Hi all... posting here to try to get a few possible scenarios (even though there may be to many to count... I thought it was worth a shot, since its the weekend and the mechanic isnt available to look at my mini until Tuesday)

Model: Mini Cooper S 2008

Problem: Shaky driving, lacks acceleration, check engine light is on (yellow) - stays solid for aprox. 5-10 mins, then will beep and flash for aprox. 1 minute before returning to solid, no smoke or abnormal exhaust being emitted, no oil leaks visible beneath car or on surface car is parked on.

Checked oil level 5 days ago, appears to be low, added 1 quart of oil. Car ran fine for about 20 hours, then while entering the freeway began to shake and check engine light came on as stated above. Fortunately was still close enough to my office parking lot, where I got the car back to so that I wouldn't have to continue driving it.

Had a friend who is knowledgable in cars (on a mostly hobby basis in terms of engine repair, he specializes in electrical issues and repairing instrument clusters)... but since he was in the area, swung by to take a look under the bonnet with me. He attempted to check for a code with his handheld reader, but it wouldn't pull any codes - which Ive heard, some codes will only appear to a mini mechanic or dealer. When car is running, feels and sounds like on the the cylinders is not firing. We checked all four coils, and identified that three were working fine, one was not. The problem coil was getting accurate power, and was clean and free of visible damage. we then pulled out the spark plug beneath that problem coil and found that the plugs centre electrode and the arched ground electrode were almost nonexistent - and there was black corrosion all around the top where the electrodes are.

We got a new plug, and replace it. Car still running shaky, and idling very very rough, check engine light remains on. The cylinder that that faulty plug is married to still appearing to not fire.

Curious is anyone has any insight on what some possible scenarios might be for this problem... and what might cause the electrodes on a plug to become so badly damaged like in this case (Ive also attached a photo of the damaged plug). Im planning on having it towed to my mechanic (which is a bummer because its a long tow... but since most of what Ive read about these symptoms and particularly the check engine light flashing and beeping makes me scared to drive it al at all).

Thanks for the help!

 

I would err on the side of caution and replace all plugs and coils, just to start with. How many miles does the Mini have? The plugs appear to have never been replaced.

 

'07 MCS OEM plugs were NGK5992 (ILZKBR7A-8G). These are discontinued and replaced by NGK95770 (ILZKBR7B-8DG). As enoe01 suggests, at least replace all 4 plugs. If you suspect a bad coil, try swapping the suspect with another and see if the problem follows.

With the ground electrode missing on the shown plug, you should consider whether or not it was worn gradually, or broken off and rattling around in the cylinder. A compression or leak-down test would prove informative, especially if your oil loss was sudden.

 

It's likely the spark plug pieces that broke off might have caused damage to the piston, head and/or valves. A leak-down test would be a good place to start.

 

As far as idle is concerned I would always check, and replace/repair if needed, the plugs, coils, Carbon build-up, HPFP. I've had similar issues and my MCS has seen improvement upon replacement or maintenance of each item I mentioned. Have an appointment to have my HPFP replaced later this week (final thing left to do on my list) and hoping the car is good as new again.

Carbon cleaning made a huge difference with the rough idle I was experiencing. The DIY that Pelican offers on their site is actually quite easy to do, just requires some time and patience.

My HPFP is giving me issues as well but the idle and start-up is not as "rough" feeling as it was when my valves were caked with carbon.

 

How many miles? Have you done a carbon clean up yet? There seems to be a fair amount on that spark plug. You really need to get a tool that will pull the code as that will give you the best idea of what is going on with your MINI. That way you're not just throwing parts at it. As GAT said, our DIY for the clean up will be most useful to you if you do not have the walnut blasting tools.