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

OK...

I'm having problems with Jango, my 2006 MCS (R53)... 6.5 years old, 80,000 miles.

Engine Mods: 16% pulley, Jan's tune, CAI, cat-back exhaust, coil-pack, plug wires, colder plugs, large intercooler

Care: I'm a maintenance freak, so the car gets oil changes every 7-9k miles. The coolant has been flushed recently, new oil pan gasket, super charger oil serviced + new serpentine belt about 8k miles ago. The battery is 2 years old or so. All of the fluids are topped-up and have remained level (no known leaks or visual signs of any problems)

I was driving home about a week ago and was 5 miles from the 80,000 mile mark on the odometer. While waiting for the roll-over event, I noticed that the DSC light was on. "Strange..." I thought. I toggled the DSC switch (sometimes I bump it on accident when rolling down the windows), but it wouldn't go off. A mile or two later, the exhaust suddenly changed note to something deeper and more rattly... uh oh. Limp mode! The SES light also kicked on. I turned off the car, restarted and drove home (exhaust note returned to normal). The limp-mode kicked in one more time in the 10 remaining miles to home.

I hooked up the diagnostic tool and got only one code: P0300 (random mis-fire).

Hypothesis #1: It's bad gas.

I was about out of gas, so I refilled at a different station that the last time (a high-volume Exxon, using 93 octane) and added a bottle of Lucas Oil's Octane Booster / Fuel Treatment to the tank. I cleared the codes and pulled away from the station.

No luck... The car went into limp mode two or three times on my 15 mile trip to and from work each day for most of a week, as it had before... OK... it's not bad fuel, unless I got 2 bad tanks in a row and the first tank didn't cause me any problems until the tank was at 95% empty.

Hypothesis #2: The coil pack was bad

Well... this wasn't my second hypothesis, but it was an easy swap, so I pulled the aftermarket coilpack I put on about 50k miles ago and replaced it with the stock unit that was working fine when I pulled it. Nope... same problems... limp mode + SES Light + DSC light.

Hypothesis #3: Bad plugs and/or bad plug wires
This was really my hypothesis #2, but it takes a bit longer to do the swap, so I just got around to it this weekend. I pulled the plugs (NGK that are 1 degree colder) and plug wires (quality aftermarket wires) and replaced 'em with a set of Brisk plugs that I pulled off of the car a while ago (they were working fine when I replaced them proactively after 30k miles or so) and the stock wires that only had 30k miles on 'em. I cleared the code and went out on a test drive.

Ugh... same problems. I really thought this was going to fix it!

3 of the plugs (1,2 and 3) looked the same on the business end... some light rusting but basically dry all around. #4 (driver's side) was the only one that stood out as being slightly different, but nothing so out of the ordinary that it would have normally worried me (and #4 has always been a bit different when I've pulled the plugs over the last 6.5 years). The plug on the left is from 1, 2 or 3. The plug on the right is the one from #4.



Hypothesis #4: ???

This is where I am right now. I've got a few ideas, but I'm looking for any help someone wishes to offer.

1. Perhaps a vac leak or maybe my supercharger boots are leaking. When I swapped the plugs, the supercharger boots (silicone Alta units) looked a bit worn out and chewed up. Maybe I'll get some fresh ones sent out as they probably need to be refreshed anyway.

2. On an R56, this code in isolation is a symptom of a high-pressure fuel pump going out, but I haven't heard of that issue in an R53. I haven't changed the fuel filter in 50k miles or so, but people frequently NEVER change them on the R53 with no problems.

3. Again, on an R56, this code can be a symptom of carbon build-up. I haven't spotted this issue on an R53 thread, though, with this same code. Possibly a bad valve, maybe (spotted this on one thread somewhere that a bad valve caused this same code)?

4. Still water in the fuel? Maybe I need to add some Sta-bil fuel drier and push another tank of gas through the car.

5. O2 sensors? They tend to die around 100k+ and I'm at 80k now... possible?

4. Any other thoughts?

Thanks all!

 

I remember throwing a SES light back when the car was under warranty (don't know what code). I had put on the intercooler only 3-4 months earlier and was using the stock boots. My dealership replaced the throttle body under warranty but politely suggested that the poor fit of the stock boots w/ the GMRS intercooler could have also been the culprit and suggested a heavier aftermarket boot should be applied. I ordered the Alta boots when I got home and put 'em on a week later. The code never came back.

New Alta silicone boots are on the way, as is a new fuel filter (it's time anyway and it won't hurt to get a good look in there and see what's up).

 

Strange things afoot this morning...

- I found about 1/4 cup of coolant on the garage floor (may be un-related as I topped up the coolant earlier last week). I had noticed some spotting under there over the week, but it's summer here in TX... I had marked it up as AC condensation drippage. This was definately sweet blue coolant, though.

- right after I swapped the plugs and wires, I took the car out for a test drive. It went into limp mode about 1/4 mile from the house. I let it sit overnight and then drove 20+ miles to the office this morning without a hiccup!

 

I'm liking the idea of that homemade boost leak tester. I can't see the pics from the office, but I think I can rig something like that up, especially given my DDM intake.

 

Hmmm... well, it went into limp mode again as I drove off to lunch.

I think I've got another set of injectors on the shelf (the stock MCS pieces... I'm running JCW injectors w/ Jan's tune right now). Would it be worth swapping these back in for diagnosis? Would I run a risk of going too lean (just for daily driving... not going to the track like this).

On the overheating front, I've never seen the temp gauge go above normal and I've been keeping a close eye on it with the 100+ degree temps we are seeing and the code being thrown regularly. Is there a gasket failure or cracked block explanation that might tie the P0300 code and the coolant leak together?

Looks like I'll be under the car this evening, trying to see where that coolant leak is coming from.

 

I crawled under the car to get a good look when I got home tonight. Coolant was dripping off of the front edge of the oil pan fairly quickly (2-3 drops in 10 sec). I couldn't see a source from the hoses, thermostat or radiator... Maybe the water pump or the flanges that lead to it.

Unfortunately, i don't have time to deal with this right now. Will probably break down and call the dealer tomorrow.

 

Yep... poor Jango is at MINI of Dallas now. I hate taking him in, but I just don't have the time to go digging (even if I had the requisite skills or knowledge) anymore and I don't want to risk possible damage from continuing on myself.

 

Well... one bullet dodged and one still in the air.

The leaking coolant was from bad shaft seals on the waterpump... the one that I bought new from MINI last fall (and is still under warranty, as is the labor to replace the defective part). Yea for the compulsive receipt keeper! That was gonna be an expensive fix.

The dealership wants to fix the coolant leak and then diagnose the P0300 issue. Will see what happens on that front next.

 

I dropped by the dealership this morning to flash the original receipt. They already had the waterpump work scheduled for today, so I might hear something on the misfire issue tomorrow morning.

I'm always leery of having service done at the dealership, but so far it has been a pretty good experience... they got me in for diagnosis the same day that I called 'em and happily took the warranty work on the water pump once I emailed in a scan of the receipt. Keep it up, MINI of Dallas!

 

OK... just heard back from the dealership. They fixed the water pump under the part warranty. They then checked the codes and couldn't find any evidence of the misfire (except for the P300 code in the memory). They drove it over 15 miles (and it should have done it at least once if not 2-3 times given my recent history), so perhaps the water pump problem was somehow causing the misfire issue. Either that or the Techron I added to the gas tank just took a couple of extra days to clean the injectors.

They mentioned that the foam airfilter appeared to be over-oiled, but I haven't touched that for over 6 months, so I seriously doubt that is the issue. I'll give it a cleaning this weekend, just to be safe. Hopefully my new supercharger boots will be here, so I can update those, put in the new fuel filter, replace the performance coil/wires/plugs and get Jango back to normal!

Jango is ready to be picked up and there is no bill due for the service! I'll owe a bit to Enterprise for the loaner while they were working on the car (EDIT: Nope... MINI covered the rental as well! Total bill = $0), but in the grand scheme of things, it all looks good!

Thank you for the professional and attentive service, MOD (MINI of Dallas)!