High fuel consumption

BERNHARD M FISCHER

MEMBER
2004 KIA SORENTO
3.5L
V6
2WD
AUTOMATIC
213,000 MILES

Hi, after replacing several items (sparks, plug wire, water pump, A/C compressor, tappet gaskets etc.) They cleaned the throttle body from carbon. After that I experienced a very high petrol consumption (24l/100km). Doing a complete tuning they found several vacuum leaks at the manifold and throttle flap. Everything was done and the idle adjusted. No error codes, no engine light.
Now the consumption has gone down to 18/100, which is still to much. I noticed that after that repairs the rpm are going up to 3000 at normal acceleration. Also if I am driving with 2500 and take the foot from the accelerator the rpm are returning very slow to idle. It looks as it stuck at 1500, slowly going down to 1300, ending at 1100. Earlier the return to idle was instantly. Could this be the reason for the higher consumption? Could the reason be a sensor, if so which one? Thank you for your support and answer.
Bernhard
(additional Information, the car is always running with A/C as I am living in Sri Lanka. Therefore the consumption is a bit higher 16/100 I had before).

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

If the idle is returning that slowly and remaining that high then yes this will hurt your economy.

Sounds like you still have a vacuum leak. Can you put a vacuum gauge on the engine on a vacuum line and see what the gauge is doing?

Also, we may have an issue with the throttle relearn. Basically when you clean the throttle body the ECM has not learned the new position of the sensors so the idle is high. The issue with this is that I don't see a relearn process which normally means it is an auto relearn after you disconnect the battery.

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

Below is the info from the manual.

I would suggest checking for a vacuum leak with the gauge and then disconnect the battery for a few minutes to force the ECM to go through a relearn.

Let us know what you find with this.

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