Hesitant,Misfire????

[2ky]

I have a 2009 1.6 Ford focus and over the last month I have had a few problems. The car delveloped a misfire on a trip to South Wales so I called the AA out and they noticed that one of the HT leads had lifted off the coil pack slightly and corroded.He cleaned it and we carried on with our journey,the car seemed ok for a while but the misfire returned! I changed the faulty HT lead for a genuine one from Ford and that cured the big misfire.
However! The cars just not right,when its cold if you take the revs upto 2000rpm+ it misfires but once its done that for a few times/warmed up it's fine and will rev like normal. The idle is very slightly lumpy,almost impossible to detect but its not 100% smooth.If I accelerate (down a slip road for example) the car again feels hesitant almost as if the throttle is being lifted off for a second or touching the brakes?
The throttle is a little jerky and with light throttle the car seems to lurch forward for a brief second?
I've replaced all the HT leads and I'm tempted to change the coil pack but would the coil pack cause the issues I mentioned? When the corroded HT lead was removed some of the green corrosion was on the connection between the coilpack and the HT lead. I cleaned the connection on the coilpack using a scourer but would the green corrosion of damaged the connection?

Any ideas welcome!!!

[SV8Predator]

You can't replace anything until you've pulled some codes from it and find out what's wrong!

[2ky]

Yeah but the engine management light hasn't come on! From what I understand a code is only logged if the EML is illuminated but I might be wrong?
Might disconnect the battery for an hour or two tomorrow and see if that resets the parameters in the ECU?

[SebastienClement]

Sounds like an ignition problem if replacing the lead fixed it for a while.

I'd replace the coil pack + all leads and see how it goes.

[Blue Oval84]

Well I had a coil pack (or HT lead) failure today, I got a brand new coil pack and set of leads from a local motor factors for £35 and the problem has gone away. I think the coil pack on it's own was about £15.

For what it costs I would just change the coil pack and see what happens. The parts were so cheap I didn't even bother trying the leads first, just changed the lot and it seems to have worked...

[Andyjc86]

Blue Oval84 said:

Well I had a coil pack (or HT lead) failure today, I got a brand new coil pack and set of leads from a local motor factors for £35 and the problem has gone away. I think the coil pack on it's own was about £15.

For what it costs I would just change the coil pack and see what happens. The parts were so cheap I didn't even bother trying the leads first, just changed the lot and it seems to have worked...

Not all coil packs are cheap though. Most are about £40-£50 so could be an expensive gamble.

What condition are the plugs in?

[Blue Oval84]

Andyjc86 said:

Not all coil packs are cheap though. Most are about £40-£50 so could be an expensive gamble.

What condition are the plugs in?

Sorry should have pointed out mine was a Focus 1.8 coilpack

[Buff Mchugelarge]

Blue Oval84 said:

Well I had a coil pack (or HT lead) failure today, I got a brand new coil pack and set of leads from a local motor factors for £35 and the problem has gone away. I think the coil pack on it's own was about £15.

For what it costs I would just change the coil pack and see what happens. The parts were so cheap I didn't even bother trying the leads first, just changed the lot and it seems to have worked...

Most problems go away if you throw enough money at them

Unfortunately, my ex is still around

[andy-xr]

I'm putting £5 on coolant temp sender being duff

[Blue Oval84]

Buff Mchugelarge said:

Most problems go away if you throw enough money at them

Unfortunately, my ex is still around

Ah, that kind of problem will remain as long as there is any money being thrown around...

[2ky]

andy-xr said:

I'm putting £5 on coolant temp sender being duff

Hhhmmm this is a new possibility that google hasn't come up with! Anymore info why this would cause it?

[andy-xr]

2ky said:

andy-xr said:

I'm putting £5 on coolant temp sender being duff

Hhhmmm this is a new possibility that google hasn't come up with! Anymore info why this would cause it?

If it's doing it from cold then there's a possibility that the ECU thinks the coolant temp is minus three hundred and twelvty and puts more fuel in, which overfuels, which causes a misfire. I'm only putting £5 on it because I'm not that sure

[SV8Predator]

2ky said:

Hhhmmm this is a new possibility that google hasn't come up with! Anymore info why this would cause it?

So you're using Google and internet forums to diagnose your fault when the manufacture has very kindly fitted an on-board diagnostics system to your car?

Read the codes and find out what's wrong with it! It's got nothing to do with the MIL light.

[2ky]

SV8Predator said:

So you're using Google and internet forums to diagnose your fault when the manufacture has very kindly fitted an on-board diagnostics system to your car?

Read the codes and find out what's wrong with it! It's got nothing to do with the MIL light.

Ok,Cars been to the mechanic and plugged into the diagnostic machine,no error codes as I thourght!
The mechanic thinks it could of been dodgy fuel (I think the misfire/hesitation did start the day after I topped up with Asda fuel but that was back in November),First of all he suggested changing the fuel filter so I gave him the go ahead. I got a call shortly after to explain that my car has a "lifetime" filter that is in the petrol tank!
I picked the car up (without having the filter changed) and he suggested using a fuel cleaner and running a tank of Optimax,I've now done this and the car is still the same?
Not sure what to do next really? I'm not a mechanic but I dont think the problem is with the fuel filter, I cant see how a blocked filter causes the car to jerk/buck on part throttle when going around a round about for example (only seems to jerk/buck going around slow corners/round abouts,its almost as if someone dabs the throttle for a split second)? I understand how it can cause the hickups higher in the rev range (3-4k rpm) as the engine requires more fuel which could be restricted due to the clogged filter.
Tempted to get rid of it right now!!! any ideas???

So far the car has had:

New plugs,Coilpack,Leads,Fuel additive and a tank of Optimax.

[furrywoolyhatuk]

Have you checked the plugs?