Regular readers may remember that the Sheds have two grown-up children, Garden and Potting. Mrs Shed wanted more children but it didn't happen. There was a nasty moment in the garage when she stormed in to blame her husband for this failure to procreate. Shed was hidden from view under the bonnet of a misfiring M54 BMW at the time. He was on his mobile to the BMW's owner. Unfortunately, all Mrs Shed heard by way of a response to her accusatory shouts was 'it's probably a coil problem'. He's still got a scar showing exactly where the bonnet edge came down on the back of his head.
Like Shed (allegedly), this week's temptingly priced BMW X3 2.5 has a misfire. And just like the M54 that Shed was fettling back then, it's probably a coil problem. Coil removal and installation time depends on where the faulty one is located, but even if the fault code tells you it's number six at the back you should still be able to get it done in under half an hour without too much faff. The only tools you'll need are a screwdriver to prise up the valve cover retaining bolt caps and a 10mm socket to remove the cover bolts. Snap back the coil retaining bracket, heave out the offending coil, ram in a new one in and hey presto! A fully functioning six-cylinder X3.
Maybe. It might be more than one coil that's faulty, or it might be something else altogether (read on). Sticking with the coils for now, if one's gone there's a fair chance that the others aren't going to be in the best of health, so it makes some kind of sense to replace all six of the blighters while you're in there. New Bosch coils for the M54 are under £50 each, or you could take a chance on secondhand ones for half the money.
Then, assuming it's not something else that's causing the misfire like faulty plugs or something else we'll talk about in a minute, what will you have? A car that's generally acknowledged to be the first midsize premium SUV. With an all-wheel drive system defaulting to a 40/60 front/rear torque split and the facility to direct all the torque to the back axle, the 2.5 had 189hp at 6,000rpm and 181lb ft at 3,500rpm. Despite those decent numbers, the auto was too weighty at 1,840kg to be massively fast. Its 0-62mph time just about made it into single figures and you wouldn't be entering too many economy runs in one either (do they have those any more?) because the official combined fuel consumption was only 23.7mpg. The suspension seemed a bit hard at the time too, though it probably wouldn't now.
A six-pot X3 was premium, however, and could still be a nice thing to smoke around in even now. The chain-timed M54 was a reliable motor as long as you put some maintenance its way. Switched-on owners liked to double the frequency of oil changes to 7,500 miles from the recommended 15,000. They wouldn't neglect coolant refreshes either. If you followed that sort of schedule you could easily get your M54 over the 300,000 mile mark.
You'd need to keep an eye out for other problems though. Gaskets for oil filter housings, valve covers and sumps are well known weak points on these engines, as are crankcase vent valves. If changing the coils doesn't pinpoint the misfire, a fault with the CCV might. Poor access makes replacement difficult but much easier and cheaper DIY solutions have been devised.
A broken DISA (Differential Intake System) valve is another potential M54 ailment. This system altered the effective length of the intake manifold to improve running under partial or full loads. A loud rattle from the intake and weakened performance are the giveaways to a busted one. Water pumps go too, but that's hardly BMW-exclusive.
As Shed was researching this X3, he noticed a very similar one on a well-known auction site. Not a Sport like our one, so somewhat more austere in the cabin department with flat rather than bolstered seats, but the same colour, same year, same 130,000-ish mileage, and holding a clean MOT to next July. At the time of writing with more than two days left, the healthy bidding on that non-Sport X3 2.5 had already topped £900. Our shed is £1,189, or just under £1,500 if you replaced all the coils yourself with new ones.
The only advisories on its fresh MOT are for a non-excessive oil leak (check those gaskets), a minor exhaust blow, and some light misting on the offside front damper. These issues wouldn't put Shed off this sensibly sized all-wheel driver, especially with winter - and a perpetually angry Mrs Shed - fast approaching.
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