Hi there, I have a 2004 R53 Cooper S JCW. I had a bad exhaust (ebay header kit) on for a little while that had no catylitic converter. It gave me several check engine codes. I then replaced the exhaust with an OEM exhaust (manifold-catylitic converter). The O2 sensors got pretty fowled up and I replaced the cam position sensor (had codes for those too). So in theory I've replaced everything that I had codes for. I've used an OBDII scanner to clear the codes but when I shut the car off and then turn it back on they all reappear.
Do I need to do the ecu software reset? I suspect when I had the bad exhaust on for a little while, the computer tried to compensate for the faulty exhaust and messed with fuel ratios, timing, etc. But I don't know Minis all that well to know what I should try next. Any ideas from you Mini experts would be awesome. Thanks!

 

Welcome to NAM. I am going to move this to the Stock Problems/Issue folder as the exhaust manifold is the same as the S.

I cannot tell from your posting but did you replace the O2 sensors? What codes are you getting?

 

Yes I replaced the exhaust manifold, both O2 sensors, and the cam position sensor.
I'm sorry I dont remember all the codes I have. The code reader is at my father in-laws house.
However none of the codes were existant until that old exhaust broke. There were 4 codes: o2 sensor, catylitic converter, cam position sensor, and I think There was a heater control circuit code (no idea about that one).

 

I am thinking there is a recent thread where somebody talked about the exhaust breaking and melting the O2 harness.

 

If you get a chance, get the codes and post them here.

 

These are the codes I have:
po445, po​​​​031, po037, po340

 

P0340 is the camshaft position sensor. Replace that sensor (if not already) and clear the code. I did that to mine and all is well.

P0031 is related to the H02S Heater Control Circuit Low? Sensor 1 oxygen sensor malfunction?

P0037 – O2 Sensor? I seem to recall people experiencing bad O2 sensors… some people even called the dealership to see if they are covered. (up to 100k miles?) Possibly call if you are under 100k? This might be oxygen sensor 2 malfunction?

P0445 – Cannister purge valve

Almost like they are related. (ignition related)

Do you have any blown fuses? ECU may be upset that one of these components is not getting power before turning the key.

 

I've already replaced the CAM sensor and both of the O2 sensors.
However, I was unsure of the P0445 code and what that was. But funny you mention ignition because my ignition switch was starting to go and ironically completely went out yesterday so my car currently does not start. I've already ordered a new switch. But maybe that whole issue is causing that code to appear.

 

Did you replace the O2 sensors with the OE NTK branded sensors, part #25648? Non-NTK sensors (i.e., Bosch, others) are known to trip codes on the MINIs.

 

I basically got the cheapest aftermarket sensors on eBay haha so I recently learned that that won't fly. I just ordered 2 of the Bosch oem O2 sensors part # 13878.
Btw I replaced the ignition switch and my car starts every time now. However it still has this annoying hiccup when it tries to start. It's had that hiccup ever since all of these original problems took place.

 

Hmmmmmmm

How many miles on your JCW?

Fuel related now?

Fuel Tank Breather Valve - Part #: 13-90-7-572-086-M292 (check both connections leading to the valve?)
I believe there is a charcoal cannister as well for the fuel vapor???
Cleaning up the gas cap if it is dirty or dying?

Just spit balling here... Tough to say and you just dont want to start throwing parts at it.

 

My mini has 127,000 miles.
And yeah I've already been buying a bunch of parts for it and they have not been cheap haha. But I do wanna get her fixed up. It does sound as though it could be fuel related. Because after it hiccups and it starts, it runs perfectly. No signs of the rpms dropping at idle or while driving. It's got the lower like when I first bought it and it sounds normal.
I was thinking that maybe it's that CAM position sensor code that I have. I replaced the cam sensor but maybe I didn't spend enough money on that part -_-

 

Interesting... I recall having rough starts, weird idling WHEN I would first start my Mini each day. For a second or two, it would almost 'lope' like I had an aggressive cam in it and then idle would return to fine. Back in August 2016, I took the plunge and replaced the cam sensor and crank sensor as part of a large project I was doing. Since then, zero issues with funky/funny start ups and idling.

With replacing the cam sensor... did you clear the code? Ever since the distributor was removed (on newer cars), these two sensors need to be operating well in order to work together on the ignition timing of the motor. For me, one or both were starting to go south and no longer want to play nicely in the sandbox. And that was at 113,859 miles for me.