Poor mileage

[Ho Siam Yong]

Hi there,
I am begging for all your help as I have been trying to solve this promblem but to no avail.

My car is a 92 Corolla 1.6L SEG AE101 with 4AFE engine,223000km(similar to a US 93 Corolla but without oxygen sensor)

It all started 1.5 year ago when my mileage started to degrade from 420Km per 40litre to 300km per 40 litre.It once drop to 200Km per 40litre but after replacing the rear wheel bearings it got back to the 300km/40l standard.There is no abnormal sound in the boot and idle/running just fine as per normal.

I had sent it to the Toyota agent to have the engine tune up but the condition had not been improved.I later sent to another workshop for repair and the mechanic had advanced my timing to give more power to the vehicle and again the fuel mileage is neither improve nor degrade.Recently,I had the engine tuned again by the Toyota and after changing parts that I could think of(mostly getting ideas thru' reading the valueable threads that you guys had posted here).Thing never get better or worst.

Parts replaced so far for the past 12 months:
(1)Engine oil(Mobil one);
(2)Air filter;
(3)Spark plug;
(4)Spark cables(NGK power cables);
(5)Cap and rotor;
(6)Rear wheel bearings;
(7)Clean throttle body;
(8)tires(all 4 of them) and wheel alignment;
(9)Auto trans fluid replaced.

[Raddman]

At that millage it might be time for an engine rebuild, rings, valves etc. etc, did you ever have a cylinder pressure check done?...Raddman

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"HONK IF ANY PARTS FALL OFF"

[boosted gt]

that engine is just getting broken in

[Jonchilds]

What kind of driving do you mainly do?
The only thing that I can really think of is that you've got some poor quality fuel, as in my 1993 'EB' Ford Falcon (Australian 4.0L) I'd see atleast a 15% change in fuel consumption by going from 91 to 95 octane. I've yet to try this in the corolla, but its definately noticable in the larger engines.

Have you had the injectors out to see if they're getting dirty? Also if the car has a manifold air flow sensor, see what condition that is in.

[Ho Siam Yong]

Thank you very very much for the inputs.

I am actually not familiar with the engine things.I am unaware of the cylinder pressure I guess when I sent my car to the Toyota,they ought to have it checked but at the end they suggested me to have my exhaust pipe(and cat) replaced,which I did and yielded no result.

My wife is driving the car most of the time and the rpm is kept below 2500.I had been switching from Shell V-power to Caltex and not a different felt.I had been using the injector cleaner from STP every 4 months and I was wonder if that help?This Corolla doesn't have the air flow sensor but I think there is a inlet air temperature sensor in the filter box.

I am terribly sorry as I had missed out an important thing.The 300km/40l mileage is based on 100% city drive.When come to highway,it can hit 550km/40litre.

[Jonchilds]

You're getting 7.2L/100km on the highway? Thats what I get with a mix of 50/50 City/Highway, and I'm not really a gently driver to these smaller cars (or any car). Maybe you might need to get the computer's EFI values remapped.

My AE92's just shy of 300,000km and AFAIK it hasnt had a major overhaul or anything to the engine though its just had a new clutch, and it needs something done with the steering.

[Flashmn]

You're getting 7.2L/100km on the highway?

I'd be happy to get 7.2L/100km on the highway.. I get closer to 10l/100km ;P

[TOcorolla]

7.2l/100km is pretty good.
i usually get between 8-9L/100km