2003 Focus down on power and high fuel consumption - Help!

MrSix · 16 Dec 2011 at 18:32

My girlfriend's 1.6 Focus is being a right thirsty, slow beggar at the moment.

The best way to describe it is that the power delivery doesn't feel any different to standard, but it's way down. So still smooth and obviously picks up at high revs, but it's just awfully slow compared to how it was 6 months ago.

It's also using fuel at a crazy rate, we're talking a £70 tank gone in less than 200 miles. That's on 70mph motorway cruises at 5th gear too, so it's not down to erratic driving.

Any ideas guys?

ChrisD. · 16 Dec 2011 at 18:34

When's the last time it was serviced? Could be any number of things tbh.

TaKeN · 16 Dec 2011 at 18:35

MAF Sensor? Lambda Sensor?

MrSix · 16 Dec 2011 at 18:38

Recently serviced, no binding brakes, apparently lambda sensor was replaced less than 3 months ago, however I went under the car yesterday while having new tyres on it and couldn't obviously tell that the sensor was new...so not sure if it actually was replaced.

I presume these cars have diagnostics ports like the VAG range and a VAGCOM equivalent that we could get it checked to see if it's throwing any codes?

Dogbreath · 16 Dec 2011 at 19:24

Cat or exhaust silencer blocked maybe. This gives a big hit to power and economy.

MrSix · 17 Dec 2011 at 08:31

Dogbreath said:
Cat or exhaust silencer blocked maybe. This gives a big hit to power and economy.

What's the best test for this? Would it be instantly noticeable if I felt the pressure of the gas coming from the exhaust? And thinking about it...could that increase the smell of fuel / exhaust gas inside the cabin?

Dogbreath · 17 Dec 2011 at 10:02

Just re-read your first post and noticed you said the engine still revs ok? That would actually tend to discount blocked exhaust as this makes the engine more reluctant to rev. The best way to test for this is to measure exhaust back pressure, though measuring engine inlet vacuum can also give a pointer.

An exhaust smell inside the cabin could point to an exhaust leak, which if upstream or at least near to the lambda sensor could also cause overfueling as the sensor can see excess oxygen in the exhaust.

MrSix · 19 Dec 2011 at 08:01

Yeah the car seems to rev fine still. I did check the exhaust system for leaks whilst it was up on the ramps and it's fine from the end of the downpipe through to the back box, but not sure about further up towards the engine.

Would a dodgy lambda throw a fault code?

LEK-89 · 19 Dec 2011 at 10:25

MrSix said:
Yeah the car seems to rev fine still. I did check the exhaust system for leaks whilst it was up on the ramps and it's fine from the end of the downpipe through to the back box, but not sure about further up towards the engine.

Would a dodgy lambda throw a fault code?

A dodgy lambda would throw up the emissions light on the dash as well as a fault code on the ECU.

Liam

MrSix · 19 Dec 2011 at 10:58

hmm...no dash light, but will report back about fault code.
This really is a strange one to diagnose.

Muffin` · 19 Dec 2011 at 11:13

What kind of o2 sensor, ebay special or Ford part?

MrSix · 19 Dec 2011 at 11:21

O2 = Lambda?
If so then I presume they've used a genuine Ford part.

Muffin` · 19 Dec 2011 at 11:30

Yeah sorry, Lambda. I'd check that it is a 'proper' one. You can get lucky with cheap ones but they can also just not work and give you the symptoms you're experiencing. It may not be tripping the fault's as as far as the ECU is concerned it's working properly

MrSix · 19 Dec 2011 at 11:39

Cool beans, thanks for the heads up. I'll get it checked out and see.
It's soul destroying to see how much she's paying in fuel though, her commute is less than 10 miles round trip and she's spending almost £120 per week on fuel!

Dogbreath · 19 Dec 2011 at 12:08

MrSix said:
Cool beans, thanks for the heads up. I'll get it checked out and see.
It's soul destroying to see how much she's paying in fuel though, her commute is less than 10 miles round trip and she's spending almost £120 per week on fuel!

That must be horrendously overfueling! This can easily damage the cat through overheating so better to sort it sooner than later. Longer term it will cause premature bore wear.

Is it definitely not misifiring? When were the plugs last changed? Ever had a new coil pack or HT leads? A misfire causes a lean condition as it pumps air into the exhaust, so you get a double whammy of overfueling and being down on power and needing more throttle.

Jonnycoupe · 19 Dec 2011 at 12:12

A lazy thermostat could be not getting the car up to temp which wouldn't be helping either. Does the temp gauge get to midway? That said I dont know if the gauge sendor and ECU sensor are the same unit.

Has a mouse made a home in the airfilter housing?

ShakenNstirred · 19 Dec 2011 at 12:39

Jonnycoupe said:
A lazy thermostat could be not getting the car up to temp which wouldn't be helping either. Does the temp gauge get to midway? That said I dont know if the gauge sendor and ECU sensor are the same unit.

Has a mouse made a home in the airfilter housing?

yes i had this on my polo, wasnt getting up to temp so was always on cold engine map and was only doing like 30mpg
changed the thermostat and its now up to full temp and mpg is close to 45