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Discussion Starter · #1 ·
I remember when I first got my 99 Excel (accent) to some, I'd probably gather around 500km a tank around town driving. 700km + on a freeway.

Now it seems im struggling to get 400km on the freeway. Its hot up here compared to where i use to live, so the air con, even though it doesnt really work past fan speed two - is on for most of the drive - surely the ac wouldnt chew that much more fuel?

I like to think I have a bit of car knowledge, so i think ive looked into things like tyre pressure, oxygen sensors etc.
The car has a K&N air filter that is cleaned and re oiled every service. (7.5k km)


Is there anything I could be look at in the face thats escaping me? Fresh fuel filter, and also replaced the fuel pump as i have a doner car - to no effect.
 

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fuel economy is a fickle thing...one tank of gas to another can make a difference of over 100km on that tank.

first step, are you tracking your tank level vs mileage with the gauge or at the pump? the fuel sender could be inaccurate now. the using the pump and knowing the tank volume could verify this.

the heat (in theory) can make a difference. the A/C can as well, but i don't buy going from 700km + down to around 400km. one thought there is check your belts. a loose belt can slip wasting energy.

there's other issues to check. first, forget the fueling system for the most part. the filter and the pump won't help anything. you've got the air filter covered by the sounds of things. check for anything stuck in the intake piping that shouldn't be.

spark plugs and wires can cause this if not changed in a long time. it'll be pretty obvious once you get them out :)

get a code scanner on it, not sure about what the OBD standards were in Oz for 1998, but it might give you a clue...

check the wheels for a dragging brake caliper. see the wheels turn freely when in neutral and the car jacked up.

finally, considering its an older car, it may be worthwhile to check the engine compression. if you can change spark plugs and pull a relay, you can check engine compression. the compression tester is not an expensive tool. you might find that the engine is getting old now and rings are wearing or possibly a valve is not sealing right anymore. i don't know the vehicle's history or mileage so this is just another possibility.

check all the vacuum lines as well...cracked or broken like can cause problems. not usually this much, but i'm not overly familiar with what your excels are like in Oz.

some would say use fuel injector cleaner....up to you, but i am not a fan of the stuff. my accent has almost 260k kms on it and never once used any cleaners in it....because its already in the fuel at the pump. i'm more a fan of taking the injectors out and cleaning them properly weather it be by reverse flow cleaning or ultrasonic. to each their own. but in short, yeah a badly clogged injector can cause problems. the fuel is supposed to be misted into the intake. if its close, you're usually fine. if its coming out as a stream well you might have a problem :p

the last thing is take any unnecessary weight out of the car.
 

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the last thing is take any unnecessary weight out of the car.
This would include the wife or girlfriend, too, yes? Unless she's in the trunk for added traction in the snow.
 

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Another thought is if you're comparing 1999 to now you may be using more ethanol gas than you did 14 years ago which will also reduce MPG.
 

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Discussion Starter · #5 ·
thanks for the reply guys

zero gravity - thanks for going so in depth.

I have had the air intake off and on, sprayed carby cleaner through the whole intake, which helped the idle a little bit when left over night, but it does seem to take a while to idle down and has had since i got it. Have run plenty of carby cleaners and octane boosters through it over the time ive had it, and replaced the belts - except the timing, which i have, but havent had a chance to put it on yet.

car was actually bought off my ex gf who's grandmother drove it before that - it was very low km, and i guess not the greatest maintained - in terms of the mechanic ripping off an elderly woman as they do. when i got it, i was getting near 500km a tank city driving.
Have recently had new tires put on it (before posting the thread) and wheel allignment.
I did buy an OBD II scanner, but its not compatible with the car - have to get an obd one which are harder to find.

as far as vacuum lines go, the only one I am suss on is from the fuel pressure regulator to the intake. the FPR has been leaking a bit of oily looking fuel under it for a while, but i ended up undoing that and re seating it and seems to have sealed it.

if i was to take the carby/throttle body off to inpect how dirty it is, would i need some sealant again or will the gaskets take back up?
Im in a rural area now, so parts/gaskets are harder to come by than when i was in the city.

i have somewhat tested the volume of fuel on long distance trips, it seems pretty accurate. this is with all different types of fuels - they have phased out ethanol 91 up here, so i get regular 91 ron, 95ron and 98. the same economy not matter what the fuel is.

i am just stumped that my poor old car cant do what it use to.

thanks again, appreciate it.
 

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Have run plenty of carby cleaners and octane boosters through it over the time ive had it, and replaced the belts - except the timing, which i have, but havent had a chance to put it on yet.
the cleaners/octane boosters are actually a terrible idea. there's really no evidence that they do anything and its entirely possible that they could cause damage in the long run. octane boosters usually raise the octane by 1 point or less. its not worth your money.

also, the fuel you're buying likely already has plenty of cleaners in it...cleaners that are tested and known to work fine with your fuel. the other stuff who knows?

my accent has nearly 260,000kms on it currently and i have never once run any cleaner in it. i haven't needed to either. troubleshoot problems and fix them, don't waste time and money on snake oil.

you will want to do that timing belt. its an interference engine so the consequences of the belt snapping can potentially be destroying the engine.


if i was to take the carby/throttle body off to inpect how dirty it is, would i need some sealant again or will the gaskets take back up?
Im in a rural area now, so parts/gaskets are harder to come by than when i was in the city.
if you're careful, that gasket is usually reusable just fine. if its stuck to either the manifold or the TB, just don't peel it off or anything that would risk tearing it.

if you do tear it, don't sweat it. there are a few options without getting a new gasket. one is to get a tube of RTV silicone. you can use it to reenforce the old gasket or even replace it entirely. works great. another option is to buy a couple sheets of gasket material and cut your own with a razor. use the old gasket or the TB itself for a pattern to cut.

i have somewhat tested the volume of fuel on long distance trips, it seems pretty accurate. this is with all different types of fuels - they have phased out ethanol 91 up here, so i get regular 91 ron, 95ron and 98. the same economy not matter what the fuel is.
while we're on the topic, let's talk about octane and what it means. first and foremost, higher octane does NOT mean higher energy content in the fuel or higher gas mileage in any way. forget nonsense of a 'more complete' burn or anything like that. octane is the fuel's resistance to detonation, or the fuel burning all at once when its ignited. the ideal scenario is a flame wave starting at the plug and moving towards the piston to push it down. detonation is very dangerous to the combustion chamber and can trash an engine in no time.

that being said, your car is designed to run on 'low' octane fuel just fine. higher octane is used for fun stuff like turbocharged cars and even cars that use very high spark advance. for example, some hondas will do this. put higher octane in and the spark is advanced (fires before cylinder reaches top in compression stroke) yielding a bit more power. your accent is nowhere near advanced enough to do that :p

what will make a difference is the ethanol. ethanol has a lower energy content...that will translate directly to less fuel economy. it really is as simple as energy in = energy out - losses.

all you can really do is troubleshooting. a significant drop in fuel economy indicates a problem somewhere....might be as simple as the engine compression has dropped as the rings wear over time. that will cause the problem easily. that's why i suggested to check the compression ;) if its low, you got a big job ahead of you if you want to fix that.
 

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Discussion Starter · #7 ·
thanks for the info zero.
I had no idea about that octane stuff, so thats good to know. ive usually just tried different fuels in different cars and the 98 usually has a better economy. thats on a commodore over here which uses a gm buick engine i believe? and a few other cars this has worked on.

I did post a few months back about a fuel leak, still couldnt find it under the car or in the fuel lines anywhere. just smells of fuel in the cabin on a hot day. thats when i replaced the pump and filter, I sussed out all the connections and seals. all seemed ok.

Possible that a small leak could lead to a drop in economy? I think so. But I cannot find it.

Thanks again for the info. If I'm feeling adventurous, I might have a look under the carby. It did have alot of black sooty stuff in there when using the cleaner, its possible if dislodged something and its gone into a jet. thats if they even have jets on these cars? lol. Cars ive worked on the most have been the old carby carby cars.
 

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higher octane only has an effect on fuel economy under two conditions:

- the engine is able to take advantage of the higher octane rating and changes the timing/spark advance to give you a little bit better thermal efficiency. some honda engines do this.

- the regular fuel has ethanol in it and the premium does not. usually regular has 10% ethanol and depending on where you live and where you buy your fuel, sometimes premium does not. gasoline has a higher energy content than ethanol. its not usually worth the cost though as the boost is quite minimal...as always your mileage may vary...haha pun.

as always, don't go replacing parts at random. waste of time and money, unless you don't want either. you're welcome to send some cash my way. i accept all currencies.

when hunting down a fuel leak your nose is the way to go. look for any wetness along the whole system. another thought is the charcoal filter for the EVAP system may be saturated and trashed....hold the vapours and will eventually vent them off. very common with these cars.

that is if your car is so equipped with such a system....can't say i have ever seen a carb'd accent :p
 

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the regular fuel has ethanol in it and the premium does not. usually regular has 10% ethanol and depending on where you live and where you buy your fuel, sometimes premium does not. gasoline has a higher energy content than ethanol.
Best to go to pure-gas.org to find addresses, details & a great zoomable map for 100% gasoline. Ethanol in gasoline can be, or not be in any octane. Not only does 10% ethanol blend have less btus of energy than 100% gasoline, ethanol needs high compression ratio (16:1) ethanol engines to obtain its energy output. That is why low compression ratio(9:1 to 11:1) gasoline engines have 8% to 5% better mpg than 10% ethanol blends give.
 
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