zetec coil pack question

[steveo3002]

can a coil pack be weak /low performance without causing a misfire or fault code?

ive been chasing a bad idle problem on a focus , just read that ford reccomend a plug gap of 1mm instead of the original 1.3mm , due to coil problems /damage? jut changed mine to 1mm and it runs a bit nicer but still not right , wondering if it could use a fresh coil yet it doesnt misfire or log any faults relating to that

[stevieturbo]

steveo3002 said:

can a coil pack be weak /low performance without causing a misfire or fault code?

ive been chasing a bad idle problem on a focus , just read that ford reccomend a plug gap of 1mm instead of the original 1.3mm , due to coil problems /damage? jut changed mine to 1mm and it runs a bit nicer but still not right , wondering if it could use a fresh coil yet it doesnt misfire or log any faults relating to that

Given most coils are more powerful than needed, yes.

But are you saying there is or isnt a misfire ?

As for whether a misfire is reported, also depends how it is detected. Some systems might be better than others at reporting, some could be terrible and misleading.

[drmotorsport]

More likely to be the idle control valve than the coilpack i would have thought, a common issue on these engines. A dying coil pack tends to show issues more at higher revs.

[steveo3002]

no misfire recorded or noticed

its had isv , pipework, pcv valve , tb cleaned out and nothing effected it at all , changing the plug gap has made a noticeable difference so it made me wonder if smaller gap = less load on the coil and maybe its babying a weak coil

i guess i can try a ebay special see if its any different for what they cost..

[GreenV8S]

Usually, a bigger gap results in more energy in the spark so it lights the charge better, but an excessive gap may mean the ignition system can't actually generate a spark under some conditions - so you might get a misfire at high rpm high load, for example. It seems strange for an engine which runs without a misfire with a larger gap to run better with a smaller gap.

[stevieturbo]

What does a gas analyser say ? That will tell you straight away if there are any misfires as hydrocarbons will be very high.

If no misfires, then it would be hard to look in that direction for the problem.

Are they the correct plugs for the engine ? Some can be fussy.

[steveo3002]

dont have a gas tester so no idea

correct spec bosch plugs in it at the moment , havent heard any tales about them not liking certain brands

[GreenV8S]

When you say you changed them from 1.3mm to 1mm, did you re-gap the same plugs or was this actually a plug replacement?

[steveo3002]

re gapped what i had

[oakdale]

More likely to be faulty HT leads than coil pack.

[Wait Here Until Green Light Shows]

steveo3002 said:

no misfire recorded or noticed

its had isv , pipework, pcv valve , tb cleaned out and nothing effected it at all , changing the plug gap has made a noticeable difference so it made me wonder if smaller gap = less load on the coil and maybe its babying a weak coil

i guess i can try a ebay special see if its any different for what they cost..

The opposite is true...Smaller gap = lower resistance = more 'load'.
A smaller than spec gap may overheat the coil or switching mosfet.
I would be tempted to pull out one of the plugs and observe the quality of the spark at different gaps. A smaller gap will be hotter and quite white in colour...a larger gap will have more of a blue tint to it. If it fails to jump a slightly larger gap then you will know for sure it's the coil.

I would also check the colour of each plug. If one is significantly different to the others then you may have a dodgy lead. Are they all a nice tan colour or sooty etc.

[steveo3002]

theyre all an even colour and it runs nicer at 1mm so i will stick with that

google suggests the change from 1.3mm -1mm was due to premature failings of the coil with the gap at 1.3? so would say to me an increased load but what do i know lol

[Mr2Mike]

Wait Here Until Green Light Shows said:

The opposite is true...Smaller gap = lower resistance = more 'load'.
A smaller than spec gap may overheat the coil or switching mosfet.

A smaller gap requires less secondary voltage to initiate an arc, which means lower primary voltage. Reduced stress on all parts (HT leads, coil insulation and coil drivers) is the result.

Once initiated, the resistance of the plasma in the spark gap is miniscule and the gap will make little difference.

The opposite is true; the wider the gap the greater the stress on everything, which is why operating an ignition system without a spark gap is such a bad idea.