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Ford Focus Mk1 99/T 1.8 petrol - Badly reduced fuel economy - Ovation1357

Hi All,

For most of my car's life I've easily achieved >200 miles on a tank before reaching the halfway mark, and a minimum of 360 miles before seeing the fuel light. For the last couple of years the fuel economy has been much worse and it's finally time that I do something about it!

I'm now lucky if I get 160 miles on half a tank and ~290 from a tank.

I'm not totally sure if the drop was sudden or gradual but I'm really noticing how often I have to fill up now.

I've eliminated things like tyre pressure/condition and despite having a small oil leak, it seems to make no difference whether the car is a Max or Min oil level.

One thing I haven't changed for several years is the fuel filter, but despite a friend suggesting it as a possible cause I can't really see how it could cause the car to use *more* fuel?? I almost exclusively buy Shell fuel and never buy cheap supermarket stuff.

Can anyone give me some pointers of things that I should test (and perhaps how I can test it/them)?
I've got a decent multimeter and have access to an oscilloscope if necessary too.


Thanks in advance
Jonathan

Ford Focus Mk1 99/T 1.8 petrol - Badly reduced fuel economy - Peter.N.

I would have thought that if you were using that much extra fuel that it would have failed the emmissions test, if emmissions are normal I would look somewhere else other than ther engine for the problem.

Ford Focus Mk1 99/T 1.8 petrol - Badly reduced fuel economy - 72 dudes

Air filter blocked or dirty?

Spark Plugs?

MAF sensor?

Or maybe just old age.

Ford Focus Mk1 99/T 1.8 petrol - Badly reduced fuel economy - Ovation1357

Thanks for the quick responses..

I've never had any emmissions problems at MOT and I've had as least two of them since the economy got worse..

Air filter and Spark plugs have been replaced at least once since this started and had no effect. Is there an easy way I can test the MAF sensor?

Is the anything that could be faulty with the engine itself that could cause such excessive fuel consumption and not seriously affect the emmissions?

There's certainly plenty of wear and tear on the chassis - I had to replace the wishbones last year because the balljoint gaitors had split. When I did this, I found that the bushes in the wishbones were very knackered.

13 years on I am still running it with all the original suspension / drive shafts, etc. At 190K miles I'm fully expectant that there may be significant wear in some moving parts but I'd have expected that to cause the economy to get gradually worse?

I haven't checked the shocks recently but they weren't showing any signs of leaking last time I lookes.

I think I'm tempted to pay a local mechanic to give the car a full appraisal and give me a list of all the problems he can find.. But this car has been so rock solid for the 10 years that I've owned it, I'm feeling quite keen to keep it going, even if it costs me a few days working on it.

Any other suggestions/advice would be much appreciated?

Ford Focus Mk1 99/T 1.8 petrol - Badly reduced fuel economy - bathtub tom

Tracking/wheel alignment? You say you replaced the wishbones, have you got it checked since?

Ford Focus Mk1 99/T 1.8 petrol - Badly reduced fuel economy - ohsoslow

May be a binding brake? After a drive feel the wheels to see if they are hot.

Ford Focus Mk1 99/T 1.8 petrol - Badly reduced fuel economy - BenG

Faulty coolant temperature sensor, causing the engine to run rich in 'warm-up' mode all the time?

Faulty lambda sensor in exhaust, giving inaccurate feedback to ECU causing engine to run rich?

Ford Focus Mk1 99/T 1.8 petrol - Badly reduced fuel economy - mikej

Your initial observations fit with mine - I used to reliably get around 340 miles before the fuel warning light used to come on in my 1999 1.8 Focus Zetec - it had done nearly 90k miles when I traded it in.

IIRC, I used to get around 32-33mpg. 290 miles from a 55l tank is around 24mpg, which is obviously pretty low unless you've suddenly developed a VERY heavy right foot !

How many miles has the car done since the fuel filter was last changed ? Pretty sure I only changed mine once, at around 60k miles, and I don't remember seeing any difference in the fuel economy.

Nothing wrong with supermarket petrol BTW.

Ford Focus Mk1 99/T 1.8 petrol - Badly reduced fuel economy - middle_lane

Hello Jonathan - Did you ever sort this out? I have the identical problem with the identical car (Focus 1999 1.8, 135k miles - yes lots). Has gone abruptly from 10 years of rock-steady 39mpg / 8.7 kpm to about 25 mpg / 5.5 kpg. Also feels flat and once lost compression completely. Suspect I am running a too-rich mix. Garage tested emissions and they're fine. Thanks Roy