We've owned our 2003 Cooper S, affectionately known as Grumpy, for about 3 years. All stock except for an aftermarket header (still has a stock main catalyst), exhaust, and a single mass clutch conversion. Currently at around 194,000 miles, IIRC. Service background in our ownership includes replacing the bypass valve, SC service, both oxygen sensors (NTK), fuel pump and fuel filter, spark plugs (correct NGK), plug wires, and ignition coil, and a new throttle body (original failed).

Last year around this time I started battling the dreaded p2096 code. Replaced the downstream O2 sensor at that time, ended up smoke testing and found a vacuum cap that had come off. At that time I also undid the "vacuum gain" mod for the BPV. Reset adaptations and got the CEL out and the car through emissions inspection. CEL remained out, but fuel mileage seemed down. At first I chalked it up to resetting the adaptations, but it's been at least 2,000 miles, now, and things haven't improved at all. And now there is the stumble/hesitation that occurs at part throttle cruise between 2k and 3k rpm. That prompted the tune-up including coil replacement, but no change. I've watched some data on my scan tool, thinking knock retard from a failing knock sensor, but the ignition timing looks good. Engine is quiet, no rattles from the timing chain area, etc. Balancer, belt, and belt tensioner have all been replaced. I've bounced this off a few people with no real results yet, so I'm asking the Mini gurus for help. Thanks in advance!

 

I'm in the process of rebuilding a 2003 R53. Earlier this month, I got the engine put back together with a rebuilt head. The balancer, timing chain, chain guides and tensioner are new as are just about every seal and gasket in the engine. I am experiencing a similar stumble -- sometimes at idle, sometimes at partial power. I still have to check for vacuum leaks. Based on other threads I've read, it seems that the MAP and TMAP sensors are also candidates. After that I'll be relying on the gurus as well.

 

Try turning off the DSC and see if that helps.

 

If it helps, does that indicate a bad wheel speed sensor?

 

Is there somewhere I can find what the MAP and TMAP sensors are supposed to read? Knowing what to look at is one thing, understanding what you're seeing when looking at it is the key.

 

MAP is manifold air pressure. The MAP sensor is located by the thermostat and has a plastic pipe (gray, if I remember correctly) that goes to the intake duct that runs between the throttle body and the supercharger inlet. It measures air pressure before the supercharger. The TMAP sensor is similar but also measures temperature. It is located on the intake manifold and measures air pressure after the supercharger.

 

Yes, I am well aware of what they are and where they are. What I want to know is what they should be reading when I look at them through my scan tool to tell if they are working properly.

 

Sorry, I didn't understand that's what you were asking. Perhaps someone else knows the values.

 

Sorry, my response was a bit harsh. Thanks for trying to help!

 

No worries. I did a search and found a helpful thread on one of the other Mini forums -- don't think I can link it here. The thread title is: ScanGauge gives odd MAP readings. The first few posts were helpful. PM me if you don't find the thread.

 

👍

 

Also avail in Bentley (the tmap and map readings)

 

Tried this, made no difference.

 

Also avail in Bentley

 

 

Thank you!

Now I just need to fix the cracked radiator so I can drive Grumpy and check this data.

 

So 6 months later I still haven't really looked into this too much more, I just haven't had time to data log, and such. I have been driving the car once a week and put around 120 miles on it that day. The fuel mileage actually seems to be about where it should be with the amount of highway driving I do those days. I'm able to manage 31 mpg if I'm being careful with my speed and throttle. I have noticed a lot of the time the car simply seems to lack power until around 3k rpm where it really wakes up and feels as it should. There's a serious bog when starting from a stop in 1st gear most of the time, too. If you don't use the right amount of rpm and slip the clutch a bit more it barely moves out.

 

Can you test the crank position sensor with an oscilloscope? Replacing the crank sensor and connector solved my stumble problem.

 

Not a bad thought. The E46s have crank sensor problems, but they split the casing and seep oil through the sensor into the harness. I did remove and inspect the crank sensor when I serviced the SC about 18 mos ago and everything looked OK. Would make sense as the tach does fluctuate with the stumble. Is it related to the cause or is it a result of the cause?