smoore100

Hi all

I picked up my car a week ago, and this morning did my first decent journey - around 100 miles.

All week I'd though that a slow speeds the car was a little hesitant and perhaps a bit 'rough' but as I was only driving a couple of miles to the train station I didn't really get chance to do some decent miles until today.

Under acceleration, it definitely doesn't feel right, almost like a misfire - but when up to 40+ mph everything felt fine, especially when cruising on the motorway.

As I was getting close to home the Check Engine light came on, and has stayed on, After reading through as much on the internet as I could find, it sounds like the ignition coil(s) could be shot, and after checking through the history they don't ever appear to have been replaced, and the car has now done 90k.

Ill' be going back to the garage tomorrow but am keen to find out if my - totally amateurish - sounds about right so I know what to expect.

Any ideas?

Regards,

Simon

nodoors

Sounds likely, but impossible to say for sure. You should definitely replace the plugs and might as well do the coils while you are in there. Baseline the all fluids too if you want to keep it running well for a while. Get one of the code scanner options that people talk about on here if you are going to be doing the work on the car. It will tell you if it is definitely the coils and definitely be helpful with service and the next problems that are waiting to pounce on you.

smoore100

Hi

Thanks for the reply, I just spoke to the guy who owns the garage, they are not open today but I'm taking the car to the workshop tomorrow. His first thoughts are coils, the plugs were changed when it was serviced a week or so ago.

I think he has a diagnostic tool, if not it appears that if a coil has gone - a visual inspection should identify that?

Thanks,

Simon

nodoors

The best way is a code scan that shows which cylinder is misfiring. If you are taking it to a professional then, hopefully he will start by looking at the codes.

smoore100

Yes he hooked it up to a diagnostic tool, misfire on cylinder 5 - coil pack ordered and will be fitted in next couple of days

nodoors

Might as well do them all as the others will likely be soon to follow, unless you like getting stranded or washing your cylinder walls.

smoore100

Yep - that's what he is doing this week.

Cheers,

Simon

oldskewel

EDIT - on re-reading, I see the spark plugs were replaced last week. Correct ones, I hope. And I hope they really did replace them - you never know, sometimes. Given that, it seems odd that they would have the coils in hand (to remove the plugs) and not notice any cracks. Having someone else do the work adds a lot of complexity to the analysis. Good luck.

(so the rest of this is my original comment, which would apply if the plugs had not been changed already. Some still applies)

If spark plugs are due, you'll be right there to replace them.
And hey, once there, may as well throw a compression gauge on there.
And borescope the cylinder.
For all 8 cylinders.

I'm only kind of kidding. If you can do it yourself, that would definitely be wise to do. I did all of that as my own PPI when I bought my 2004s and there was a weird engine noise and I got bit by the cylinder scoring paranoia bug (still not cured, BTW).

The most "challenging" (not hard, but just a little different, and requires some finesse and being careful and patient) part of all of the above was just removing all the plastic stuff and torque bar (if you don't have the M12 triple square socket handy). Once all that is off, the coils + plugs are right there.

As far as visually checking the coils, mine were all fine, but from seeing pics on this site, apparently what happens is they crack longitudinally and that leads to arcing and misfires. So yes, once you pull the coil, you might see a nice long crack in it and would then know it needs replacing and is perhaps the problem.

Also, you should check the part number stamped on the coils. They continue to be revised. The first version was probably .00. On my 2004, which had all new coils on in 2009 when the engine was replaced (!!!), 6 of them ended in ".03" and 2 ended in ".05". I think they may be up to like ".21" or something like that by now. So if nothing else, the part number on there might tell you how old the coils are, which I know might be tough if you don't have complete and accurate service records.