Dire Fuel Consumption

[dibber]

Hi,

My 98 1.8 Avensis has been utterly dire on fuel consuption since I got it a few months back. I reckon around town I am getting, if I am lucky, 25mpg.

The car runs ok but feels a bit flat, though having not driven another one this may be the way they feel to drive?

I serviced the car the other day with new plugs, oil and filter and new air filter and it has made no difference.

When the car is pushed fairly hard the cat stinks on it, so much so it gets into the cabin and almost makes it impossible to drive the smell is so intense. I checked the cat to see if it had had a new one recently but it looks to have been on for a while. I had 15 yrs in the Motor Trade as a mechanic but have gotten out of touch with things so any pointers would be appreciated.

Any suggestions or has anyone had a similar experience?

[TRIGGER]

Hi m8, i havent got a clue why your fuel consumption is so high, but the smell i get aswell, I have a w plate 2000 1.8gls with only 30000 on it and the cat smells when pushing it hard and when i start it up first thing in the morning, got it an mot emissions test thingy and the cat and all other readings came out normal, also got a garage to check the cat and they said it was k aswell. I would take the car for the emissions test to make sure the cat/lamba sensor etc is k, hope this helped you out a little m8, kind regards TRIG:].

[purvesh81]

I had similar problems, and my local dealers reported the secondary valve throttle valve on the inlet manifold was stuck.

You could have a similar problem.

[rf76]

'Ow do, Fella!

I too own a '98 Avensis with the 7A-FE engine. If yours is the same, have a look at the vacuum rod on the end of the inlet manifold (cambelt side) to see if its disconnected. If it is, this'll be the cause of your excessive fuel consumption. When I got mine, the first thing I noticed was an appaling lack of power 'til I noticed the rod had dislocated. It's linked to the butterfly mechanism in the inlet manifold which opens up all 8 ports under heavy acceleration around 3500-4000rpm. Under normal driving, only 4 of the 8 ports are open for fuel economy and all 8 open when you give the chariot some 'shoe pie'! ;)

[talldave]

Is the smell from the cat linked to the poor fuel consumption or are the two unrelated?

I get 33mpg from my 1998 1.8 auto around town - which I consider to be OK ish. However when I push the car hard I also notice a smell that I assume is coming from the cat - it's not that bad though - nothing like dibber describes.

Is the smell from the cat anything to worry about or is it just normal?

[TRIGGER]

Supposedly according to toyota its normal and nothing to worry about, as far as i know renault clios do it aswell, the smell sometimes is quite overpowering though, i get especially concerned when it smells overpowering when i have my 7 month old baby in the car. Can anyone shed some more light on this problem?.

[uumode]

Supposedly according to toyota its normal and nothing to worry about, as far as i know renault clios do it aswell, the smell sometimes is quite overpowering though, i get especially concerned when it smells overpowering when i have my 7 month old baby in the car. Can anyone shed some more light on this problem?.

It is wierd why you can smell the exhaust gases in the cabin, infact worrying? Unless you are driving with the window wound down? I used to get the smell on my old Audi 90, but that was only when I had stopped the car and opened the door, I didn't notice any smell in the cabin.

The smell is due to the sulphur in the fuel, could switching to say Shell low sulphur fuel cure the smell problem?

[talldave]

Sorry - Forgot to say that I normally only notice the smell when I've got the windows open.

[dibber]

Hi m8, i havent got a clue why your fuel consumption is so high, but the smell i get aswell, I have a w plate 2000 1.8gls with only 30000 on it and the cat smells when pushing it hard and when i start it up first thing in the morning, got it an mot emissions test thingy and the cat and all other readings came out normal, also got a garage to check the cat and they said it was k aswell. I would take the car for the emissions test to make sure the cat/lamba sensor etc is k, hope this helped you out a little m8, kind regards TRIG:].

Ok thanks for that. Its due a test in a couple of weeks and I have a friend that does that for me so I will go see him before the test is due to see what the readings are. Looks like a few get the rotten egg smell when they are pushed so it may be a characteristic though mine is pretty bad. Could be tied into my fuel issues though making it worse than normal.

I had similar problems, and my local dealers reported the secondary valve throttle valve on the inlet manifold was stuck.

You could have a similar problem.

That sounds interesting. I just noticed today when its on the warm up cycle it goes great but as soon as its fully heated up it loses an awful lot of power. Is yours a VVTi model?

'Ow do, Fella!

I too own a '98 Avensis with the 7A-FE engine. If yours is the same, have a look at the vacuum rod on the end of the inlet manifold (cambelt side) to see if its disconnected. If it is, this'll be the cause of your excessive fuel consumption. When I got mine, the first thing I noticed was an appaling lack of power 'til I noticed the rod had dislocated. It's linked to the butterfly mechanism in the inlet manifold which opens up all 8 ports under heavy acceleration around 3500-4000rpm. Under normal driving, only 4 of the 8 ports are open for fuel economy and all 8 open when you give the chariot some 'shoe pie'! ;)

Now this does sound intersting cos I noticed low down it seems to go ok once warmed up but as soon as the revs get above 3000 its pretty much gutless. In fact I was going along the motorway the other day at around 70 in 5th and it was picking up nicely so I dropped it into 4th to see what happened and it was gutless. Higher revs obviously.. I know the vacuum capsule you mean so I will look at that also. Thanks

Supposedly according to toyota its normal and nothing to worry about, as far as i know renault clios do it aswell, the smell sometimes is quite overpowering though, i get especially concerned when it smells overpowering when i have my 7 month old baby in the car. Can anyone shed some more light on this problem?.

It is wierd why you can smell the exhaust gases in the cabin, infact worrying? Unless you are driving with the window wound down? I used to get the smell on my old Audi 90, but that was only when I had stopped the car and opened the door, I didn't notice any smell in the cabin.

The smell is due to the sulphur in the fuel, could switching to say Shell low sulphur fuel cure the smell problem?

It makes you wonder how cats can be good for the enviroment with all that sulphur gas they give off. I know a new cat can be very smelly but the one on mine is not new. To be honest I can live with the stinking cat at the moment as the fuel issue is my main concern. I just wondered if the two were linked.

[TRIGGER]

MMM, cant really see it being linked with the fuel, but hey i aint a mechanic, im just giveing my opinion due to me haveing the same smell as yourself, i cant really add anymore, my fuel consumption isnt that good either, i only get around 30 mpg doing short trips, this working aout around £5 per 30 miles, when you find out whats causing your fuel problem including the smell let us know m8, kind regards TRIG:].

[dibber]

Ok will do ;-)

[TRIGGER]

Hi m8, any updates, did you get the problem sorted?.

[Bilal8210]

hey i have exactly the same thing with my 1998 1.8GLS. I only get the smell after the cars had a good long run or after ive been speeding a lil. It does get pretty bad but cant realli smell it untell i step out. I jus presumed it was normal....?

[TRIGGER]

I actually spoke to 2 guys today about the smell, one has a 1.8 99 and the other has a 1.8 vvti 53 plate avensis, both have got the smell, so i take it its normal i think;].

[purvesh81]

I actually spoke to 2 guys today about the smell, one has a 1.8 99 and the other has a 1.8 vvti 53 plate avensis, both have got the smell, so i take it its normal i think;].

@dibber - sorry for the delay, mine is the Mk1 Avensis, so it's not the VVTI

Trigger.. my CAT stinks when driven hard, completely normal....unfortunately (actually quite embaressing when I'm pimpin' with the hunnies )

[TRIGGER]

Thx for confirming that m8, no need for me to worry now:], NOTHING should be embarrasing when pimping with the hunnies, you not what i mean LOL, cheers m8:].

[Mackers]

i'm getting about 31MPG on mine, which does also seem a bit low, i've tried STP fuel cleaner and redex in the past to no joy, also changed the fuel filter.... again no joy, any ideas what it is, mines a "X" Reg 1.8VVT-i, do i have this butterfly valve, if so, where is it??

[dibber]

Ok here is latest update..

I have been busy with work so its taken me a while to get the time to try and suss out the issue.

First thing I did was give it a service as it was getting close to one.

This had zero impact as which i reckoned would be the case anyway.

I checked out the throttle butterfly arrangement and it seems to fuction ok. I even disconnected it to see what difference it makes. It gives a bit of a hestitation when you accelerate at lower revs.. but no really big difference to speak of.

A couple of days after the service and no change to the fuel consumption, which was between 20-25mpg, I decided to take it for a caning on the motorway.

On the first run I had it up to 125 and it was smelling pretty awful but a different smell this time. Not the sulphur smell I usually get. In fact it smelt like something was about to go on fire so I eased up.

On the run back I sat at around 110 and although there was a slight smell off the cat it was nowhere near as bad as it had been.

I probably did 7-8 miles in total. I went to see a friend to get the emissions tested but he was too busy to accomodate me.

The following day I put fuel in it and a few days later I started to think the fuel was lasting really well. Long story short it ended up doing 40mpg. Wow what a difference from 25mpg.

So it looks like that blast along the motorway cleaned something out. I am now onto the second batch of fuel since then and so far its looking good. Wish I could give you something a little more technical on why this is so but if it continues to give that consumption I will be quite happy.

The dealer I bought the car off was telling me it was an old guy that had it and rekoned he just pottered around in it so it was probably clogged up.

The performance is still the same as before though but I can live with it if the fuel return is as good as what it is now.

Thanks for all your help guys.

[dibber]

Latest update... yes I know it was over a year ago I posted originally!

Fuel consumption has been ok but the cat smell has never improved. It passed its emissions no probs again at MOT this year

and left both the guy that does the MOT for me, and myself, scratching our heads as to what it was.

Just the other week whilst waiting for a friend I was just sitting blipping the throttle when I felt a vibration around 4000 revs.

It felt like something was loose and it made a buzzing sound.

The following weekend a friend and I had a look to find out what was causing it and it turned out to be the heat shield around the cat.

The heat shield is two halves that look like they might be riveted together. On one corner the rivet was missing and it was vibrating

really badly when it hit 4000 revs. I put a nut and bolt in it and that cured the noise.

A couple of days later it suddenly dawned on me that the cat was no longer stinking like it used to do. I thrashed it around for the next few days

and the smell has stopped. I can only assume the resonance caused by the vibrating shield was affecting how the cat performed. It was really vibrating badly.

Its only taken nearly two years to get rid of it! Naturally I am over the moon and an added bonus is the car has a bit more grunt than it use to have.

[talldave]

Dibber - are you really suggesting that the smell from the cat has now gone just because you've stopped the heat shield vibrating? This sounds unlikely to me. Have you changed anything else - e.g different petrol for example?

I still get the smell from my cat - I'll be checking the heat shield at the weekend - however there is no noise that sounds like it vibrating.

[dibber]

Dibber - are you really suggesting that the smell from the cat has now gone just because you've stopped the heat shield vibrating? This sounds unlikely to me. Have you changed anything else - e.g different petrol for example?

I still get the smell from my cat - I'll be checking the heat shield at the weekend - however there is no noise that sounds like it vibrating.

100% certain that has been the cause of it Dave. I had to hold the revs steady around the 4k mark to hear it with the car stationary. Under normal driving I was not hearing it at all though I did feel the engine to be "rough" around those revs. As soon as the heat shield was sorted the smell vanished. Its probably got something to do in the way the cat works and the high frequency vibrations generated by heat shield were causing it.

Mine was really stinking! At 100 mph it smelt like something was seriously on fire.

On reflection I should have contacted an old school friend who is in Wales now working as an Engineer for a company that manufacturers cats. I am sure he would be able to explain the science behind it.

[dibber]

Meant to add its not unusual for the cat to smell slightly if the car has been driven reasonably hard under normal circumstances. What you may be getting Dave might be considered "normal"