Vauxhall Corsa Misfiring when cold

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2007 Corsa, 1.4. Roughly 88k miles.

So about a year ago I had the flashing engine management light come on while I was sat at some traffic lights having only started the car a minute or so before. Took it in to the garage and they replaced the coil pack. Told me it was misfiring. All was good and I was getting more MPG.

Maybe a month or so later, the MPG slowly got worse again. Can't remember if the warning light came on again, pretty sure it did at some point. Come June this year it failed the emissions test at the MOT. They replaced the coil pack again for free, and changed the plugs and all was good. Although the mechanic said it was running a bit sluggish. It's always felt sluggish since I've owned the car. It did increase MPG, by about 60-70 miles a tank.

Again that didn't last long. Got the warning light again, but it only ever seems to be when the engine is cold. Feels like it is going to stall.

So here we are now and I'm forever revving the engine when idling to avoid the warning light coming on. Car tends to idle around 7,000 rpm. The one time recently I forgot to do this, warning light came on, again.

Also, I don't know if it's my imagination but the car feels less sluggish after I've filled the tank up with petrol!!!

Does anyone know the cause of this? I know I need to take it back to the garage, will save me money in the long run, but I'd like to know what might be causing it and what the fix would be.

Thanks
 
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It reads as that is another misfire. You should be able to find out which cylinder by comparing the colour of the sparkplugs whilst it has just done it. Maybe coil pack again, or a sparkplug.
 
It reads as that is another misfire. You should be able to find out which cylinder by comparing the colour of the sparkplugs whilst it has just done it. Maybe coil pack again, or a sparkplug.

Thanks. I was just wondering if it is coil pack, why it would be failing again so quickly. Is there something else that can be causing it?
 
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Probably wouldn’t hurt to put a new set of HT leads on it.
 
Coil pack. Singular. They have leads. Coil per cylinder (pencil coils) that mount directly on top of each spark plug do not have HT leads. Edit - are these the ones that have 4 coils in one unit? Fitted plenty of Ford coil packs and they have ht leads. Edit 2. Just looked online and yes, they are the ones with 4 coils in one so yes, no HT leads.
 
If the engine management light has been on, then a fault code will have been stored, and should be read.
Maybe if the fault is more prevalent when cold, the coolant temperature sensor may have something to do with it but throttle body problems aren't unknown and manifest with a poor idle.
John :)
 
More likely to be out of resistive tolerance, Harry.....early VW's were notorious for this. Basically, the resistance is very high when cold, decreasing if it warms - if its out of tolerance or not changing quick enough, the engine's ECU doesn't alter the fuelling.
Naturally, a guess, of course!
If petrol motors are a bit down on power for no apparent reason, I take the (first) Lambda sensor out just in case there's a cat problem.
John :)
 
Basically, the resistance is very high when cold, decreasing if it warms - if its out of tolerance or not changing quick enough, the engine's ECU doesn't alter the fuelling.

A cheap diagnostics unit should report the temperature value too. My three all do.
 
Unfortunately my Foxwell gear (around £300 I think) refuses to connect with vehicles 67 plate and younger which is a real bore :(
Ive only scanned French stuff so far but it wouldnt read a BMW mini either.....looks like the writing will be on the wall for DIY stuff soon.
John :)
 
Unfortunately my Foxwell gear (around £300 I think) refuses to connect with vehicles 67 plate and younger which is a real bore :(
Ive only scanned French stuff so far but it wouldnt read a BMW mini either.....looks like the writing will be on the wall for DIY stuff soon.
John :)
What Foxwell gear do you have? I have a NT644Pro. Bought it in 2016 and only found out a few months ago it has free lifetime updates.
 
My mistake bud, its actually a Gendan GCR 10.....a bit long in the tooth now but I can hardly justify an up to date replacement! It has certainly served me well.
John :)
 
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