KIA Magentis 2.7 misfire....

KIA Magentis 2.7 misfire....



Original Poster:

930 posts

87 months

Friday 1st September 2017
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Right, weird one (I think). I have a 2008 KIA Magentis 2.7 V6 (later shape, really popular, they only sold 60 in three years!) with 60.000 miles and full history. Runs well normally but, if you start it and let it idle for 30 seconds, the check engine light comes on and it misfires quite a bit. Turn it off for a few seconds and re-start it and it's fine again. It's also started doing it in traffic now (it used to be fine once it had warmed up) if left idling in gear (or out) for 20 - 30 seconds and on the motorway the other day it started doing it while at 70mph, which was fun - can't just turn it off and on again in the middle of an overtake!

Code reader just says 'random multiple misfires' and if you break it down it just lists all 6 cylinders as having misfires. It has had new plugs - no change, and it feels so random it must be something electronic but I don't know where to start.

To be honest, it's done it ever since I got the car (about 14 months ago) and I had it serviced and MOT'd which it passed and it made no difference and no fault was found. It is getting worse...

It is the 'dog car' so not terribly in love with it but other than this, it's quite a pleasant old barge with all the toys so loathe to throw it away but also do not want to spend any great amount of money on the thing!

Any help is much appreciated.


3,562 posts

82 months

Friday 1st September 2017
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From what you say, I would be crawling all over EVERY electrical connection under the bonnet & undoing, cleaning, remaking all as a starting point.

I assume it has a coil per cylinder, so that wouldn't be common, I assume it is multi-point injection, so that won't be common, try engine earths also, remove them then properly wire-brush them & re-do them up.


332 posts

107 months

Tuesday 5th September 2017
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Put a picture up of the engine with the cover off if it has one. I can't think what it looks like from memory. If it's random multiple misfires its normally means a component that is responsible for providing for more than one cylinder is faulty i.e a waste spark coil, you may have 2/3 coils to feed 3/2 cylinders each. Start simple anyway.

What type of coil does it use? If it's pencil coils next time it starts misfiring start at one end and unplug each pencil coil. If it makes the engine worse when unplugged that cylinder/coils OK. If it makes zero difference to the engine running you have now at least identified which cylinder it is. You can do the same method if it uses a wasted spark system with one/two coils and HT leads. Just a process of elimination.

From there you can swap the coilpacks/leads around (obviously mark them) and repeat the process. You can do the same with injectors but they're usually a ball ache to access.