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mk1 1.8 petrol focus misfire


dhr90
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My car has had an intermittent misfire for a while now, but I only noticed it on the odd occasion, now its become a lot more frequent/constant.

Symptoms: 

Down on power throughout the rev range and whichever gear I'm in.

Sounds rough, quite a lot of vibration at 55-70mph. Once I get below 45-50 again this tends to dissipate though. If I slow right down and stop, then go back up to 50ish the noise and vibration is much gentler.

 

I've taken the spark plugs out, and the electrodes all look the same and as they should. There was a little oil I had to clean up out of around plug 1 before I removed the plug, but that is a whole other issue I think, as it isn't leaking or burning away very much I'm not too worried about it just now.

My dad has a 20-30 year old coil voltage tachometer (flashes a light every time the coil pack sends voltage to each spark plug), which when connected between the coil pack and each HT lead in turn showed there is a variation in the timing of the spark for each cylinder, but that some cylinders were worse than others. 4 was much worse than 1, but none were perfect.

So, is this a likely coilpack replacement? If so is there any brand to look for or to avoid? Eurocarparts has a HAAS brand for £18, vs Bosch for £66, or fordpartsuk has one for £45. The HAAS one sounds too good to be true to me.

EDIT: I should add, I have plugged an OBD reader in and it hasn't found any codes, would have thought a misfire might create a code?

 

Side note, can anyone confirm that the part circled in red the below image is an earth point for the engine? Whatever it is, on mine, it had corroded/rusted away so much that the wire had simply snapped itself away from the crimp. Have replaced it with some nice bright yellow and green earth wire and new crimps, ended up using two pieces of wire in parallel to make up for the reduced diameter (only fractionally smaller in all honestly). It looks a bit out of place with the grease, oil, dirt and rust of the rest of the engine bay now :laugh:

 

focus engine.jpg

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From the picture that looks like the engine hoist mount thing (has a name I can't think of.. )

Possibly being used as an earth too. As above, sounds like it's time for a new coil pack

www.yorkshiredetailing.co.uk - approved resellers of the Highest quality detailing & Valeting supplies

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On 07/02/2016 at 10:06 PM, artscot79 said:

yes its an earth point

the coil packs a known issue go to ebay you'll get a Bosch coil pack which is what ford use cheaper also ide replace plugs and leads

Is there a reason/need to replace plugs and leads also? Having just been made redundant, I'm trying to keep costs to an absolute minimum.

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Have you used a meter to check the leads? I had the faintest of misfires only felt under acceleration, had it for 18 months, it was only when I actually used a meter to check the leads that I found one of them was 'away'.

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if the issue is with a lead and you replace the coil it will ruin the coil same with the plugs etc so as a rule of thumb you replace all the coil is £30 plugs about £12 the leads are more expensive try the coil and plugs if the misfire is still there you'll need leads

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23 hours ago, Russ said:

Have you used a meter to check the leads? I had the faintest of misfires only felt under acceleration, had it for 18 months, it was only when I actually used a meter to check the leads that I found one of them was 'away'.

No, but its a good idea. Shouldn't be a problem to do that. This misfire is only faint at low speeds, but when it starts at 50+ it can vibrate so much the rear view mirror shakes enough that you can't really see anything in it clearly.

22 hours ago, artscot79 said:

if the issue is with a lead and you replace the coil it will ruin the coil same with the plugs etc so as a rule of thumb you replace all the coil is £30 plugs about £12 the leads are more expensive try the coil and plugs if the misfire is still there you'll need leads

Hmm, may replace the lot then. Prospark leads for £20 from eurocarparts isn't too bad really.

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