2005 R53, stock/no mods:

Turn the key to start the car and it feels like a struggle/hesitation to turn over. It does start every time - sometimes during idle it stutters here and there but it’s never consistent.

Do I start with spark plugs? Coil pack? Plugs? Get the whole ignition set from ECS and cancel out anything possible instead of chasing it?

Currently no codes or lights on. Car seems healthy otherwise and drives fine.

 

No you don't start with parts; you start with a proper diagnostic with a qualified mechanic. Typically a good tech will charge 1 hour for the diagnostic and will tell you if he/she needs more time. Throwing parts at it is not the answer. If you want to do the repair work yourself, just let the tech know you only want the diagnostic.

On the other hand; you failed to tell us if the engine is current with the recommended maintenance schedule. It amazes me how people neglect to perform routine maintenance and then wonder why the engine is running like C&@%.

 

Well I asked bc the two shops I took it to (reputable euro/mini shop, other was MINI dealer) could not diagnose the exact problem. It’s intermittent and didn’t happen of course when I got there.

Smoke test showed no leaks and diagnostics came back fine so now I am here.

Edit: forgot to add that while it was a one owner car and has “records” (handwritten of when gas was even purchased) all it says is service done so I can’t tell what was actually done. Kind of why I ask if I should just do the entire ignition service kit/tune up and see if that solves it.

 

I find it hard to believe they didn't but did the two shops check the battery and/or alternator, both static and running?

 

Battery is new and was replaced by the dealer I bought the car from 2 months ago but I’ll need to check the report to see if it was checked.

 

Understand ... intermittent problems are a PITA to fix sometimes. How many miles are on the engine?

Based on my experience with VVT (VANOS) engines and your description of your problem, I'd be looking at the VANOS solenoids first.

There are some easy diagnostic checks you can perform to rule out some things. For example. What happens if you floor it? Does the engine hesitate under WOT or does it run strong (trying to rule out the fuel pump here). If the engine struggles under WOT, then you should put a gauge on the fuel rail and check the fuel pressure.

Another test you can perform while the engine is misbehaving is to disconnect either the inlet or exhaust camshaft sensors. This will put the engine in a sort of "secondary mode" operation; the DME will drive the eccentric shaft to full valve lift (approx 171 degrees), and take the eccentric shaft and VANOS out of the picture; the throttle body will be in command of air flow to the cylinders instead of controlling airflow via the eccentric shaft motor. If the hesitation goes away with the sensor disconnected, you can focus on your VANOS solenoids or eccentric shaft motor.

Lastly, you can connect an inexpensive scan tool under the OBDII menu (not the MINI menu) and look up your short term (ST) and long term (LT) fuel trims. Record the numbers at idle, 1500 rpm, and 3000 RPM. Post your numbers. Fuel trims should be near zero for a perfectly running engine. Anything over 10 or less than -10 indicates a problem is brewing.

Oops for got to mention the O2 sensors. My sister-in laws 2013 MINI had a similar problem to yours; it turned out to be her upstream O2 sensor. With your diagnostic tool (also under the OBDII menu), pull up the upstream O2 sensor CURRENT. We're not looking for voltage because your upstream sensor is a wide-band sensor. monitor the sensor current while adding propane to the air intake duct; while adding propane; the current should drop and flatline until you remove the propane; when you remove the propane, the current should rise. In my sister-in-law's case; she had no code for a faulty upstream sensor, but by performing the propane check I was able to see the upstream sensor was not responding. I changed it out and her sluggish idle problem went away. Her fuel trims were way off too, but those corrected as soon as I changed her upstream O2 sensor.

 

very familiar with Vanos as majority of my last vehicles were BMW, especially the E46 M
BUT - I was almost certain the R53 does not have Vanos? I could be wrong.

Car has 70k miles and as originally mentioned, car drives fine. No other issues, pulls fine, no oil leaks (shocker) etc etc. it’s just this intermittent thing of struggling to turn over completely on start up.

 

So are you saying it doesn't crank over properly? As in a starter or electrical problem? Does it make a partial revolution and stop, or something similar? Or is this a problem after the motor is running?

 

Yes that’s what it’s seeming like. No problem after motor is running.

BUT… just went to check my battery posts/connectors and positive side was more than half way off the post.

Pushed it all the way on, tightened it and got a good”normal” start. I’ll keep an eye on it but next step is to go get the battery and alternator checked and tested to make sure it’s getting a charge.

 

Bet you've found the problem, good job! How did the other two shops miss that?

 

That’s the hope but I’m still gonna keep an eye on it for a couple of weeks and make sure before I start throwing parts at it.

Not sure about the shops but I still want to get the battery and all that tested since who knows how long it’s been like that - I have only had the car since April.

 

Good input @slofut - Right or wrong you beat me to it.
That would've been my initial suspicion. As well as checking the grounds... and heaven forbid - inspecting the condition of the positive connection to the starter (it appears to be difficult to get to).

Chasing down electrical issues suck!

@Alkaidovich I hope that was the solution to the problem so you can resume happily motoring on.
- Best of luck!

 

Update:

Went to run a quick errand in town - start up initially was very stuttery again

Took it down to Autozone to get the battery and alternator checked since the post connection was bad to begin with. My thought was maybe the battery was no good or wasn’t giving a full charge to the alternator. Of course, on start up at the store it fired quick and normal and… passed all tests.

So back to square one: any ideas where to look at next? Thinking electrical at this point and not ignition related.

 

The ground cable on the passenger frame rail is often the cause of starting and other mysterious electrical problems. Easy to check, but follow the torque specs as I’ve seen posts where the stud broke off the frame rail or motor mount bracket from over tightening.

 

Excuse my ignorance/stupidity but where would I find the ground on the frame rail - is there a picture?

 

This pic is from another thread about leaking motor mounts. The ground is the thick U shaped wire on the right side of the pic. From the red circle, the frame rail attachment point is around 5 o’clock and the motor mount bracket point is around 2 o’clock. The mount bracket can be brittle causing the entire ground point to crack off the casting if too much force is applied. The stud on the frame rail can also shear off.

Leaking facelift mounts is a common problem and the black stain on the rail is hydraulic fluid from the mount. Not sure if the fluid can work it’s way under the ground causing a poor connection. Also, be careful if your rail is stained and you want to clean it. The paint under the hood and in the hatch jamb is not clear coated and almost anything used to clean these area will remove the paint down to the primer.

 

Got it - I’ll check for any fluid but am I just checking to make sure the wire is secured and the bolt itself too?

 

Mostly that the ground points are tight, clean, and making good contact. If it were my car I would remove the ground cbble, check its resistance to make sure the wire is still good, clean the ends, clean/scuff the frame rail and engine mount points, and re-connect the cable.

The extra info on the leaking hydraulic fluid was to give some context to the pic, and the possibility, although slim, of the leaking fluid wicking I under the ground point causing a poor connection.

 

So I am waiting to see if I can get the grounds tested but from what I can see, everything looks clean and tight down there.

Slight pivot - after reading other threads throughout years past, I turned it on and let it “prime” the fuel pump for about 5 seconds and the car (cold or hot) turns over with no problems or stutter. I read this could be “Normal” but would that be fuel pump and/or filter or should I check fuel rails? If this is the route I assume I should probably test the fuel pressure to tell?

 

I am no expert but it seems to me; Yes you can check the fuel pressure at the rail - first (easiest) and see what kind of reading/psi you get.
It has been some time but IIRC, mine was @ 50 - 54psi upon start up - operating temp. It's my hope the more seasoned mechanics will chime in/confirm the right psi.

But the simplest question I would first ask is : When was the last time the fuel filter was changed?
If the answer is, or it has been 80K+ to never (under your ownership), I might suspect and hope that it's a clogged fuel filter needing to be changed and not the $-fuel pump-$.
A neglected filter can also cause damage to the fuel pump...if I'm not mistaken.

 

it’s got a tick over 70k, I have only owned it a couple months. Don’t see anything about the fuel filter so far but I got it from a dealer who got it on trade from the original owner so there’s some paperwork I have to go through

fuel filter although easy seems like a fun, clean job haha

Guess I will be looking at doing that this weekend maybe.

 

I've always run Chevron 93 since (new) ownership 2003 and never let the needle go past the red illuminated "slash" When I did my first fuel filter change; I couldn't believe how dark and cruddy it looked - especially after having paid top $$ for premium after a those years!
Oh - it is indeed an utter joy!

But you must go through it at least once during ownership, to have been truly baptized

Best of luck.

 

That is a mystery to me to H2G, Of all the cars I've owned over the years (and I have 12+ now) I have never seen black residue in a fuel filter like this. And it seems most Minis have this. My tank looks to be very clean but next time I have it open I'm going to wipe the bottom with a rag to see if the same residue is in the tank too. It looks more like dissolved rubber in solution, and I have seen E-10 dissolve 30R9 hose on a Jag project I worked on. But it's awfully black so I'm thinking it has to be rubber. Any ideas?

 

By any chance, does the start-up hesitation only happen when the engine is cold (3h+ since last start) and most frequently when it's raining or at least there is a high humidity outside?
That's the description of my issue, I've done quite a bit of diagnostics already and I've came up empty so far, and I know a few others first gens owner do suffer from that issue, but I've never found any resolution online yet.

As for the fuel filter being super black with residue, I can confirm mine looked like that as well. I don't know why though.

 

Boy that does beg the question. For that I'm not sure what the answer is. I can only speculate and might agree with your experience and observations.
My Mini is the only "modern" (and water cooled) car I have ever owned or worked on. I too found the black deposit to be crazy/unimaginable to this degree.

I kinda lament the days of just being able to tap a little, clear plastic filter into your fuel line, in plain sight, where you can monitor and change it out as needed.

But yeah, IIRC - I had read somewhere as one Mini owner had their fuel inlet/filler pipe start to degrade. I haven't read that kind of encounter of a failing fuel pipe since. I have to wonder (or investigate) if that pipe is even made from rubber (?).