Hi, I'm a relatively new member, 2004 Mini, 73K mi, manual. "Service engine soon" light on, I tried to reset it following instructions and got miles interval to reset, but light still on. I change oil every 10K. Hooked up Acton code reader, says mixture too rich, can get the code # later if needed, but does this sound familiar? I deleted code but it came right back on. Seems to drive fine, mileage still good, but it irritates me. Hate to spend a few hundred or more for something I can fix myself. I was thinking maybe O2 sensor needs replacing, or cleaning if that's possible, but thought I'd post this for feedback. Still has original plugs, supposed to be good till 100K per manual, but maybe someone has other ideas. Air cleaner fine. Thoughts? Thanks - Dave

 

Well first off, I would replace your plugs even if it isn't related to the problem 73K is enough miles to change them at.

Look at your tail pipes. There should be some black soot on them but check to see if there is an abnormal amount on the tail pipes. Also, give it some gas (fold down the rear seats and open the hatch) and see if there is a fair amount of smoke coming out of the exhaust.

Do you have a base MINI or an S?

 

Thanks for your reply. Base mini, not S. No excess soot; maybe a 1" wide area on bottom of pipe where condensate drips, but none on bumper or other edges. Engine doesn't seem to be smoking at all. Runs fine as usual, no power loss, mpg loss, etc. I'll try a plug change this wknd; plugs supposedly good for 100k, I usually replace at 90K, but I suppose a weak spark could lead to incomplete combustion in 1 cylinder. Any "enthusiast" plugs you recommend or ones to avoid? O2 sensor was supposedly OK on the code reader. I thought if it's too rich it sent signal to computer to inject less gas, so if computer bad or if one of the wires from sensor to computer weren't sending proper signal, those were possible sources. I thought about disconnecting sensor, removing and lightly cleaning it too, don't know if that's even possible or ever done, or if certain solvents need to be avoided. A Mini brand 02 sensor via internet dealer is over $200, but a Bosch that will supposedly work is about $60. Any knowledge if aftermarket sensors OK? I'll change plugs first, let you know if that does it. Only other thought, which I can't imagine would do it: have always run mid-grade, 10% ethanol, about all you can usually get here in the Kansas City area, then found pure-gas in premium (no eth.), so have been running only a 5% eth mix for last 2-3 tanks, have noticed definite 1-2 mpg improvement (50% prremium pure-gas, 50% regular). I assume it's just a coincidence that light came on after this change. Thanks again for your input. Dave E.