Bought a MINI - couple of niggles

[mnkiboy]

My girlfried purchased a MINI Cooper over the weekend. It's a 52 plate on 74k miles.

On the test drive all seemed fine, but having got it home and taken it out for a few drives, it seems it has a low speed misfire. Under load, below 2000rpm it tends to cough and misfire slightly. Above around 2000rpm it's fine.
Had a quick search on the net for similar symptoms but couldn't really find anything. I haven't had chance to replace plugs and / or coil pack yet but that's where i'll start unless anyone can suggest anything else. Seems strange to me that it only does it at low speeds.

The car also seems to have the thermostat stuck open, as the temp drops as speed builds. Not sure if the two issues are linked.
Slightly more worrying is that the coolant level was low. I've topped it up and will keep a close eye on it over the next few days.

Otherwise the car drives very nicely, and you wouldn't guess you were sat in a 10 year old small car.

[mnkiboy]

The dealer stamped the service book to say they've given it an 'Inspection 2' service. I doubt this, but it has had a new air filter. Not sure on plugs but i'll pull them out and check them this week if I can.

Is it one single coil pack on the MINI or one for each plug?

[Dave^]

It's a single coil pack on these...

The part numbers match for a few different cars, Chryslers in particular, so it's worth hunting round make sure you avoid BMW tax...


eta - http://www.ebay.co.uk/itm/ERA-Ignition-Coil-MINI-M...

It's worth doing plugs/leads/coils in one go, for piece of mind as much as anything else... if everything's still original, how long will they last?

Edited by Dave^ on Monday 5th November 11:31

[MX-5 Lazza]

I'd replace plugs & leads first. Low rev misfire sounds like leads to me. No need to replace the coil pack if you don't need to. Fitting new plugs & leads will not cause a problem for an old coil pack. Replacing a coil pack without fitting new plugs and leads however is a bad idea as it's often high resistance from failing leads that cause coil failures.

[mnkiboy]

Thanks guys, i'll try plugs and leads first then take it from there.

[Dave^]

Most of the guys over on minitorque change the coilpack every few years as part of the service.

Don't be tempted by aftermarket ones either...

http://www.minitorque.com/forum/f845/what-coil-pac...


Loads of advice on minitorque, although they are...erm... to the point, shall we say. They are very knowledgeable though...

[ging84]

should not need to replace the coil pack, you will often find that one or more of the terminals has suffered corrosion, often seems to be terminal 3 (no one know why that one specifically) you should be able to do a bit of sanding on the affected terminals and good as new, i found when i did it i had to replace the leads, possibly the corrosion had transferred to the inside of the lead

[JamesK]

I had the misfire symptoms you describe on my JCW - got worked up reading all the things it could be but it was plug lead breaking down (No 2 I think). Definitely check this first.

[mnkiboy]

Thanks, will do. I tend to have a habit of jumping in at the deep end and swapping everything, instead of starting with the simple stuff.

[Cerbieherts]

Had this exact fault on the wife's '01 cooper. I replaced plugs and leads and substituted a good coil to no avail.. There was a P0303 code stored and after a couple hundred more miles if you left it idling the engine light would come on. A compression test revealed cylinder 3 was down to 60 psi, it had a burnt exhaust valve. If you have just bought the car I'd get in touch with whoever sold it, they may have been aware of the issue.

[mnkiboy]

Finally got round to taking a look at it this weekend. Removed the old coil pack and immediately found that the existing bolts holding it down have metal 'sleeves', which wouldn't fit in to the bolt holes in the new coil pack. I did though notice that terminals 2 and 3 of the old coil pack were very rusted. After a rub down with a pit of sandpaper and a metal file, and the addition of new HT leads it's performing perfectly and the mis-fire is cured.

2nd job was to replace the thermostat. To get at the thermostat the battery tray needs to be removed, but it seems the bolts holing the tray on have stripped their threads, as the bolts turn but don't realease. I've tried drilling them out but can't shift them. Going to consult the local garage this morning to see if they can do anything with it.

1 out of 2 isn't too bad I guess.