Ford Fiesta - Ford Fiesta lack of power - possibly catalytic con

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Mon 4 Jan 2016 22:51
Ford Fiesta - Ford Fiesta lack of power - possibly catalytic con - TypicalSuch

Hi there,

Just wondering if anyone can help me - I currently have a petrol ford fiesta 2000 reg with approx. 87k on the clock. Recently there has been quite a noticeable loss of power - mainly on hills and any incline for that matter! Whenever I accelerate, I struggle to climb at any respectable speed as it just doesn't pick up speed well. It's not misfiring - I dI'd have a few issues with misfiring early-mid last year where the coil pack, spark plug and HT leads all decided to go on separate occasions.

I was told by a large chain garage that they think the exhaust pressure seems low so they are guessing it's the catalytic converter needs replacing. My personal OBD device shows no error codes, however my bank 1 sensor 2 oxygen sensor (after the cat) is stuck on 1.27V when viewing live data, despite the bank 1 sensor 1 oxygen sensor (before the cat) fluctuating probably not much past 0.6V. Why is sensor 2 not changing at all?

I understand that the misfire could maybe have damaged the cat? I tried not to drive it as soon as possible, however the first time I drove it for probably a couple of weeks in which it was a little juddery when accelerating - I didn't actually realise it was misfiring!

Is it more likely to be the catalytic converter or the oxygen sensor? If it's the catalytic converter, does the root cause sound like the misfire or could it be the post-cat O2 sensor? Obviously these components aren't the cheapest in the world so I don't really want to replace them unnecessarily, but I do find it strange why sensor 2 isn't changing at all on my live data OBD.

Thanks in advance to anyone who can give their suggestions - much appreciated!

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Mon 4 Jan 2016 23:27
Ford Fiesta - Ford Fiesta lack of power - possibly catalytic con - elekie&a/c doctor
There are a lot of numbers ,figures and possibles being thrown around here.I would get a garage to remove the top oxygen sensor and plumb in an exhaust back pressure gauge.This will give an exact reading as to whether there is a blockage in the system.Could be the cat,or further down the line.Btw,the sensor 1 should fluctuate at around 1 second intervals,the sensor 2 should remain at a steady voltage of around .5 volts.(rough guide)
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Tue 5 Jan 2016 08:08
Ford Fiesta - Ford Fiesta lack of power - possibly catalytic con - Railroad.
You can diagnose a blocked exhaust, and a whole load of other faults by measuring inlet manifold vacuum. In fact the job's even easier if your car has a MAP sensor because you can read the live data with a scantool. Manifold vacuum at idle should be around 20in-hg on a gauge. Snap open the throttle quickly and let it close and the reading should drop to zero before quickly returning to above 20 initially before settling at around 20in-hg again. If after the throttle closes the gauge is slow to return you have a blocked exhaust.
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Sat 9 Jan 2016 09:11
Ford Fiesta - Ford Fiesta lack of power - possibly catalytic con - KenC

If the exhaust pressure ( from the tailpipe) is in fact low It could be a blocked rear silencer box ( meaning it has rusted away internally and collapsed ). If the exhaust flow has been blocked this may be relevant.

It is a 16 year old car if you intend keeping it (unless you know when the rear box was last changed ) I would replace it they are CHEAP at euro car parts.

Edited by KenC on 09/01/2016 at 09:12

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Sat 9 Jan 2016 12:15
Ford Fiesta - Ford Fiesta lack of power - possibly catalytic con - Cyd

16 years old and 87k on the clock = very low mileage so I'm guessing it does a lot of short journeys. N'est pas?

in that case I'd suspect an exhaust box rotted out internally and collapsed. the water vapour in the exhaust condenses in the cold system and absorbs gases to produce acid which rots the internals. This is one reason regular long journeys are good - warms up the entire system and dries it out before it's park up.

you could drill a 5mm hole before and after each box to check the flow at various points in an effort to find the blockage. Bung up with gun gum and a worm clip after.

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