Hey all, I have a perplexing issue and I am at a loss. I have a 2003 mini cooper R53 which is experiencing a sudden misfire on 3/random misfire. I picked up the car from my father who garaged it and didn't drive it all that much. It has 65k on the clock but for the last three weeks, it has been driving flawlessly. We changed the coolant, gear oil, air filter in the time he had it. I have put 2-3 tanks through the car myself.

I should start at the beginning to fill you all in. Friday I was driving to work (35 mi drive out of town) and I neglected to get gas thinking the small town I currently work in would have 91. They did not. I was in a pinch as I had to get home so I put in $20 worth of 87. I didn't think it would be an issue.

Fast forward to yesterday. I detailed the mini, drove it in the morning and when I tried to drive it later, it was missing terribly. It is no slight miss either, it will not idle without bucking and makes the car practically un-drivable. It should be noted that I there was ~1/4 tank of 87 left when it began missing. Today I pulled the plugs and indeed cylinder 3 was gassy. I regapped all the plugs, bought new spark plug wires, put in a full tank of premium with lucas fuel treatment to no avail. I also pulled the codes and got a p0300 Random/multiple misfire detected code.

Possibly unrelated, but worth a mention, the car has bubbled over the coolant overflow bottle in the recent past, but my father and I replaced the bottle as I thought it was cracked. I thought that this issue might be tied back to this as I have been unable to determine if the radiator fan is operating correctly. I have used torque on my android phone to monitor the coolant temp and it never goes over 205 F.

Any insight or experiences? I would like to rule things out before I go throwing parts at the car. The suddenness of onset of the misfire makes me think it's a fuel issue. Maybe running it low on fuel sucked up water/debris.

 

When you did the plugs did you check the connectors on the coil pack. #3 -connector ( in board on drivers side ) on the stock coil packs are known to develop patina and even corrosion causing MF.


If corroded, use green side of a scrounge, not sand paper.

 

I just tried that and it did not make a difference. The contacts looked fairly clean and bright silver.

 

Seen a bad coil pack do that too. Know any other MINI Motorers near you with either and R50 or R53 to try a swap out ?

 

I don' know any local owners so I can't swap to troubleshoot.

 

$20 worth of 87 octane.....in a nearly empty tank....ouch...
Hopefully it did not cause a burnt valve....
nuff said...but could have been a $1500 error....good luck...
Might be worth getting to a garage for a compression check...pretty easy...
Can be used to rule out or pinpoint the issue as mechanical....

 

A few gallons of 87 could really cause a burnt valve? I made sure to drive the car sensibly we going through the few gallons. I made an appointment with the local European shop, hoping for something simple.

 

Always best to go up to the next octane level...to 93....rather than down...you might want to carry a couple bottles of octane boost.... That way if you be stuck in that situation again...no worries.
Hopefully driving sensebly prevented any damage....but the fact the car started having a misfire issue RIGHT AFTER YOU USED 87 is telling.....
If the tank has been filled with high octane fuel...and still has a misfire within a few miles...kinda tells the story.
Be honest with the shop....tell them the same info.
Maybe it is a bad wire or coil...and the fill up was purely coincidental.....
I tend to look at the worst case....
Then figure out what simple cheap stuff can cause the same issue....and go from there...
A compression check is about the same labour as a sparkplug change...so minimal...and can be CHEAPER than throwing a bunch of parts at a car HOPEING it will fix it.
A coil at $75-150, wires at 50--75$, it adds up quick. Sometimes a pro is well worth the the $$.

 

I hope it is a coil/clogged injector/fuel filter/plug versus something major. There was no other option other than 87 and it was the only station. That and my state doesn't sell over 91 at the pump except for some racing fuel. I still cannot believe that 87 would so harmful in a pinch. Thanks for the input though. I'm going to pick up some dielectric grease and give that a go before dropping the car off tonight.

 

Don't panic. Putting some 87 in there while not optimum did not cause you to burn a valve. The engine has a knock sensor & will dial back ignition advance so it won't detonate. Burned valves are not caused by spark knock, holed & cracked pistons are.

You may want to do a compression test & a leak down test. This may be related to to the boiling over coolant issue. Head gasket, maybe.

Try swapping coil packs with a known good one. Don't buy an MSD or Screamin Demon.

The dealer diagnosing this problem may save you money. It costs a lot to keep throwing parts until one sticks.

 

Took it to the shop. They ruled out an ignition issue, ran a compression test and it showed low compression on cylinder 3...leak down test is pending. This is rather unsettling.

 

Turned out to be a broken valve spring. Got majorly lucky with this one as the two parts of the spring twisted together preventing the valve from being pushed into the piston. Car runs beautifully now. With that being said, is the r53 engine an interference engine?

 

No....
R53 noninterference.... Thanks to the low compression pistons...
R50 interfearance.... Due to the higher compression pistons...(pretty sure on both).

 

Very glad it was a blown head gasket or other spendy fix.