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Engine stalls, O2 sensor error codes + engine updates?

28K views 13 replies 4 participants last post by  Debra Wood  
#1 ·
Hi there! Curious to learn if anyone else has experienced anything similar to what my 2010 Mini Cooper Clubman is going through:

Couple weeks ago: Just another morning; cold engine start; let it idle for a few mins before I reverse out of my parking space — RPM meter needle suddenly drops and engine stalls.

Weird.

Try again. Same same.

And again. SAME.

Engine light comes on.

Gotcha.

AAA tows my Mini to the garage. Error codes suggest engine misfires in 1 specific cylinder plus multiple cylinders. But the car *refuses* to do the same stall for mechanics, so they can’t “verify customer complaint.” Okay...

Three days later, pick up the car after nothing found; spark plugs were checked and looked unworn; coils were checked and almost new. Feeling good! Start her up and go along on my merry way.

But she stalls again, after a 20-min drive — and a 4-hour nap. So the stall was on another cold-engine start. No engine code, but realizing my car hates me, I drop her back off at garage before they close for weekend. Wait another 2 days for news.

Technician eventually finds my car had the wrong spark plugs — someone put “S”/“JCW” spark plugs into my base model, so told the gap difference can cause combustion issues. Makes sense to me! Excitedly approve the full set of new spark plugs + labor and get super excited to get back behind the wheel soon.

Sweet.

Pick up car next day; running smooooooth! Spark plugs seem good! ?

Head toward nearest gas station (running low at this point and the mechanic added some fuel cleaner to my tank), and on my first idle to make a left turn: engine threatens to stall. Yay!

Make it around the corner and make it to gas station. Fill up anyways! Figure I’ll try to make it home (maybe just a glitch?), but engine light comes on *almost immediately* after I leave the gas station. Call mechanic from side of street and they ask me to circle back so they can check the code — okay.

Engine stalls. In the middle of a three-point turn.

AWESOME!!!

AAA her *** back to the mechanic.

Engine codes now suggest it’s the oxygen sensor before the catalytic convertor. Codes are:

2A35 OXYGEN SENSOR BEFORE CATALYTIC CONVERTER, DYNAMICS
- 2A90 OXYGEN SENSOR BEFORE CATALYTIC CONVERTER, PUMP POWER CABLE.

Technician checks fuel pressure — apparently good. Mechanics suggest the faulty sensor is a common problem and they order one to test. Technician also discovers my car has a Mini engine update available from BMW, which he installs. The car now apparently is “running smooth.”

But, I’ve heard that before, right?

Car is still at the shop. And I’m suspicious...

Would an engine update *really* solve error codes listed above? Are they just dragging things along? I know they were busy at the shop today so suspect they didn’t have chance to check the sensor anyway.

Has anyone ever experienced anything along these lines?

Any advice? Anyone experienced in this area?

Should add that I bought my Mini used in November last year. 77k-ish miles. Automatic. Probably a mistake ?
 
#3 ·
you say on cold start its has this issue do you mean from the point where its cold, or do you mean after starting it would after 5-10 minutes starts to misfire, this is important to know what temp the engine is at when it starts to misfire, the 02 sensors and cat dont start working until a temp has been reached and run on a preset switched map within the ecu as such, if before then a software update could very well be a fix,, but i would suspect its fixes a resistance spike from a worn system maybe extending the boundaries to where the sensor reads to the ecu as such,, like when a car is remapped the altered map would cause reading of sensors to change and would always need mapping to fit together to prevent eml lights as such,, ie increases the band where no eml light would light,

this all said if this car was infront of me my very first job would be this,,, see what mileage it has on it, i would also check if tyres are rounded off ie this shows if driven hard all the time as this makes a difference,, then if car was north of 60.000 miles and timing chain check would be my very first check, as these are prone to chain stretch and this alone can cause all kinds of issues,,
ie in your case a retarded out of time engine will dump unburnt fuel air mix on to the upstream sensor and cat, this over heat them and can cause fault codes relating to sensor and cat as a aftermath of chain allowing this circle to happen,,
i have over the years seen so many like this and it fools garages that are not aware of chains and can stretch as low as hmm well lowest oi have seen was 24.000 miles on a car that spent its life with oil on or near the low mark on dip stick,,, hmmm not calling that owner a dipstick of course bt did cost him a new engine as it destroyed it,
ask your garage to push a small camera in to the oil filler cap hole and towards the rear of engine where the pcv breather pipe connects and angle downwards to show the tensioner,, if can see more that 10mm of the inner slider coming out the outer its worn, if can see more than 14mm its on verge of slipping teeth and or snapping top guide off and a big bill £2-4k depending on whether just valves bent or holes in pistons,
 
#4 ·
Hi Mike, thank you so much for taking the time to reply — this is awesome info, and I’ve just emailed my mechanic with your notes.

To answer your question: The very first stalls were cold-engine start, so first thing in the morning after sitting some 14 hours to rest. The second stalls were another cold start after resting for 4 hours, so still a cold start but weirdly after it had been driven just a few hours earlier (and it was parked in the sun this time — LA heat!).

The third set of stalls were more weirdly after driving, so that was after filling up the gas tank and taking off down the street with an almost-full tank. This was the weirdest! As id been driving a good 10-15 mins before it happened. It was a warm day in LA but not excitedly hot.

So, I collected the car yesterday and managed to drive home safe, which is 9 miles. The new spark plugs I think make her feel very smooth and weirdly the engine idle is more stable now. I still feel some fluctuation when I’m at idle for a while trying to make a left in busy LA traffic, for example, but it was by no means as dramatic as what I experienced before when the engine would just shut off.

The timing chain theory is very interesting to me! Does this make more sense to you as well given my descriptions above of when the stalls happened?

The mechanic couldn’t give me specific details of the engine update so we don’t know exactly what the update was fixing, but it does seem to have at least helped.

For now : D

I’m going to go on some more solo test drives today to see how it gets on. Still nervous and I’ll wait to hear back from mechanic on the timing-chain investigation as well.

Again: thank you SO MUCH for taking the time to respond. Can’t thank you enough for the support : )
 
#5 ·
Just re-read my last message and should clarify that the third set of stalls were almost immediately after filling up with fuel. (Top tier, Mini-recommended stuff!)

So I’d been driving for 10 or so minutes to the gas station; idle was very rough during that time but no stalling. After filling up the tank, it started up fine and I took off down the street — but within I’d say 30 seconds the engine light flew on and I pulled over, called mechanic.

They asked me to circle back to them to read the codes and while I was making a 3-point turn to make my way back, the engine stalled during the turn.

I was still able to start it back up and get to a safe space though, before I called to get towed back to garage (because I was scared at this point!).

Hope this makes more sense ? So yeah, weirdly the last set of stalls were after already starting up/driving, so very different to the first and second stalling scenarios.

Oh! Should also add:

My car has some 77k miles on it. I bought it in November so not too long ago (possibly a mistake : D) at this mileage. Interesting to note: the dealer had replaced all the tires and brake pads, so when I had a post-purchase inspection it was all very clean and new stuff (crappy tire and brake pad brands though, I’m told!! Of course, my luck).

So it’s very possible it to as driven hard! I suspect given the great condition of the paintwork on this 9yo car and the interior is almost pristine, the previous owner/s likely had a garage/covered parking for it and kept it in good condition aesthetically, but I’m wondering if it was sold on because it reached the mileage where it all goes south.

And then steps in me! >.~ haha

Thanks again so much, really appreciate your time and help : )
 
#6 ·
at 77k driven normally it will need chain looking at 99% sure will be stretched and effecting how the cars runs add the issues your already having deffo needs checking out before throwing more sensors at it that are prob doing their job reading a engine that valves stay open at wrong times..
 
#7 ·
Hi Mike, thanks so much for your reply! This makes a lot of sense!

I talked briefly to the mechanic yesterday and they said timing chain issues would usually result in a clattering sound, but I’ve sent them your follow-up suggestion as well as I actually think this makes a huge amount of sense! And I want them to check it out if the car stalls again this week.

I’ve also been pointed to another local Mini mechanic that I'll take the car to if the stalling happens again and if my current mechanic doesn’t want to investigate the timing chain. My current mechanic is a Mini and BMW shop but I don’t think they have a huge amount of experience with my particular model; their shop is always packed with beautiful vintage BMWs so I think that may be their specialty and 2nd-gen Minis, perhaps not-so-much.

Anyway! Fingers crossed we’ll all get to the bottom of this. And hopefully I won’t need to sell a kidney to cover the costs ?

Huge thanks, Mike! Appreciate all your time and support! Thank you!!!! ?
 
#8 ·
i have only one response to what the garage said about the timing chain rattle when a issue and its BALLS,,, can mention that to them, i have lost count of the amount of timing chains on prince engines that never made a rattle noise but cars kept throwing up 02 sensor fault codes and another one they do is high emissions at mot gas test, at 77k its on it limit,, what ever you do dont let anyone just install a revise chain tensioner as this will just make things worse at this point,,
its a 5 minute job to check the travel on the tensioner with a mechanic camera system ie camera on a cable pushed in to oil filler cap hole towards rear of engine will show the travel on the tensioner,, brand new can see around 5mm or piston toatlly gone over 14mm ie chain rattle, 10mm out of time but no rattle ,,
link below for cheap way to check this
endoscope camera link below
https://www.ebay.co.uk/itm/4-3-Moni...epair-Tool/183476662406?epid=20027214440&hash=item2ab80fb086:g:yyQAAOSwtJxbu5kF
cheapest way with phone or laptop use coat hanger as wire to help forcing it in,
https://www.ebay.co.uk/itm/5m-Drain...ake-Inspection-Endoscope-UK/352518014235?hash=item5213b6051b:g:pHAAAOSw7rlcBJ4u
 
#9 ·
Hi Mike,

Haha! Thanks for your feedback! Really can't thank you enough for all this input.

So, today:

Just another day! Drove the usual 8-mile trek to the office (the kind of 8 miles that takes 40-60 minutes, heh). I felt the engine fluctuate a few times, but nothing super dramatic.

I had a hunch that my journey home wouldn't be as smooth, so I left early to beat the rush hour. And as my hunch would have it: The engine stalled. AGAIN!

This happened about 35-mins into my journey, so this was another new situation, but the similarity was that it happened while I was at idle, in traffic. I was able to quickly start the car back up after it stalled, and also managed to make it home (another 3 or so miles, at a guess) — thanks to a bit of detouring that took me down some safer streets.

So the car is now parked at home, waiting for the mechanics to open in the morning. They've offered to troubleshoot it again, and I've passed them literally all your feedback as I definitely want them to investigate the timing chain. It makes so much sense to me! If they don't have any answers, I'm going to take the car to another mechanic, as this is a 4th shot. Third time definitely wasn't lucky!

No engine light came on this time, so I doubt there will be any codes to read. Curious on your thoughts for me to invest in my own code reader?

Thanks again, so much — fingers crossed we get to the bottom of this soon : )*

*smiling but crying inside ^^
 
#10 ·
the only two good cheap readers i would say are autocom cdp plus, or wow wurth snooper i have both,, links below. there is nothing around for the price that will work on pretty much every on the car and every car on the road on near dealer level,
autocom cdp
https://www.ebay.co.uk/itm/2017-Blu...Auto-OBD2-Diagnostic-ToolYT/143155392750?hash=item2154b9f0ee:g:b8sAAOSwiZhceqYB
qurth snooper
https://www.ebay.co.uk/itm/For-WOW-...ool-scanner-for-Cars-Trucks/282740774401?hash=item41d4a9d601:g:G6MAAOSwuk1Z2~kD

like said i have both what one dont cover the other will. also the snooper gives some very good pages of data on a most cars well worth the money it also does 1 click scans the whole car, the autocom is good on live data hence why i use use this a lot more than the other, with a fault like yours the autocom would be best one,, but if can afford both get both and mount both n same laptop, ie laptop without internet connection and anti virus ie only use laptop for diagnostics , i have windows 10 and windows 7 running them,
the next of the list of diagnostics tools starts at around £800 for hand held thing that to be honest wont have the features these two cheap ones do
 
#11 ·
Thank you so much! I’ll check those out — may have to wait till after this month’s mechanics’ bills to invest but thank you for the great pointers : )

Mechanic picked up the car this morning but seems adamant that it’s nothing to do with timing belt. I’m personally confused by this as they have literally no other ideas on their side, so I’m baffled why they won’t check it out at least. They are leaning towards the faulty O2 sensor but that’s all they have right now.

I’m calling around other mechanics and will move the car tomorrow to another shop if necessary.

It’s a good job I love my stupid Mini. Though ask me again after the next round of bills; I may change my mind... ^^
 
#12 ·
worrying he thinks its has got a timing belt,, and he not open minded to what it could be but dont know what it is, i see this all the time have had many jobs that have been looked at by other so called techs that tell the customer it needs a new engine or scrap it,, and all because they think a timing chain is for ever hmmm 20 years ago yep it was not anymore, HO i'm glad i dont treat anyone like that lol. i love being proven wrong as it means i have just learnt something new lol. with those miles on it and never been done it needs checking ruling out or in
 
#13 ·
Am not as techy as Mike but I can confirm that my justa R57 2009 was at 48K miles with your symptoms and the solution was a replacement timing chain (which I did myself after much Youtube veiwing, a Haynes manual and beer. I can also confirm you are using the wrong shop if he thinks it is a belt and is faffing around with sensors and spark plugs and wasting your time and money. With the correct timing tool kit, replacement parts and home tools it is DIY job if you have any previous skills. I would be wary of continuing to drive it until chain is replaced.