High fuel consumption

Tiny
MBIWE OBUM VAL
  • MEMBER
  • 2000 TOYOTA 4RUNNER
  • 3.4L
  • V6
  • 4WD
  • AUTOMATIC
  • 206,789 MILES
The fuel consumption of my car has been high in recent time and I have changed the airflow meter as advised by my mechanic but problem persist.

Would need your advice on this as it is giving me sleepless night. I just checked the mileage on the meter board now and it reads 206,738, as at the time of filing this report.
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Saturday, November 17th, 2018 AT 9:21 AM

15 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi and thanks for using 2CarPros.

High fuel consumption can be the result of many things. Simple things such as a plugged air filter can cause it. Also, with this many miles, compression may be getting lower and requiring more fuel to produce the same power as before.

I have to start with a couple questions. First, when was the vehicle last tuned up? Also, how is the vehicle running? Is the check engine light staying on when driving? Has there been any work done to the vehicle recently? Has there been any brake work done recently?

If I had the vehicle, I would first start with the simple things I mentioned. If they were all good, it starts becoming a bit more complicated. I would check what is called fuel trims to see if the engine is running rich. Also, I would check and confirm the engine coolant temperature sensor was working properly. If it tells the computer it is much colder than it actually is, the computer will make the air/fuel mixture much richer. Thus, it will use more gas.

Let me know any details you can think of. If you have a live data scanner, let me know that, too.

Take care,
Joe
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Saturday, November 17th, 2018 AT 6:18 PM
Tiny
MBIWE OBUM VAL
  • MEMBER
Good evening, I just had tune up of my car but the. Fuel consumption increased after servicing the injector nozzles and the most surprising is the early morning black smoke from the exhaust pipe.

Also having black carbon around the exhaust pipe which wasn't there before now, I would be revisiting the mechanic shop tomorrow.

I refuel my car every two days with about 33 liters and it is getting frustrating, I need urgent help.
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Wednesday, December 26th, 2018 AT 9:59 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome back:
Since you see black smoke, that tells me the system is running rich (too much fuel). I suggest checking fuel pump pressure. If the regulator isn't working properly, too much pressure will build and it will decrease mileage.

Here is a link that shows how it is done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Here are the directions specific to your vehicle. The attached pictures correlate with these directions.

_____________________

FUEL PUMP

ON-VEHICLE INSPECTION

1. CHECK FUEL PUMP OPERATION

a. Connect a TOYOTA hand-held tester to the DLC3.
b. Turn the ignition switch ON and push TOYOTA hand-held tester main switch ON.

NOTE: Do not start the engine.

c. Select the ACTIVE TEST mode on the TOYOTA hand-held tester.
d. Please refer to the TOYOTA hand-held tester operator's manual for further details.

e. If you have no TOYOTA hand-held tester, connect the positive (+) and negative (-) leads from the battery to the fuel pump connector.

f. Check that there is pressure in the fuel inlet hose from the fuel filter.

HINT: If there is fuel pressure, you will hear the sound of fuel flowing. If there is no pressure, check the H-fuse, M-fuses, fuses, EFI main relay, circuit opening relay, fuel pump, ECM and wiring connections.

g. Turn the ignition switch OFF.
h. Disconnect the TOYOTA hand-held tester from the DLC3.

2. CHECK FUEL PRESSURE
a. Check the battery positive voltage is above 12 V.
b. Disconnect the negative (-) terminal cable from the battery.
c. Remove the 6 bolts, and disconnect the No.2 timing belt cover.

d. Remove the union bolt holding the fuel pipe to the delivery pipe and gasket.

CAUTION:
- Put a shop towel under the delivery pipe.
- Slowly loosen the union bolt.

e. Install SST (pressure gauge) to the delivery pipe with the 2 gaskets and SST (union and union bolt).
SST 09268-45014

Torque: 34.3 Nm (350 kg.cm, 25 ft.lb)

f. Wipe off any splattered gasoline.
g. Connect a TOYOTA hand-held tester to the DLC3. (See step 1)
h. Reconnect the negative (-) terminal cable to the battery.
i. Turn the ignition switch ON.
j. Measure the fuel pressure.

Fuel pressure: 265 - 304 kPa (2.7 - 3.1 kg/Sq.cm 538 - 44 psi)

If pressure is high, replace the fuel pressure regulator. If pressure is low, check the fuel hoses, fuel hose connections, fuel pump, fuel filter, fuel pressure regulator and VSV for the fuel pressure control.

k. Disconnect the TOYOTA hand-held tester from the DLC3.
l. Reinstall the No.2 timing belt cover with the 6 bolts.

Torque: 9 Nm (90 kg.cm, 80 in.lb)

m. Start the engine.

n. Disconnect the vacuum sensing hose from the fuel pressure regulator, and plug the hose end.
o. Measure the fuel pressure at idle.

Fuel pressure: 265 - 304 kPa (2.7 - 3.1 kg/Sq.cm, 38 - 44 psi)

p. Reconnect the vacuum sensing hose to the fuel pressure regulator.
q. Measure the fuel pressure at idle.

Fuel pressure: 226 - 265 kPa (2.3 - 2.7 kg/Sq.cm, 33 - 38 psi)

If pressure is not as specified, check the vacuum sensing hose and fuel pressure regulator.

r. Stop the engine.
s. Check that the fuel pressure remains as specified for 5 minutes after the engine has stopped.

Fuel pressure: 147 kPa (1.5 kg/Sq.cm, 21 psi) or more

If pressure is not as specified, check the fuel pump, pressure regulator and/or injectors.

t. After checking fuel pressure, disconnect the negative (-) terminal cable from the battery and carefully remove the SST to prevent gasoline from splashing.
SST 09268-45012
u. Remove the other union bolt, 3 gaskets and fuel pipe from the delivery pipes.
v. Reinstall the fuel pipe with 4 new gaskets and the 2 union bolts.

Torque: 34.3 Nm (350 kg.cm, 25 ft.lb)

w. Reconnect the negative (-) terminal cable to the battery.
x. Check for fuel leaks.

3. INSPECT FUEL PUMP RESISTANCE
Using an ohmmeter, measure the resistance between terminals 4 and 5.

Resistance: 0.2 - 0.3 Ohms at 20 C (68 F)

If the resistance is not specified, replace the fuel pump and/or set plate.

4. INSPECT FUEL PUMP OPERATION
Connect the positive (+) lead from the battery to terminal 4 of the connector, and the negative (-) lead to terminal 5. Check that the fuel pump operations.

NOTE:
- These tests must be done quickly (within 10 seconds) to prevent the coil from burning out.
- Keep the fuel pump as far away from the battery as possible.
- Always do switching at the battery side.

If operation is as not specified, replace the fuel pump and/or set plate.

Let me know what you find

Joe
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Wednesday, December 26th, 2018 AT 6:35 PM
Tiny
MBIWE OBUM VAL
  • MEMBER
Thanks for your timely response. I am headed to my auto mechanic now. The plugs where change three weeks ago, while the nozzles were serviced and other routine acquaintance, but my car wasn't having this early morning smoke.
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Thursday, December 27th, 2018 AT 2:18 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Either there is an injector or injectors leaking or the fuel pressure is too high. Let me know what you find out.

Take care,
Joe
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Thursday, December 27th, 2018 AT 2:50 PM
Tiny
MBIWE OBUM VAL
  • MEMBER
Thanks once again, my vehicle was scanned and was discovered that one of the oxygen sensor was bad and both were changed.

Though a thick smoke came out initially when the engine was turned on and idling but when accelerated the black smoke continued which was unusual though but I was told it would clear out and the check engine light automatically went off on its own accorded after both oxygen sensors were replaced.

I would be tested driving today to check on consumption rate and other signs.

When the sensor was brought out it was covered with black and heavy carbon.
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Thursday, December 27th, 2018 AT 8:45 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome back

That can do it because the computer determines fuel / air mixture by information from the sensors. Let me know if that takes care of the problem.

Happy new year and safe roads ahead.

Take care,
Joe
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Thursday, December 27th, 2018 AT 9:23 PM
Tiny
MBIWE OBUM VAL
  • MEMBER
Good morning, was on a road test and the check engine light came on again, though still observing the fuel consumption level.
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Thursday, December 27th, 2018 AT 11:42 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
What code is showing when the computer is scanned?
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Friday, December 28th, 2018 AT 7:41 PM
Tiny
MBIWE OBUM VAL
  • MEMBER
The fuel consumption has reduced drastically but the check engine light is still on.

Can remember what was displayed on the scanner.
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Saturday, December 29th, 2018 AT 2:03 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome back:
That's good news but I question why the light is back on. If you have the chance, have it scanned and let me know what you find.

Joe
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Saturday, December 29th, 2018 AT 7:01 PM
Tiny
MBIWE OBUM VAL
  • MEMBER
I woulde surely do that, I am at the countryside now which is about eight hours drive to the city.

I also observed that when I am in traffic and I step on the brake pedal, the engine jerks like a plug malfunction but I just changed the plugs during the last servicing/tuneup.
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Sunday, December 30th, 2018 AT 12:01 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi and welcome back:

I wonder if you have a vacuum leak to the brake booster. Check to see if there are any leaks to the vacuum booster behind the master cylinder.

Here is a link that shows how that is done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know what you find.

Joe
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Sunday, December 30th, 2018 AT 2:33 PM
Tiny
MBIWE OBUM VAL
  • MEMBER
Sorry I forgot to add that, when the engine is idling in traffic it jerks also, that's when the gear is disengaged.
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Monday, December 31st, 2018 AT 12:21 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Then it does sound like a misfire. What is the new code? Is it related to a misfire? If possible, let me know the code.

If I don't hear from you tonight, I wish you a happy new year!

Take care,
Joe
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Monday, December 31st, 2018 AT 2:57 PM

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