I have an 08 JCW and replaced the coils and plugs about a month ago after it was running rough. That fixed it and all is well.
This weekend it started doing the same thing; weird/hard start and then really rough idle. It accelerated OK, but still not normal. (should mention that the first plugs were Bosch Plat double). When I took them out, they had a red hue on the electrodes and threads.

This time around, I took the coils (Duralast) back and replaced them AGAIN (more Duralast), but instead went with NGK R plugs and it started doing the same rough idle. Codes come back for same misfire and a reco to replace the coils and plugs.

People seem to really like the NGK, which why I went with those. I highly doubt out of 8 coils and 8 plugs that they all had a defective unit?
Any input, suggestions, or alternatives would be immensely appreciated. (outside of pushing it into the Mississippi river).

Thank you!

 

A red coloration is usually due to additives in the fuel leaving micro deposits, or as a result of rust in the fuel system.
https://askinglot.com/what-makes-spark-plugs-turn-red
https://www.autolite.com/docs/defaul..._plug-tips.pdf

How many mile son the car?
What is the general condition of the fuel system? Its possible your fuel system pressure is falling off - HPFP dying, fuel filter getting clogged, or both.
Carbon deposits in the intake?

 

Code numbers?
Mods?
When was last HPFP change?
Fuel pressure at start-up?
Check for leaks between air filter and intake manifold --- loose clamps, torn / broken fittings?
NGK Iridium plugs seem to be the preferred choice. Check for correct part number and plug gap here --- https://www.ngk.com Be extremely careful if setting gap, center conductor is fragile.

 

Hey - thanks for the reply. Those are good suggestions.
It does have an aftermarket air intake (AEM) & catch can (AEM), but otherwise stock. It has a noticeable -I'm running on 3 cylinders-misfire; not like a crack in a boot. It is worth (and I will do it) check all of the connections and hoses to make sure they are in tact and tight.

I don't know that the HPFP has been replaced; what's the best way to test that? (but it does have the strange, sluggish start-up when it's hot and then proceeds to run off of 3 cylinders at idle. (Seems to start better when it's cold.)

Code is P0303 - misfire.
My local MINI dealer has the OEM coils and plugs, that I'm going to try in the morning. I can't imagine it is the plugs at this point, but worth a shot? Unless you tell me there's a good way to check the HPFP!

 

If your code P0303 is consistent after all the plug and coil replacements and doesn't change by switching #3 parts with another cylinder, that implies a problem with cylinder 3 --- injector, wiring, compression, ??? Any chance #3 compression is shot --- can you get CR #'s --- hot and cold?

Make sure all your replacement parts have the correct part numbers. Some auto parts stores will sell you parts for a 1st gen mini if they don't have the correct part on hand.

As for HPFP, the only test I know of is the starting fuel pressure. If you don't have an OBD II scanner, try to borrow one from the local parts store and monitor Fuel Pressure while starting the engine, preferably a cold start in the AM. A forum search will produce several HPFP pressure test results --- I can't remember the minimum numbers.

 

Check compression. You wouldn't be the first with a melted exhaust valve on cylinder 3.