Help needed - stuttering/stall
 

MINI HELP NEEDED (R56 N12)

Hello,

I found a decent price on fuel injectors from a well reviewed (forums) supplier so I'm throwing money at '10 non-S with constant stuttering/stall problems.

Background: car was given to me by a family member because they bought a new car and know I'm willing to work on this one. (I have two Land Rovers-sucker for punishment). Mini had/has 63k/65k miles.

Repair list: (completed)

Upon arrival to my house-
Thermostat housing assy (leaking)
Water pipe (good time to do it)
Water pump (good time to do it)
Coolant

Fortunately my family member is older and never paid attention to mini book or dealer and did oil changes annually (5000-7000mi/yr). (See timing checks below)

However, shortly after receiving the car and the coolant leak repairs, some issues arose. At first, just some hesitation during accelerator release/no load. But then after a couple of keep weeks of that with no codes and gradual worsening, the car started throwing codes.... 2178 and 5 misfire codes - 0300,0301,0302,0303,0304. So I decided a tune up of sorts was in order after reviewing maintenance history with family member and doing a bit of research here and other places. I pulled the plugs and although not terrible, not great since last change 2k miles prior. Oil was also very dark for 2k mi. prior also.

Before the following, I ran techron grey bottle fuel injector cleaner.

Air filter
Fuel filter
Oil filter/oil
Spark plugs
Intake manifold gaskets
Valve cover (cyl2 had recently started a leak - very small, hadn't even reached the plug yet. And the pcv was fairly dirty so I just replaced the whole thing).

During this time I checked the timing chain, guide and tensioner and all appear to be fine - visual and manual check, I don't have special tools beyond that. I also pulled both Vanos and they looked great, in fact brand new although I can't find any history of being replaced.

Car ran great for about two weeks, only to have codes return. No misfire codes but 2178 (again), and now 2196 and 0420 for the first time.

Repairs I've ordered parts for:

So now I ordered two O2 sensors (ntk) and 4 injectors (vdo), they are on the way. Cheap enough and from what I've read total possibilities. I'm thinking worth doing at this point because they could be fouled based on rich condition during running and how the fuel filter looked and the gas previous owner may have been using was any gas station they passed, lowest price. I know, I know. Carbon build up etc.

For the record:

So far, not counting other incidental costs, wipers, two older/mismatched tires etc. - just the motor stuff, I'm into a free car for around $800 or so. Not too bad for a free car but I'm still chasing the codes. Also, for the record, on a car like this (it's not a beater), I don't skimp on parts. I buy the correct recommended parts, oem, vdo, ntk etc. or other as each case recommends based on my reading, surveying shops, talking to other owners and so on. I don't buy the cheapest just to save money. I look for the right part and try to find the cheapest price online and so far, have done all the work myself so I save a lot that way.

But...

WHAT ELSE COULD BE CAUSING THIS PROBLEM?

Very last on the list because of cost, is walnut blast if injectors and O2 sensors don't fix.

Car doesn't seem to leak or burn oil or any other fluid for that matter. Exhaust smells very sweet but expected during rich condition. Beyond that, and the codes that keep returning, there are no other symptoms. Not even the gas mileage has gone down as long I keep clearing the codes.

ANY legitimate HELP is much appreciated in advance. Thanks!!!

P.s. If I can't fix this soon....I heard RS6 is coming stateside so I'll switch back to Audi. :P

It doesn't look like you have done the ignition coils yet. I would definitely replace all four of those. From reading on here and elsewhere, it seems the coils on these cars can last from 25k to 100k miles. And, it seems that the coils often just get weak rather than go completely bad.

My 2013 has 45k miles and had hesitation on acceleration but no codes. I did the plugs with no change. Then I did the coils and it was night and day difference. I got a set of the Bosch coils from ECS.

Just a suggestion.

The coils look really good. No wear, no degradation of the rubber, no dirt to speak of. Even the plug top is in perfect condition. And after the misfire codes went away, seemed like a non issue.

Any way to bench test them without doing cylinder swap since no cylinders are misfiring?

I checked some pricing, they seem pretty cheap to do as well I just never considered because they look so good inside.

I haven't ever heard of coils/coil packs doing a stutter then driving fine. It's usually either good or no good, they don't "warm up" or respond better to different driving conditions based on age/wear do they?

I too have always seen coils just go bad and no longer function. But, again mine wasn't setting any codes but at least one coil was definitely bad.

Do a search on here. I'm pretty sure that others have found the Delphi coils not to be any good. This is why I got the Bosch from ECS. If I were in your shoes I would simply buy a good set of coils and replace them as preventative maintenance. But, it's quite possible it will solve the issue. Who knows.

Otherwise you can take it to a Mini dealer and have it diagnosed by a professional who can see and test things in person.

Is this a symptom?

When the tank is full, it doesn't stutter at all. As the gas tank gets lower and lower, it consistently gets worse.

I did not see this symptom listed in your original post. Sounds like it's time to take it to a Mini dealer or independent Mini expert shop to diagnose. Or, just go back to an Audi.

It wasn't in the original post. I don't really drive this car. This is something my wife mentioned yesterday now that she knows the issue and has been paying closer attention.

Just an idea:
Try taking the gas cap off to let some air into the tank & see if the stutter goes away for a while.
I'm thinking there's a blockage or leakage in the tank ventilation system (EVAP?), but I'm not sure how it's supposed to work.