2006 MCS 128K
16%, ATI Damper, Schrick Cam, Intake, DT-BPV, Exhaust.

This year has just been funky... I'll admit that because of finances I have really put maintaining my MINI aside. It seems that chicken has come home to roost.

So here's how it got started...

For the last couple of months I've felt this... intermittent hesitation, like I'd be on cruising at a steady pace and it would feel as though I was letting off the throttle just a touch when I wasn't.

I thought maybe it was a boost leak or the heat was pulling timing; I bought a DT-BPV thinking that maybe the fluctuations were being caused by a failing BPV; however I didn't install it just yet. Then one day driving home BAM.. Check Engine light and it went limp... I did a rolling restart and then it was no problem at all. So I read the code and it was a P1125. So I changed the throttle body, and while I was in there I installed the BPV. That worked, but the hesitation was still there...

So like a month goes by and then on my way to work... I lost all boost, but it was still driveable.. so I babied it home (45 miles) and then I noticed the belt was tearing apart. A bit of research and I found that the Crank Damper had a detrimental failure and so I replaced that with the ATI Damper... I figured, well... that would explain the intermittent boost/throttle fluctuation.

Nope.

So another month goes by then I get a P0456. So I thought.. well, I do absent-minded things all the time I probably didn't seal the Gas Cap well enough. That was last week...

This week, I was driving to work and then a couple blocks from home I got a CEL and my "Check Gas Cap" light was on as well. So I figured, okay.. this is probably a P0456 like last time, no biggie. I pulled over, checked the gas cap and went on my way.

So I get on the freeway and I open it up... and then I start hearing the unmistakable sound of a cylinder missing. So I immediately let off and started to pull it over... but then the cylinder came back. Either way, I babied it to the next stop. I brought it home later that night and it seemed perfectly fine... I even pushed it a couple times and it ran perfect. So I took it home and was able to check the codes and it gave me the P0455 and P0303 codes.

So I pulled the plugs... and HOLY CRAP... how my car ever started boggles the mind.





So I figured, that HAD to of been my problem...

NOPE.

When I'm cruising along, it's perfectly fine, but if I push it then I can start to feel it hesitate for power right before I lose the cylinder. When the cylinder begins to miss, I let off and I can catch it before it throws a code.

So I'm going to do a compression check tomorrow and I'm going to swap the #3 injector with another cylinder. If the missing switches cylinders to the corresponding cylinder then I know that the injection is going south.

So my question is..

1) My plug electrodes are melted at the base... I'm not sure if it's just because the top electrodes have deteriorated and the gap is too great or if I'm running too lean?

2) I hear that the MCS runs rich in the factory tune... given my mods (top of post), am I running lean due to pushing the injectors to their limits?

3) I'm sure this has been beat to death, I understand that the JCW's are choice; however, I wonder what's the highest flow injectors that can be utilized by the stock tune?

 

Injectors aren't your problem unless they are clogged which I've never seen on an R53.

I wouldn't use those plugs either as I see that all the time with the fancy iridium plugs that just fail more often. Go with good NGKs
http://www.waymotorworks.com/john-co...gs-by-ngk.html

Now if you put new plugs in and you still have the issue check the coil and wires. If they are good then compression and leakdown as you may have a cylinder problem.

Your list of mods is not enough that I would be concerned with running lean being the cause.

 

Compression Test Results

#1 - 129psi
#2 - 125psi
#3 - 127psi (The missing cylinder)
#4 - 122psi

They're all on the low side, but seem to be within tolerance. The Bentley says the minimum acceptable pressure is 136psi, so... I dunno. At 130k miles and a good beating, I don't think it's anything that would cause a misfire.

I wonder, if I am having a lower compression reading across the board due to the camshaft timing being altered by the aftermarket cam?

 

question ?? are you using oil?? plug seams dark ,, do the other plugs look similar ?? could have a bad oil ring and crank case pressure could be pushing oil up past the ring into the chamber causing misfire until you let out of the throttle and it clears up ,,, gmonde

 

Naw, they look like that because they were giving me a bit more pressure coming out than I felt comfortable with, so I shot some PB Blaster down the plug galleys to make sure I didn't mess up the threads. I just pulled my plugs today after running them for a bit this last week and they're all clean with just a tinge of white on the upper electrode which is normal.

I have some new plug wires headed my way... if it's the cause, then cool... if not, well it's about time I replaced them anyway.

I'll be swapping my injectors to try to find if the problem follows the injector, if it does then I'll replace it.

 

I'm wondering if maybe you got some bad fuel...
Some detonation...some extra heat...plugs usually take the brunt of the pinging, etc...
New plugs...some fresh 91-93 octane....see what happen...
If you burnt a valve, it might still show good compression NOW.....test will be if it is still good in a few thousand miles....
Typically, they get burnt a bit...and the valves actually change color a bit due to the metal getting altered by the temp... and get soft, then wear...
Many aviation shops have a great poster on the wall...shows a typical valve at various stages of its life...
Edit..i just read your next post with the compression tests...it is troubling that the miss is there with decent compression and new plugs...guess check wires/coil...and hope it not something worse...

 

That thought had crossed my mind... I'm often troubled by bad gas.

However, let's stick with the MINI. If I had a batch of bad fuel then it wouldn't explain the previous issues that have been on going.

I know the poster you're talking about, one of my instructors had it up on his wall over at Embry-Riddle. I know that sooner or later I'm going to have to do a tear-down, but that's not until my MINI is no longer my daily driver.

I did notice that two of my wires... one of which was #3 had dark spots where they got near to one another. I'm thinking that the insulation may of worn down and I'm getting arcing. I'm going to be more careful in the future with spacing out my wires, but there's not too much room in there.

 

Go with what Way motors said and get the NGK plugs that should be used with a JCW setup.

 

It looks like you dodged a bullet with compression. Although the numbers are low, It's probably your gauge. The important thing is that you are pretty consistent cylinder-to-cylinder. I didn't catch how long those plugs had been in your car. Long time?

 

I'm going to guesstimate and say about 40-60K miles on those plugs... it's really been a long time since I've maintained the MINI and it's catching up with me. Living paycheck-to-paycheck for awhile meant that the majority of my maintenance was saying "Please don't break, please don't break, please don't break" every time I started the car.

So here's the thing... it drives perfectly normal FOR THE MOST PART... after I clear the CEL, the next day I can drive it like nothing is wrong and it's perfectly fine as long as I drive it like a normal person. I can trigger it.. and that's what I did last night to see if it had moved cylinders.

If I get on it, Full-Throttle for a good 10-20 seconds, then it finally kicks in and stays until I clear the CEL, but it'll be more sensitive to it for the rest of the drive too...

MY TRAIN OF THOUGHT...

It's sticking with one cylinder, but it can't be a mechanical issue because I checked the compression and it's intermittent. I am thinking what if that fuel injector is dying.. and when I push it, it's basically overheating the injector and it remains hot after the initial failure for the rest of the ride.

I know that it can also be the coil, but if that was the case, would it be sticking with the same cylinder as well?

What's the next step... can either the coil or the injector be tested by me or do I just have to take the hit and try my luck with replacing either?

I'm ruling out Fuel Pressure Regulator and Fuel Pump because if either of those two failed, then it wouldn't be sticking with one cylinder each time, it would jump around. Additionally, I don't hear any additional strain from the fuel pump.

What's next?

 

So I bit the bullet and bought an injector... and as I started the car up to test it, I saw a spark jump from the coil to a vacuum line that was nearby (not electrical line) and I could see a trace of melted plastic on the #3 post of the coil.

Or COURSE it would be the other choice... but at least I know what happened.

I have a cracked coil and it was bleeding ignition spark.