recently my R53 2005 (43K miles) had shown some rough idle (very intermittent)

and I was thinking it's oxygen sensor, but since there is no CEL on, I doubt it's the cause.

any idea what can cause that?

do I need to take it to stealership?

 

BTW, it has only 43K miles, though it's almost 9 years old car.

any idea what could cause that?

and I use royal purple syncromax as transmission oil. (6spd manual)

 

I would change the sparkplugs if you haven't done that yet.

The threads in our cylinder heads are very soft, so only do it when it's cold (really cold, like after being parked overnight), use a torque wrench, and recheck torque after a few warmup cool down cycles or a hundred miles or so.

 

bet if you find the reason of the idle issue, you MPG may pick back up...
One thing I would look at is the Coil...
The OEM coil has Nickle PLATED Iron plugs...and they tend to corrode...
so unplug the sparkplug wires, and if you find rust, you might try a to clean it off, then add some dielectric grease to help the connection and keep out moisture...be sure to check the wire side of the plug wire too...When I found mine, I got new wires, and a new coil (I choose MSD cause it had brass plugs)....many use a screaming demon, etc...reality is a coil does not really make more power,,,the OEM is fine if it works good, and has no corrosion.
If you have an Ohm meter, checking you wire might be good...along with feeling the outsides for cuts/chafes....
New plugs, installed with a TQ wrench would not hurt.
Hopefully the car has always had good 90+ octane fuel...many a MINI has burnt a valve due to lower than required octane....

 

I always add 90+ gas, usually get few tanks from costco and then get another tank from Chevron or Shell.
so I think the gas should not be a problem.
BTW, I saw the tail pipe turn black in the bottom end in the past few months, is that a sign the burning is not good. I may need to check the sparkplug and coil. thanks!

 

Get a blue tooth elm327 for$25
Get torque pro for android tablet or phone

Check fuel trims......they will tell you a lot of what could be wrong. If you don't know about trims.....reseArch this. It is the single most valuable piece of information to diagnose your car.

More information would com from dis v57

If tells you everything about your engine......spark plug fire....fuel trims. O2 readings. Everything

 

http://www.meritline.com/elm327-blue...Fc9i7AodBVsA0Q

Elm327

Then.....get torque pro app for android tablet or cell phone.
If you get that far I'll show you how to use it. It's not learning friendly.

You will check fuel trims. They will tell you why your car is running bad.

Your o2 sensor may be soft failing. Your car can sound good, run good, and have a problem. You'd never know. My rav4 fuel trims are +10 right now....no lights and no performance loss.
+10 is too high.

Any way. The check engine light is when parameters are so far gone that the computer doesn't know what to do. So it finally warns you something is wrong. Usually the problem occurs well before that.

With the elm327
You will check o2 sensors the right way. They create a signal. Electrically bounce between .1 and .8 at ALL TIMES. Idle....high rpm....all times. If they are consistently out of range they will be bad.

Like.....if it goes to .3 to .8 all the time......it's bad.
The elm will show you this live data.....and you can graph it and print it out.

You can guess that this or that is wrong......why not know for sure. Drive down the road and watch it happen. You don't have to guess at all. You can diagnose without throwing parts at it.

 

I'm getting my scanner now, and installed the android app already.

will try tonight, thanks for the post.

 

tried the OBD scanner, no fault code and O2 sensor do go from 0.1 to 0.8 (most of time), do have one or two curve shows higher than 0.1 bottom and lower than 0.8 peak

any thoughts what could be fail?

 

IMO don't' go chasing ghosts....
You car is idling rough....
Most mini's ALWAYS have a hint of black on the tailpipe....they run rich from the factory(most every sc car does to protect the motor)......
Fuel trims WILL vary for many reasons....
Even e-10, aka ethanol 10%, 90%gasoline will cause fuel trims to run high.....
Just saying if your O2 sensor was so bad it made the car run so rich it idled poorly, YOU WOULD 100% HAVE A YELLOW LIGHT/CODE.....

 

Changed plug and wire, scanned OBD O2 sensor seems good
I do see a black tail pipe

What else could cause tHis?

 

Did you get any further diagnosing this? My 2002 R53 also has a rough idle. I took it in to a independent MINI shop and they ruled out timing and said the only rattle they heard was in the supercharger.

This doesn't make much sense to me since the supercharger isn't engaged at idle - but I'm not a mechanic.

My next step is to switch out the spark plugs. Did this make any difference for you?

 

The fuel trims will tell you a lot. There is nothing more powerful to understand than how to read and understand fuel trims.

Read them.....there are short term and long term.
The short term will fluctuate. And can go high....and lower than normal
It is the long term you need to be looking at. The long term is important.
The short term makes the long term. Long term is the average of many short terms.

Rich is -10 to 0
Lean is 0 to +10

When trims reach +5 car is starting to run too lean.
Stoic his 0 and is a perfect engine. Very rare to see 0

The computer sees lean mixture...it tries to add fuel.
If the computer is reading wrong...........it is adding fuel to air that doesn't exist. The positive fuel trims mean the car is running lean. The rich mixture and low mileage is probably from a lean mixture. Not a rich one.

Maybe a super charger is supposed to run rich....I don't know. I don't have a mini yet....and probably won't get one as I'm after reliability. I already have a bmw that cost a lot to maintain. A mini as much as i like them is still....a bmw. I will have to buy a mini knowing they will start to fall apart at 100k


Either way. Catalytic converters don't like rich mixtures. It makes them run very hot because they are trying to catalyze more fuel than they were designed too.


I like fuel trims in the +3 range -3 range.

You can get readings from a well running mini and compare them.


It doesn't matter......o2 should be read anyway after 100k. It is a consumable sensor. After 100k the are said to be replaced as preventative maintenance. They wear out.
There are 2 of them. One before the cat. One after the cat.
The one before is the primary. It helps control fuel along with the maf sensor.
1 of the 2 main important sensors.
The second sensor after the cat. Tells the computer that the first sensor is working. It should not run between .1and .8 only the first one.

There are variations.....you just don't want consistent .3 to .6 or .1 to .4
Stuff like that. At idle at high rpm. They should always behave the same.

My fuel trims were +10. After much graphing and comparing with another car. We found maf sensor to be slightly off. Just slightly. We found it to be low quality Chinese knock off. This reduced mileage. I replaced the sensor and now run at 3

 

Charted data

 

Graphed fuel trims
The 10s and 15s killed the average.

Made long term fuel trims +10
Way too high

 

this is my OBDII scan results

it looks the load value is too high, but I'm not so sure
O2 seems fine, can anyone help take a look and shed me some lights?

thanks!

 

Your long term fuel trims are high
O2 sensors look fine.
Now use short term fuel trims.....see where the go above 7. At idle....high rpm....cruising. Or right off idle

 

Bank 1 sensor 2 looks a bit sluggish, compare it to Bank 1 sensor 1, which is happily toggling back and forth around stoic.

 

Sensor 2 doesn't bounce. It should be consistent. It only tells the computer the cat is working .....it shows after catalyzed air fuel ratio.

If all the fuel is catalyzed properly. It shouldn't really ever move much

 

Try this https://www.northamericanmotoring.co...ni-viagra.html

Some people have had luck with doing it.

 

Actually sensor 2 does move quite a bit, is that indicate the catalyst is not working properly?

And also the load value seems high, any thoughts

 

It could mean the cat is on its way out when it moves like that. The cat should last the lifetime of the car. Most don't because of high fuel trims due to worn components. The cat uses platinum to convert what's left over in the combustion process into something less harmful to the environment. It is designed to work with a stoic mixture. Anytime your car runs rich it wears it out quicker. Any time car runs lean.......fuel trims go up........the computer sees lean and says..........Add fuel

So in a rich condition...car runs rich, on a leans condition........Car runs rich.

A lot of people just throw o2 sensors at the problem. It doesn't fix them. I don't remember if the second o2 is allowed to move much. I do know it shouldn't bounce like the first one does. I don't understNd the high load on your car.

I do know you are running lean.
Bad maf
Vacuum leak
Non sealed or cracked intake post maf hoses
Not enough fuel being delivered.......pressure regulator. Weak pump

So......too much air or not enough fuel
Bad sensor.........thinks there is too much air when there really isn't

 

http://forum.e46fanatics.com/showthread.php?t=897616

Go there......read all of it. Some won't pertain to you because it's an e46 bmw
Any questions......the guy who wrote that is a great guy to ask. He's knowledgeable and patient. It's not mini but it's a lot of universal information.

He can tell you how the secondary is sposed to act. You might try to get him involved. The knowledge on that sight is amazing......because the all have problems......they are into a lot of advanced diagnostics. Almost all sensors on every car behave the same. An o2 on a ford has the same .1 to .8
Voltage reference that a mini has.

But a maf on 4 cylinder won't be the same as a 6. All other sensors besides the o2 are different voltage references. If you can get good maf references and coare them to your graph you will know more

 

Hoping someone on this thread can provide some help to me. Short story, getting bad MPG (~16). Car does fine on the highway (~30mpg) but pulling away from a stop drops fuel economy dramatically.

I've output the relevant data from DashCommand - my car appears to be running lean. My long-term trims also show the most variation while I'm at idle/neutral....

Which fuel trim sensor should be my reference point? Sensor 3 suggests I am running very lean.

What can I do to diagnose this further?

Anyone tried a MAF cleaning on a R53? (I know, I know, they are MAP/TMAP sensors, but people have suggested cleaning improves the situation).

Just at a bit of a loss what my next steps should be....

 

Sounds like a vacuum leak. That would affect it mostly at idle. Check vacuum at idle......I'm thinking at least 18 to 20psi....buy or rent a vacuum gauge. Also....make sure thermostat is still good and staying where it needs to be. They are electrical and wear over time.

What is sensor3? 4 cylinders should have bank 1 sensor 1 pre cat.....and bank 1 sensor 2 post cat
6 cylinders have split exhaust manifolds.......bank 1 sensor 1..... Bank 1 sensor 2 post cAt first 3 cylinders
Bank 2 sensor 1.... Bank 2 sensor 2 second 3 cylinders or cylinders 4 5 6

You car should have no sensor 3 unless it's back by a secondary catalytic converter.....

So check LTFT bank 1 sensor 1 and 2

Check your o2 sensor voltages. To find out if maf is working correctly you need the specs at idle.

Always clean your maf first. Only use maf cleaner.

Maf sensor is platinum coated hot wire. Computer keeps it at 200° celcius with electricity... Air cools it down. What it takes in electricity for computer to keep it at 200° with air cooling it is calculated and used to control fuel
As k/sec. You need to know k/sec spec for maf at idle to know if its bad.

Ok....so maf gets dirty.....dirt coated platinum wire. Wire still gets hot.....but air cools down dirt instead of wire......giving a wrong reading.

Any other cleaner besides maf cleaner leaves a residue......residue coated platinum wire reads wrong.....air cools down residue instead of wire ...hence non residue maf cleaner.