Fuel average is poor! What can be the reason?

[zeeshanullah1999]

Salam Alaikum everyone, I own a Toyota Corolla 2005 SE Saloon (9th gen) with an automatic transmission. The car's mileage is 250K Kilometers. The issue I am facing is that the car gives me abysmal fuel mileage of around 6 kilometers per liter with AC on. Is this normal for this model? If not then what could be the cause of such poor mileage? The spark plugs were replaced recently, and the throttle body, sensors, and fuel line were cleaned, yet the fuel average is still so poor.

[pwuser152534163546]

I had it for pretty long time infact had 2004 and 2005 they were best for cng i removed cng in both and i used to get 8km/l in karachi with moderate traffic. It never improved

[zeeshanullah1999]

8km/l was the maximum that you were getting right?

[dayrider]

What city are you in? What route is it used on? Is the engine original?
These did 10 to 12

[pwuser162557941033]

I owned one of these with similar mileage. It netted around the same. 5.5-6.5 Km/L.

Investigating this and improving mileage is beyond the scope of the average local mechanic. You will have to be very thorough with your monitoring and logging of parameters in order to see which ones are abnormal and why.

Throttle body doesn't need to be cleaned under most circumstances. It's a popular money grab here.

Spark plug replacement won't do anything unless your existing spark plugs were at the end of their life.

How was the fuel line cleaned? To check whether or not any fuel line obstructions or dirt were causing lowered performance, you would have to compare the fuel pressure before and after the process.

[pwuser152534163546]

Yes 8 was max in city never tried long route karachi traffic is quite heavy in the evening on main roads

[Moderator]

@Kamran.Aslam Corolla with poor fuel average, whats your catch on this

[msabbasi]

250K km is a pretty high milage. Could it be that the exhaust system is chocked up with carbon? I guess during the lifetime of the car it must have had the rear muffler replaced but what about the one right next to engine? It a long shot. If it was my car, I'd sniff the exhaust for rich mixture (I am old school). The right way is to use an exhaust gas analyzer. Also I'd check if the cold start fuel enrichment function cuts out once the car reaches operating temperature. You might need a good OBD analyzer and look at live data such as fuel trims etc. These are just a thought off the top of my head. .

[pwuser162557941033]

If it was my car, I'd sniff the exhaust for rich mixture

Yes mine does smell rich. I'd do the same. Log OBD2 fuel trim, fuel pressure, AFR, etc. I'd love to find someone who has an exhaust gas analyzer in Karachi.

[zeeshanullah1999]

I am in Karachi, and yes the engine is original. The car is used within the city for daily errands. Could it be a timing belt issue? Since there is a ticking sound when I suddenly accelerate and the mechanic has said that it is a timing belt issue, could the timing belt affect the economy adversely ?

[zeeshanullah1999]

So were you able to get to the root cause of your car's poor fuel average?

[zeeshanullah1999]

I hope Kamran sb is able to help

[dayrider]

Get the timing belt replaced asap. If it snaps, your engine will go kaput. And no, that has nothing to do with fuel consumption.
Get a new fuel pump, and replace fuel filter. That should help

[pwuser162557941033]

My SE Saloon had a 1.6 3ZZ-FE. That is a timing chain drive engine. As a rule, I avoid mechanics who, using their 32-bit 96KHz lossless ears, attribute a sound to "timing belt" in a timing chain engine. The same happened with me when a mechanic confidently puffed their chest and said it was timing chain noise on my Suzuki belt-drive engine. "Pura injun kholna parayga" 🤦‍♂️

Do not purchase parts or replace parts without doing a proper diagnosis. No random speculation will help you solve the problem.