy

[redtrouble_]

I have a 4g15 sohc (fuel injected) in my libero I'm getting about 250km per tank, I don't drive aggressive nor in heavy traffic and I use A.C moderately. Also when accelerating I get some heavy heavy black smoke.
Things I've checked:
- MAF
- Fuel pressure regulator
- I checked for vacuum leaks

I also recently added a fuel injector cleaner to the gas tank.

I'm really don't know what's the issue, I'm no expert just a DIY guy

[skylinechild]

I have a 4g15 sohc (fuel injected) in my libero I'm getting about 250km per tank, I don't drive aggressive nor in heavy traffic and I use A.C moderately. Also when accelerating I get some heavy heavy black smoke.
Things I've checked:
- MAF
- Fuel pressure regulator
- I checked for vacuum leaks

I also recently added a fuel injector cleaner to the gas tank.

I'm really don't know what's the issue, I'm no expert just a DIY guy

carry the car to do a full EFi tune up. ( full efi tune up should consist the cleaning of fuel rail and injectors throttle body and intake manifold valve & air flow sensor )

check ryotech performance ( google him) or Big Z on the forums ( search his name on tuner) both are more than qualified to service your car

things to carry with you:
1. new air filter
2.new fuel filter
3. spark plugs
4. oil and oil filter ( its best to let the tune up coincide with ur regular oil changes some carbon thats dislodged from the system is deposited into ur engine oil)

ryotech is located in claxton bay
big z is located in princes towne.

[adnj]

I have a 4g15 sohc (fuel injected) in my libero I'm getting about 250km per tank, I don't drive aggressive nor in heavy traffic and I use A.C moderately. Also when accelerating I get some heavy heavy black smoke.
Things I've checked:
- MAF
- Fuel pressure regulator
- I checked for vacuum leaks

I also recently added a fuel injector cleaner to the gas tank.

I'm really don't know what's the issue, I'm no expert just a DIY guy

The biggest contributors to poor fuel consumption in EFI engines are typically bad spark plugs, blocked air filters and faulty O2 sensors.

Black smoke is a rich mixture.

You are getting about 4km/l and I would guess that 6 to 8km/l would be closer to what it should be. I would also look at the ignition system for misfires or cold sparks (orange instead of blue).

[Dave]

Were the valves ever adjusted? What color are the plugs? Is it black smoking? Is it burning oil and what body are you using? Was the resistance on the wires ever checked? What wires are being used? Were the pcvs ever checked? On an engine that old, these should be checked even before an efi clean is done.

[redtrouble_]

Were the valves ever adjusted? What color are the plugs? Is it black smoking? Is it burning oil and what body are you using? Was the resistance on the wires ever checked? What wires are being used? Were the pcvs ever checked? On an engine that old, these should be checked even before an efi clean is done.

PCV valve was changed recently and no it doesn't burn oil. I use 10w40 oil

[kamakazi]

Normally for a fuel injected vehicle to have poor fuel economy you look at items controlling the fuel as you you have initially done. An observation of black smoke usually indicates a vehicle running a rich air fuel mixture.
This could mean a bad o2 sensor as you already stated checking the maf.

As a DIYer I suggest tackling some of the easier stuff first though
Spark plugs (either replace or clean the contacts and gap them; can get a replacement set of 4 for about $100). When you take them out, visually inspect and compare them to charts that they have online letting you know if your your plugs are fouled or damaged. (Never heard of a hot or cold spark, only of hot and cold spark plugs)

Clean the distributor cap and rotor contacts.

The oil viscosity is fine
Tank added Fuel injector cleaners in my opinion don't really work well at cleaning... Better for maintenance maybe

Amsoil power foam is your friend here. Now personally I have never removed injectors to clean them for fear of damaging seals... But it is an option. I usually spray a little foam into my low gas tank and let it cycle like that (it reverts to a liquid after a while). Do not spray this stuff with the engine running to do an intake clean... That is a whole other problem that you will create doing that.

Unless the air filter needs changing don't bother changing it... And don't use any reusable filters... They are a waste of time and money... Just my opinion