1st Gen R53 Cooper S P0300 Error (random mis-fire) and limp mode

Oh yeah... I'll try to remember to pop back on this thread in a week or so to let you know if the misfire is really gone.

 

I made it home last night and all the way to the office this morning (30+ miles) without throwing another code, so it looks like things are back to normal.

I've got a new fuel filter, intercooler boots and a tensioner stop ready to go in to the car this weekend. I'll put the aftermarket coil, plugs and wires back in as well.

Given the 2 year parts warranty from MINI on the new waterpump that went in last fall, MINI picked up the tab on the new water pump, the labor for the replacement (10 hours, I think) and my 3 days of rental on the Corolla. I would have rather had a good pump sold to me last year, but at least I didn't have to pay the $1400+ on the repair. Very nice! Sometimes crap happens and it's nice to know that MINI stands behind its parts.

MINI of Dallas gave great service and called me regularly (SA = Joe, but I got some help from James who was also very friendly and helpful). They diagnosed the water pump on the same day that I first contacted 'em and had the car fixed one and a half business days later (with a 10 book-hour job to be done + diagnosing / checking the misfire code), so I couldn't have asked for much more.

 

I have NO idea how a bad water pump (especially one that was leaking, but was still functioning well enough that the car never overheated to the point that the temp gauge ever went above normal) could cause a random mis-fire code. I think it was more code than mis-fire, because I never felt or heard anything strange with the engine until it went into limp mode. It pulled strong and felt like my normal drive.

My theories:

1) The Techron I added to the fuel tank finally cleared out a fuel injector while it sat in the shop for a few days
2) In the process of replacing the water pump, they tech shored up a flaky electrical connection
3) The engine was getting hot, but not hot enough to overheat. The heat caused some strange thing to happen that was causing the code. Now that more coolant is circulating, the issue is solved.

The old wires/plugs/coil pack went back on this morning, along with a new pair of Alta intercooler boots (I HATE those things the first time you try to put 'em on the car) and a new fuel filter (I ordered it and it has been 40k miles or more, so why not).

The car has driven like a champ for the past 2 days... no codes and no issues in about 50 miles.

 

2 more days and no issues... not a single drop of fluid of any sort on the garage floor and no codes/limp mode. I'm calling this one fixed.

I mangled a gasket when re-installing the fuel filter, so I had an air leak and I got the 'check fuel cap' light a few miles after that change, but they give you 2 gaskets in the box, so I reinstalled with a fresh one and everything is good. Woo Hoo! It's nice to have Jango back to normal and worry free. There is nothing like driving a crappy rental car for a few days to make you realize how much you love the MINI!

My hands are even healing from the hour-long struggle to get those f-ing intercooler boots on the car. I would have gone back to stock, but I've got an early GMRS intercooler and the shape of the intake/outlet isn't a great match for the stock boots... the thickness of the Alta boots allows for a bit more play.