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Engine Weak/misfire At Full Throttle....


miniblob
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As above really guys...

It's a 2000 W reg Focus, 2.0 16v - which feels more like a 1.4!!! Seems to be holding back!!!

Has been driving ok, feeling fine, other than low on power - idle is good, always starts first time, etc...

However, it has now started to misfire - but only at full throttle!!! Pretty much any revs, put your foot to the floor and it really struggles - no acceleration at all until you back off to maybe 80% throttle, where it drives fine again!!!

Doesn't seem to do it when standing (no load) and revs fine at full throttle then - just struggles under load!!!

I did find a couple of plug leads that didn't seem to be on all the way so I re-seated those properly.

Also found a small earth lead to the top of the engine which had broken off, so I've fixed that.

No difference at all after those two bits - so where do I go from here???

Could it just be dodgy plugs, or something more???

Any help greatly appreciated!!!

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I would change the plugs, leads and the fuel filter (If it has an inline one). Also the air filter.

If this doesn't sort it you need to get the intake system checked for leaks and blocked vacuum pipes. Lastly the coilpack may need checking and replacing.

There are a lot of things that could be causing it but start with the basic serviceable items. It is likely that these havent been changed for a long time.

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Thanks mate - any idea where the fuel filter would be on this car???

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I check it not boging down because of the cat. Had same sort of thing on mine when I shook

it had broke up in side it and I couldn't get above 60

best to get your codes read see if it shows anything

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I'll bear that in mind!!!

Couple of questions:

What size are the spark plugs??? I've got a whole set of spark plug sockets/tools and can typically only find the 14mm!!! These look tiny (10mm maybe???) down that long hole!!!

Also, just quickly glanced at eBay for new plugs and this auction: http://www.ebay.co.uk/itm/GENUINE-FORD-FOCUS-ZETEC-2-0-16V-PLATINUM-SPARK-PLUGS-/400224145076?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item5d2f37ceb4 looks a) too cheap and b) states there are two plugs of one size and two of another!!! Is that right??? All the others are just auctions for 4 plugs or individual plugs - no mention of sizes!!!

Also, anyone know somewhere cheap near Croydon, that might do a quick code read for a few quid for me???

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Surely there's not two plugs of one size and two of another??? Would love to know so I can order some at the same time as another 10mm plug socket!!!

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Must be someone who can tell me if the four plugs should be identical, of if there are indeed 2 x AYFS22P1 & 2 x AYFS22PG1, as per the eBay link above???

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Must be someone who can tell me if the four plugs should be identical, of if there are indeed 2 x AYFS22P1 & 2 x AYFS22PG1, as per the ebay link above???

Long story. Ignition system on the Zetec engine is "Wasted Spark" which means that two plugs are always firing (a wasted spark) on the exhaust stroke. Two plugs fire through the centre electrode while the other two fire through the side electrode. This would normally require double platinum electrodes to make sure that you always had a platinum tip on the firing plug but to save a tiny bit of money, Ford (Motorcraft) made single platinum plugs, some with the platinum tip on the centre electrode and others with the platinum tip on the outside electrode. These plugs had to be fitted in the correct cylinders. With double platinum plugs, you can shove them anywhere. All replacement plugs are double platinum so you don't have to worry about where they go.

The plugs on the eBay link you gave are the original type plugs. If you buy them, you must match the plug part number to the correct cylinder and remember not to get them mixed up at a later date. They are all physically the same size but will have different part numbers stamped on them. They are a good price if you remember to fit them correctly. Might be worth replacing plugs and leads at the same time. Set the gap on any new plugs to 1.1mm. Get any misfire fixed quickly as the unburnt fuel can damage your cat.

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  • 2 weeks later...

Hi guys - still messing around slowly with this!!!

Had a window this morning so changed the spark plugs and ignition leads for new items - still no different.

As before, can't spot anything obvious from poking around under the bonnet... does anyone have (or know of a link for) any decent diagrams of the intake system and vacuum pipes, so I can make sure I've checked it all???

Also, where would the fuel filter be on this car?

To save you reading the whole thread again - it's a W reg 2.0 16v which is hesitating/misfiring under load at above 80%(ish) throttle - fine below that, just a bit slow!!! No warning light, doesn't hunt at idle, etc...

I've found a local mobile mechanic who says he can read the codes (if there are any) for £10, so I suppose that could be the next sensible step???

Any other ideas/suggestions appreciated!!!

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Any ideas for the weekend???

Any intake diagrams you could link to for this car/engine???

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What about the fuel injectors? i had a car that had a similar problem and i had to replace the fuel injectors.

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