Ok, so I've posted on this before, but didn't get very far. It seems like the car has the same thing as everyone elses'. You turn it on, it fires up and then stumbles for a couple seconds. It car will have hardly any power till the motor gets warm. The car has been getting terrible gas mileage for quite some time now, about 28mpg on my daily commute, which is mostly highway driving. I say terrible as I've seen it go as high as 38mpg. It's an 03 cooper with 99k miles.

Maintenance that's been done/parts replaced:
-oil changes religiously, 5w30 Royal Purple 15k mi oil
-Spark plugs
-plug wires
-coil
-fuel filter
-pcv valve
-air filter
-both oxygen sensors

I don't think it's an issue with the cat being clogged as the exhaust flow coming out the tail pipe is pretty good. I can feel it from 3-4 ft away.

The last time I pulled the codes it was telling me there was a misfire on cyl 4. Do the Mass Air Flow Sensors go out on these cars often? Because it seems like that's the only thing I've got left to replace. Is there any place other than the dealer that I could source one?

Are there any other ideas?

Also, forgot to mention, it isn't the gas. I run Shell 93 octane only.

 

coolant temp sensor? ,o2 heaters crapped out? i dont knowe what the voltages are sposed to be but if you can find out i'd look at stuff like that .

 

A coolant temp sensor will cause a car to run poorly and get crappy gas mileage?

 

check compression. Check injectors (you can move them around and see if the misfire moves). There's no MAF, there's a MAP sensor and a T-MAP (both if you have an S, just a T-MAP if you have a Cooper). These do go bad.

Matt

 

my focus was on the running crappy when cold part .

 

Can you find these T-map sensors outside of a Mini dealership? I've looked on minicarparts.net and minimania.com, but haven't found much. I remember minmania having a lot of stock replacement parts but have been unable to find any lately.

Just out fo curiousity, what does the T in T-MAP stand for?

 

Nevermind, found it and ordered it.

 

it's a combo temperature and pressure sensor used to determin air density.

Matt

 

I'm dealing with same issue. Please post result, positive or negative. Thanks.

 

I recently had this stumble, thought it was bad gas....got p0030 code engine misfire, well I removed my msd coil threw the old coil back on and has been running great since...it started one rainny night. I did tink the coil would fail so soon or would misfire? Try it as well as the MAP sensor.

 

Bump for an update? Any luck with the sensors?

 

I finally got around to replacing the MAP sensor and figured I'd post the result.

The issue had been getting worse, especially with the weather getting colder, leading me to believe that the MAP was the culprit.

Replacing it was a serious PITA! I had to loosen up the radiator shroud, so I could take out the air box, snorkel and intake tube. The MAP was tucked up behind the throttle body, making it very easy to strip the torx screws as I couldn't get straight at them. The old MAP sensor had a strong smell of petrol...isn't usually a good thing, unless you're sniffing petrol.

While I had all that crap out, I decided to take some throttle body cleaner and a toothbrush to the TB. It really needed it! Hopefully my wife doesn't mind I used hers....I rinsed it out and put it back though.

I took it for a test spin and it felt better than it has in a long time. I was even catching some scratch going from 1st to 2nd. I still need to clear the CEL, requiring a trip to Advanced or OReilly's, but the first impressions are positive.....for once.


Edit: Nevermind. It threw a code when I went into town yesterday. I quit. I'm taking it to the Stealership.

 

Ok, I threw up my hands and took it to the dealer.

They said there were multiple mis-fire codes on all cylinders. They performed a leak-down test and the results were not good. I found it interesting that after seeing these codes, they went straight to a leak-down test....almost as if they expected it. I'm sure Mini won't stand behind it and offer some sort of goodwill, even though I have thorough documentation of oil changes/maintenance and only put Shell 93octane in it.

Right now, I'm trying to weigh my options. I know there are places that have some kind of fuel system/intake cleaning service. Maybe this could clean off whatever build-up there might be on the valves. It could be as simple as that...not likely though.

Other option is to rebuild the head or purchase a rebuilt/reman head. The best price I've been able to find is $950, not including the cost of R&R.

Finally, I could do nothing and sell the car cheap as a "Mechanic's Special". This would be a shame as it's in decent shape and a nice little H-Stock autoX car.

Thoughts?

 

Well,

HERE IS YOUR FIX.

1. Buy a can of Seafom from Walmart.

2. Use the PCV vacuum line to suck it in.

3. Shut engine off - sit 20-30 min.

4. Start it up and blow out a HUGE smoke cloud.

Car performance will be immediately improved. You will be surprised.

You can also search Youtube....someone posted a video to watch. Don't be afraid to do it.

IT's easy!!!

 

SORRY...... IT'S "SEAFOAM"...... MY BAD

 

I've done it. The cloud was quite impressive, but it didn't change anything. I was disappointed as I did it to my Volvo and it made a huge difference.

 

Bummer... I'm surprised.

There is a TON of owners throwin #4 cylinder misfires. Usually, the Seafoam fixes it or helps out alot.

Good luck.

 

one in market place for 450 with cam ; 300 without .

 

There's also a Thumper head in the marketplace.

 

You say the result for the leak-down test is not good. What did the tech say? Is the head kaputt?

 

I went and grabbed the car from the dealer. I also got the leakdown test results.

55% - 60% - 65% - 90%

I question the accuracy or how carefully they performed the test. I would think if cyl 4 was leaking at 90%, the car would hardly be able to idle. It idles fine until the cyl is completely loaded up with fuel.

But, looking at those results, I think that the valves are kind of boogered up, but pot 4 is higher for a reason. Crack in the head at cyl 4? Bad HG on cyl 4? How prone to cracking are the NA heads? I have noticed a bit of a coolant leak.

I've reasessed and still have three options, assuming I don't need to rebuild the head......I really reallly REALLLLLLLY don't want to rebuild this thing.

I can sell it as is. Possibly to a dealer (Carmax) for wholesale.

I can take it to this indi service place in town for imports that are very good, better than a dealer. But just as expensive....maybe moreso.

Or I can take it to this indi mechanic that is fearless. He'll work on anything and he's clever. He knows all the old-timer tricks for determining if something is bad without ripping it apart to see.

 

i think what you're seeing is the percentage of what's left and maybe not the amount leaking out .? 90% leak would be quite obvious . even 45% would be evident. blow bye would maybe be huge (valve cover) backfireing maybe but it'd be something . just do another test . still could be ignition anyway

 

Sounds like a head gasket (coolant) and carbon on valves. Time to take it off for a look see to see what's wrong.

 

If it were to come to replacing the head, is there a difference between an R50 and an R53 head? I didn't know if the big difference between the two engines was in the bottom end, or if they were just all together different.

I saw the couple of heads for sale in the Marketplace, but only some of them had designated that it was from an S or just the standard Cooper.

 

that can take higher heat. It would work on a Cooper though...

Somethin ain't right with that motor for sure. I'd go to your fearless buddy for more diagnostics. While it's a new computer controlled car, it's still just an engine and old school knowledge is real good.

Matt