Quick background:
2011 MCS w/ 37k miles.
Accelerated pretty hardly today (not pedal to the floor but hard regardless) aaaand:
- Experienced SEVERE cut in power
- CEL came on (P0300, P0301, etc.)
- Car now stutters from 1-2k in any gear

Some other info:
- JB+ installed
- CAI installed (K&N oiled type)
- Techron added to most recent fillup of 93 octane.

Steps I've taken so far:
- Pulled the JB+ to see if it was causing it to run too lean.
- Cleared the codes, they came back but different...all still P03xx types.
- Filled up the remainder of my tank (was at roughly 3/8 tank) to rule out bad batch of gas and/or Techron causing issues.
- Cleared codes again, they came back but again came back randomly but all same type (P03xx).


My thoughts:
- Will be running to the local auto store to grab a can of CRC to clean the MAF...could it have gotten some oil on it from the air filter during the hard accel?
- I've disconnected the battery and will check in the morning to see if the ECU was still having a fit because it needs a reset.
- Should I throw the stock airbox in?
- Being that the CEL's are all being thrown randomly but still of the same type leads me to believe it's running too lean.

Thanks in advance for any help, I'm not TOO worried but it is worrisome.

 

Use the proper MAF cleaner. You may have some oil from the K&N contaminating your MAF, but the wrong cleaner will kill it for sure. I am not gonna say HPFP, but....my symptoms when the HPFP was going out was misfiring/almost stalling then recovering when started cold. Then started misfiring/bucking/cutting out under acceleration. Then half check engine light, and limp-home mode, no turbo. Pulled multiple misfire codes, and low fuel pressure codes. My HPFP was covered just a few days before my factory warranty ran out. Good luck! Let us know what develops, please.

 

The odd thing to me is that it was SO sudden. No symptoms before, no trouble cranking or almost stalling after cold start...literally nothing.

 

if you think its the MAF have you tried unplugging it? the computer should load default settings for it that should eliminate the stutter
im only going by a couple other posts i saw here and some other forums where they installed CAI and had similar issues, stopped when they unhooked the MAF

 

I haven't unplugged, left it unplugged and turned on the car. I have however unplugged it from the JB+ and reconnected it as it is stock. I would think that would be enough to "reset" whatever the ECU was seeing.

 

Unplugged MAF, ran no better, plugged back in.
Now getting P0303 code (misfire on cylinder 3), having a hard time cranking/sputtering when turning on pretty drastically.

Now I'm beginning to worry.

 

You are dealing with misfire across multiple cylinders.
Start by inspecting the sparks and coils - are they clean? Oil soaked? Consistently across all 4, or some stand out?

If one is particularly suspect, clean or replace it, and reset the codes.
Take it for a test drive.
If codes return, write down which cylinders are misfiring, move the plugs/coils between good and suspect ones. Repeat. See if the codes move with the suspect plugs/coils. If they do, replace the suspect parts.

While poking around the engine bay, double check that your air intake pipes are properly connected. If you were swapping air intakes recently, and one of the clamps may be loose.

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If one does happen to be dirty what would you recommend cleaning with? Anything household? I don't have anything on hand other than basic household stuff and no access to another car for a few hours.

I'm currently working on finding my socket set to check the coils/plugs..girlfriend just went berserk on a cleaning spree and now I can't find anything. Perfect timing.

 

Checking the coils won't require much in terms of tools - other than a torx to remove the cover over the coils? For cleaning I would not use anything harsh or with bleach or ammonia. Maybe some ammonia free windex would be mild enough. I just had random misfires on my 2012 justa and I moved to coils to see if the codes went with them. Oddly enough the misfires did not come back and now my car is running fine. So strange but I'll be keeping an eye on it. I had the same problem in that this came up after hard acceleration while entering traffic on a right turn.

 

Just got done swapping coils and checking the spark plugs - swapped 3 & 4 and checked both plugs. The plugs appear to be pretty fouled up which seems odd for such low mileage on them (JR: tools were for the plugs).

Didn't think to take pictures but both were very dark black on the tips but not down through the threading like you commonly see. Looked somewhat like the one on the left in this picture I found.

I'm replacing them as soon as possible regardless of this being the root cause of my misfires.

Edit: there is also a smell of gas leading me to believe that the trouble cylinder(s) isn't igniting the gas properly. Also makes me think the plugs could be the issue.

 

Sorry for hammering this thread but some things just came to mind:

On my second most recent tank of gas I gave it a shot of Techron. Now I know the opinion on some on fuel additives is somewhat akin to that of snake oil BUT, being that Techron is supposed to clean carbon, could it have, in any way, caused carbon to build up on the spark plugs?

Secondly, the JB+ changes fuel/air ratio if I remember correctly. Has anyone else had issues with the JB+ and running too rich?

 

The JB+ will make you run slightly lean not rich.

 

I had the same behavior on my '07 when it had the alta flash. It turned out to be carbon buildup. Valves were covered and spark plugs were nasty too.

I don't know if the tube accelerated the carbon buildup but I uninstalled it after that.

 

I know carbon was a major issue with the N14 but from what I've read the N18 shouldn't be nearly as bad or an issue at all.

So what was the resolution? Walnut blast? And when you say you uninstalled after that do you mean your tune?

 

Your right on the 14 v 18. Not sure about the N18. Yeah I had to have the walnut blast then it was back to normal. After that the chain tensioner failed causing my pistons to smack valves.

 

it sounds like you just need some plugs, are you getting a hard miss or only on hard acceleration? hate to say it but mini uses some sh*tty plugs and they don't last very long. my n18 with jb+ plus only lasted 35k miles and had misfires.

 

It all started from a hard acceleration and now am always receiving misfires. Unfortunately I have no way of getting to local auto store til tomorrow without taking the Cooper which I'd rather avoid.

 

drive the car hard and see if you can get it to have a hard misfire (where the engine has a dead cylinder) if you can get it to hard misfire then one of your coils are faulty and with the engine on and car parked you can pull the connectors one at a time to the coils to find which coil is faulty. if you can not get it to have a hard misfire then i would say you just have bad plugs and will need to replace them. its not uncommon with the minis to go through spark plugs fast. JCW are supposed to change them every 36k and the cooper s every 50k but they never last that long

 

by the way that picture of the plugs look it looks like that cylinder with the plug that s darker than the rest may have a faulty coil. id go for a drive, do 40mph put the car in 6th then petal to the floor, this will normally get the car to have a hard misfire.

 

I did try earlier today to drive it fairly hard for that exact reason but it just cuts power and doesn't appear to hard misfire like you're describing. I swapped the coils earlier but it's throwing CELs pretty randomly and doesn't follow the coil. I didn't check the plugs for cylinder 1&2 but did on 3&4 and they were both pretty black/sooty so I'm assuming 1&2 are also.

I'm planning on getting new plugs regardless so we'll see tomorrow what they look like when I go to replace them.

It's very curious to me that this happened on the tank of gas I added Techron to without having any prior issues or symptoms.

 

its not uncommon, my car did the same thing, was running fine then one day i was going for a cruise and it started to misfire on hard acceleration and it was all four plugs around same mileage. its most likely just the plugs if you couldn't get it to hard miss

 

Thanks for the info, it's calmed my nerves a little for now. I've got email notifications for replies to the thread that I've been on top of ALL day haha.

Fingers crossed and I'll update tomorrow with any developments. Out of curiosity, what brand plugs did you replace with? I'm in a bind so I'm going to have to settle for Denso brand plugs as that's all Advance Auto Parts carries (nearest store open Sunday).

 

no problem, i actually had mine replaced with oem ones since it was under warranty at that time, i have put about 25k miles on since the plugs with no further misfires

 

I would stick with the OEM or NGK. People have report issues with the Denso.

 

Only issues I'm hitting is the availability of those brands locally. I've checked Advanced, O'Reilly, AutoZone, Walmart, and none have them. I absolutely have to have the car for Monday as it's my only transportation and have a rather important appointment (awesome timing, eh?).

Oh and the local Mini dealership is closed Sunday..nobody at the cash register to check me out even if they set them aside today. This could get interesting.


Edit: luckily the ONLY PepBoys locally has 4 NGK in stock. It's the only store in 75 miles...wtf!?