I've been trying to figure out a p2096, Lean Bank 1, for awhile. I have another thread going on this and have been stuck at the 'figuring out how to use windows and install inpa software." so i'm didn't want to further splinter and confuse that thread with this new idea.

Firstly: it's a 2004/Pre July Base model. r50 stick shift: 250k miles

What's been done so far....
New O2 sensor (bocsh), manifold exhaust gasket, smoke tested all air lines, and replaced the injectors. car still smells a little fummy when starting and CE light persists.
Low oil is NOT the issue. Lately I have noticed it's much more clacky and tappy / typewriter is a good description. The sound seems to be most pronounced after i start it. I *think* it diminishes some as i drive but it doesn't go away by any stretch.

Was helping a friend on her Honda with a similar code and one of the suggestions to try was a valve adjustment. this rang a bell for me. Could it be something as simple as this or is it more likely that my valve stem seats need redoing? or none of the above? ... the only other thing I figure it could be is a bad cat... but would love to rule out other things first.

 

I've had the p2096 code several times on my 2004 R53 and it's always turned out to be a crack in the exhaust manifold down by the first cat/flex joint. Seems air gets drawn into the exhaust stream causing the lean condition that triggers the CE light. I tried welding the crack (I'm a pretty good welder) and it worked for a while then returned. I eventually fitted an aftermarket stainless header and that solved the problem for a few years. I'm on my second aftermarket header and this one seems to be working out better.
By the way, the valves are not adjustable, having hydraulic buckets on the valves.

 

this is interesting - another thing to check! much appreciated.

 

The "ticking typewriter" noise maybe coming from the belt tensioner or the drive belt is now stretched.
I don't have a base R50 but have experienced the same ticking noise in the past on my '04 (pre-facelift) R53 and replaced the belt tensioner. The noise went away.
As stated above - the valves on a Mini are hydraulic and non adjustable.

You may also want to put an ear (or stethoscope probe) on the plate behind where the crank pulley is mounted. That plate would be where the timing chain is located. A worn timing chain tensioner and/or guides may attribute to a similar noise as well.

Just my "non R50" thoughts as to what the noise might be.

 

it could be oil sludge build up in the chain tensioner, 2 possible solutions a) replace the hydraulic chain tensioner b) flush your oil with some Seafoam (about 1/3 of a regular can should do) before your next oil change, this works best if you do some normal driving for about 50-100 miles before draining it out. Do not exceed this amount of mileage as the thin oil can cause other problems if you go too far.

That ticking can be the tensioner time bomb waiting to detonate, it's a simple component that can ruin your block if you let it deteriorate. The chain guides may not be getting pushed firmly against the chain, allowing the chain to flare out under rotation and slap against the plastic guide channels. The small tensioner part gets clogged with oil sludge over time and no longer expands properly to pressurize the chain guides into place. Just a shot in the dark, but probably one of the easiest and cheapest fixes to improve your MINI's reliability. If you've already gone this route, disregard this message entirely.

 

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Thank you both for the suggestions; great stuff here - i redid the timing chain and all that about a year ago so fingers crossed it's not that failing but it was aftermarket so I guess installing a new chain tensioner can't hurt. but great idea to use a stethoscope to zone into the issue. I have one for this purpose and hadn't thought to try that. :/ ... And will try the seaform idea before i change oil again.

99.999% sure it's not sludge. I change oil as soon as soon as it loses it's opacity and tints slightly dark. which in the eyes of most people probably a bit overkill. i changed it fairly and it was pretty clean considering. Did valve cover a few few months ago it too and it's quite pretty and clean in there. have never had an deposits or dark globs. Will back out the chain tensioner and try another too. thans!