Hi guys,
We have a high mileage Mini R50 with 174,000.
I'm pulling a P0303 Misfire on #3 code. Initially it had a P0313 (i think) stating a low fuel issue. After reset this has not come back.
I rest the codes and this keep coming back after a few minutes..

I did a compression check:
Cyl 1 = 154
Cyl 2 = 159
Cyl 3 = 80 to 100 and up to 115 when it wants to turn over
Cyl 4 = 136

We tried the Seafoam trick. Not much love there.
Did a plug wire swap (3 with 4) as well as a plug swap. No dif.
Just got back from buying a new coil pack, Same results.

It stutters and misses badly after it reaches the check engine light status.
When it has been reset it still stutters a little at idle but is at least drivable.

If I reset the code, let it sit a while and drive it, it appears to work ok until it just goes "bam" the light comes on and instant crappy idle and misfire.

What would cause it to run ok when reset then go into misfire mode after driving for 10 minutes? I suspect this is heat related.

Either the valves heat to a point when suddenly they can not hold pressure, or the pistons, same thing. But it is instantaneous, not gradual.

Seems like if this was a burned or corroded valve it would always be bad right?

I realize #3 is low pressure any way, but this sudden misfire, like throwing a switch, is befuddling me.

Any idea how we can get a few more miles out of this car? Or does this sound like a complete head rebuild.
Thanks for any ideas.

 

I just went through this similar issue on my Mini after checking everything and turned out to be a valve issue. My code was with cylinder #4 (P0304). I pulled the head and had a machine shop work their magic. I reinstalled everything with new gaskets and no more codes after 4 months.

 

Thanks for that reply Debi. I just managed to do a few more tests. Rechecked the compression on 3. (80lbs) put a little oil in the cyl to test for a compression change. No different.

It is running OK this AM when completely cold BTW.

Are there visual instructions somewhere for removing the head on an 02 R50 non S motor?

Sure would be nice to figure out a way to degunk the valves directly without disrupting the head.

Did you have to replace any valves on 4?

 

I had the same issue, P0303, days after buying my used 2002. Steady CEL and occasionally flashing CEL and very rough running. I sea foamed it 3 days in a row. Day 1, still had the problem but 50% better. Day 2, problem gone. Day 3, just for good measure. That last treatment was a week ago and still problem free. I haven't had the CEL reset yet, though. I'll probably do it tomorrow.

 

I used all these to do my head gasket:

https://www.northamericanmotoring.co...questions.html

http://www.*********************/for...#axzz3LEVRTBqr ( nam doesn't like motoring alliance)


And a new one from modmini
You can use the r53 directions. It's not that difficult but unless you're an experienced mechanic I don't think I would recommend doing it. Although with all that help maybe you won't have a problem.

Take a look at this post for some potential issues that might arise from doing the head gasket https://www.northamericanmotoring.co...ing-cover.html

 

Thanks for the links. I've been watching them a lot. the original r50 2002 motor is a little different, but I managed to get the head off. The #3 valve is definitely cracked. As well the cam lobes are gouged down and a few exhaust rollers are toasty. All the valves are leaky too.... Did an upside down water test with air compressor.

So going to sort out a new used cam tomorrow and some after market rockers.

The Cam bearing retainers were in an odd order : From left to right 4,5,3,2,1.
Years ago,we had a broken spring and had to take it back to the dealer for the worlds most "expensive" tear down fee. Well at least they got the bearings in the wrong order after all that money.
Jeez.

 

Sucks you're having so many head problems and even worse that the dealer couldn't fix it correctly.

You check any of the vendors for a complete rebuilt head? WMW has a service for 500 , saw sneed has heads for 500 too, and I'm not sure, but I think rmw is in California, maybe they are close to you.

But maybe you can piece it together for less. Good luck!

 

I just got a Sneed rebuilt head and will be installing it this week. It looks good and I'll let everyone know how it goes. It was $599 and I got a gasket set and head bolts from him too.

///Rich

 

That Sneed head is sounding like a good deal. Good luck with that!

For now, I have located a good used cam and have ordered 2 rockers and a valve. I hope I can lightly lap this back into a functioning head. Anyone have any advice if I were to do a light valve lapping? Or mild cleaning? Q: do all valves need to re seat back into their original position? I would think so. But would be nice to separate the pieces to clean. And what is a good method for cleaning the chamber to get rid of the carbon buildup? i do have a sand blast tank. Is it possible to mask off the sensitive areas (valve guide areas, deck and port areas) and clean it up that way?
Perhaps walnut shell blasting?

 

Like all MINI heads when they need rebuilt, they need valve guides so that is the most important part of the rebuild. Then grind all the seats and valves or replace the valves as necessary. this is what we do with every rebuild we do.

 

Is there a spec sheet showing the proper stock exhaust valve height measured when the valve is seated? What are allowable tolerances? Just want to check how installing a replacement valve will measure out.

 

Wuddya do when the little lifter ball end plastic ring breaks on the rocker arm end? Can this pert be purchased? or do you have to buy a WHOLE NEW ROCKER ARM??

 

I replaced 2 of the exhaust rocker arms because of bad rollers. Would hate to have to replace another because of the little orange plastic retainer (that broke) on the tappet end. is this little plastic retainer piece available. Can't realty find one on the internet. Hmmm.

Anyone ever replace these orange plastic things? OMG this is such an achilies heal for a tappet that goes a million miles an hour

 

OK, Replaced 3 rockers, found a gently used cam, did a valve job on the exhaust side (intakes were fine...New gasket set various other tools and parts...Got it all back together....

She runs great! More power. Kinda like new.

Get this.

Now the 5 speed is sticking. Mostly in 3rd gear.
(insert sad face)

Coincidence? Could jacking the motor up a little cause a mis alignment? Hmm.
We just had the clutch replaced last year and prior, had a clutch fork repaired.

Is this the dreaded output shaft bearing issue with this trans? Or could this be something simple like low oil?

Just seems a little weird to have this occur right after taking the head apart.
One thought, When assembling the pieces near the battery box, I pushed down on the break reservoir and hear a little crack like the plastic reservoir has gotten brittle.
Does this hydraulic system feed the clutch in any way? Maybe it has lost pressure?

ready for a new topic with this I guess.....