Hi All

I have recently diagnosed my intermittant misfire problem to my ht leads (i think)

My engine has been revving rough for quite a while, ever since i purchased my car around 4 months ago.

Then around 1 month ago i removed the ht leads from the plugs and plugged them back in and the car ran perfectly until now again, its started to rev really loudly and lose power feels like its running on 3 cylinders, i have done the same again, took the ht leads off the plugs and put them back on again, and the car is fine again.

So i have decided to get some new leads and plugs

Is this the right thing to do or do i just need ht leads or maybe coil pack, and how long should ht leads last for

Also is it best to get these direct from ford as they will be proper parts meant for the focus.

Any help with this would be great.

My car is a mk2.5 focus 1.6 petrol 100bhp with 43000 on the clock

i would change the leads and plugs and buy them from ford cheap leads do not work so dont waste the money on them ford leads are about £60-70 for the 4 also purchase from ebay some dielectric grease and smear this in both ends of the leads before fitting its what ford do and it helps even out the idle and make sure the plugs are gapped at 1.0mm most are still gapped at the old setting of 1.3mm and ford also changed that to even out rough idle

+1 - Agreed - when i read the OPs post i thought the same thing - change the plugs and leads at the same time and gap the plugs down to 1mm - this puts less stress on the leads and coil packs (these components work together so if one fails - it can damage others) -

Once you have replaced the plugs and leads and it still does not seem right - the next thing is the coil packs - you can choose to do the coil packs as well (eg- the whole lot) but this would be expensive and may not be nessesary (but worn plugs/ faulty leads can "take out" the coil packs)

With the gaps ("gapped down") at 1.0mm the plugs/ leads/ coil packs should last longer - Quality plugs like genuine Ford, or "premium" makes and irridium tipped plugs should last better than "budget" ones

If you do a lot of "round town" driving, start- stop or leave the engine ticking over for long periods this can foul the plugs, reducing their(and the leads/ coil packs) lifespan worn/ fouled plugs can reduce the leads and coil packs lifespan (a "stitch-in-time"/ "knock-on effect") worn bores/ oily residue from the engine breather can foul the plugs

Damp/ wet weather can short the leads (its like lghtning - it finds the easiest path - ) so the car can run well in dry weather and "miss" in the wet - a narrower gap (and the above) helps here too

Would the 1.0mm plug gap apply to my 2006 Mk2 2.0 petrol as well?

Would the 1.0mm plug gap apply to my 2006 Mk2 2.0 petrol as well?

The same princepals apply - (on any )

A wider gap (eg 1.3mm) may give a "fatter" spark and MAY help the mixture combust more efficiently in the combustion chamber (eg potentially better emmisions) BUT a wider gap puts the plugs, ht leads and coil packs under more strain, and are more liable to fail

The HT (high tension) part of the ignition circut is like lightning - it finds the easiest path - this is fine if all tghe HT components are in good condition (the spark occurs at the plug tip- where it should)

Over time the plugs wear and the gap gets (slightly, but its significant) bigger, the plugs become foulded with carbon and sometimes oil (from worn bores/ guides or from the crancase breather depositing oil into the intake, to be ingested by the engine) - the easiest path may then be, deeper inside the plug, shorting of the HT leads or even a short inside the coil packs

A narrower gap means the spark is more likely to occur where it should at the spark plug tip - even as the plugs wear/ become contaminated, or if the HT leads are not in tip-top condition (or as a precaution)

Of course, there must be a gap to form a spark and if the gap is TOO small it will produce a smaller spark

But i am led to believe that Ford recommended 1mm gaps, then 1.3mm, then reverted back to 1mm for some of their cars, there must be a reason for this (potentially as outlined above)

I have reduced the gap down to 0.7mm (the recommended gap on some older cars) on cars with faulty coil packs/ leads (this was a temporary "fix" ) and they started to run well again

1.0mm for all petrol focis the 1.3mm was causing rough idling and also was attributed to the coil packs failing quickly ford found 1.0mm was far better and have stuck to it yet most plugs are pregapped at 1.3mm

Thanks for the advice.

I have just ordered some plugs and leads from tc harrisons ford and it only cost me 60 quid. Plus if I wanted a new coil pack they only charge 65 quid. Not bad for a ford dealer.

Artscot69 with the Dielectric grease, how much do I need to put on the leads. And do I smear it all over the metal connectors on the end of the leads

put a small blob of it on the leads to the plugs and a small blob on each coil connector and yes you want good coverage on the inside of the leads i found a cotton bud to be an easy way to apply it to the inside of the leads

are they genuine parts as four leads work out at over £60 on there own and even from ebay a genuine coil is £30 plugs are £7.00 each so either way its a cheap deal hopefully they arent cheap leads as they cause nothing but misfire hassles

They are genuine ford parts as he went through the ford etis to find the parts

He must be the cheapest ford dealer there is with vat added the leads are £61.57 the plugs £28.00 the coil pack 87.30

hes likely not added the vat yet but heho youll know if they are genuine by looking at them

Leads were roughly 10 quid each without vat so not much extra, plugs were 3.00 plus vat. They have a half price sale on plugs aswell at the moment. And if they turn out to be cheap parts I won't buy them, as I asked for genuine ford parts. Didn't realise ford dealers did cheaper patented parts.

Sounds like you got a good deal. They do them i found out when i got new leads and had 2gen ford and 2 cheap ones so went back in and demanded what ide paid for the guy told me they use cheaper parts for cars such as mobility cars etc and some people want cheaper parts as well so they do various makes of part for s clutch ford will do whatever brand they use but if its too expensive they will order a cheaper make to give the customer a deal

Just collected my order from Ford TC Harrisons Burton-On-Trent and 4 leads and 4 plugs came to £65 which included vat. They are all genuine ford parts. Each ht lead came to £12 including vat and each plug around £4.

See picture below of my order

I have also purchased some copper grease for the plugs but i couldnt find any dielectric grease.

Gonna let the car cool down first then crack on with changing the parts

Well i have changed all leads and plugs, rather easy for a first attempt ever. Just had a couple of issues with getting the leads to stay plugged onto the coil pack. One of the leads kept popping off, seems ok now but will keep and eye on it

if it keeps popping off it will continue to i had this with lead 1 i got pliers and a rag wrapped the rag round the plug end of the rubber and squeezed the rubber where the metal contacts were so it was a tight fitting otherwise it pops off and you get the misfire again did you gap the plugs at 1.0mm

Ford said the plugs were already gapped at the correct spec. Might try crimping the lead to keep it on, I am also expecting some Dielectric grease tomorrow to come through the post so I can Also sort out that

Yeah they told me that too and on the service i was told they were at 1.3mm and not 1.0mm as they should be they are bosch plugs and despite the ford logo are made to the same spec as the ones in any shop which are gapped at 1.3mm always best to check mate

Yeah they told me that too and on the service i was told they were at 1.3mm and not 1.0mm as they should be they are bosch plugs and despite the ford logo are made to the same spec as the ones in any shop which are gapped at 1.3mm always best to check mate

+1 - my thoughts exactly - the "correct" gap (according to Ford) could be 1.0. or 1.3mm

I have got some Wynns multi lube spray which is a very strong Dielectric spray, that should do the job

Alll is now done and the car runs much better, but i am geting a slight rumble sometimes when the car is at idle, dont think its that bad that the car would stall, but the revs do flicker around very slightly, what could be the cause of this