This Is my first post as I am very new to both the forum and the world of mini coopers as well. Recently my 2004 manual cooper s had gotten work done to fix the steering column, axle, and control arm on the front right side of the car after meeting a curb. I got the car back last night and as I was leaving the garage that worked on it I gave it a bit of throttle and at first I was confused because it was just slow and then it popped up a cel light and went into limp mode. I pulled over and the garage mechanic came to meet me. He plugged his obd scanner in and got the error codes: p1688 and p0341. I've spent the entire morning messing with it. Its important to know that I had done a 17% pulley reduction and a K&N Cold air intake before the accident and everything ran fine. The first thing I checked was the Bypass valve and it seemed good. I don't exactly know the best way to check it however it had decent pressure when manually pushing the actuator and opened and closed based on the throttle when out of gear. I also zipp tied it at one point as well(something I read online) and there was no regain of power. I am aware that its possible the crank pulley is out of whack as I've seen lots of stuff with p1688 having to do with that and then with the addition of the p0341 which is a crank position reading thats kinda goofy that is what I am fearing. So I didn't know if there is a way to check the crank pulley without straight up replacing it? Im on a very tight budget so I need to be sure of whats wrong before purchasing any new parts. Or if there were any other possibilities as to the cause? If I keep the car in neutral and give it a good rev it will either go into limp mode again or sometimes it doesn't go into limp mode but as it reaches low rpms again it is very out of sink and shaky. We thought it was also possible that the injectors were a bit clogged maybe it was running lean after having sat for a few days however I put some injector cleaner in with a full tank of gas and there is no difference. It is currently drivable but it needs to accelerate really slow or else it will go limp and I have to restart. The engine also vibrates a lot because after the accident a small black piece of plastic ended up inside the pulley tensioner spring and it bounces a lot however I didn't think that would cause limpness. I also went ahead and reset the eco which didn't help either. Sorry for the rather out of order post but just hoping someone could help?

 

My bet is on a failing crank pulley/harmonic balancer. You might be able to check it by releasing the belt tensioner (so that there is no belt tension on the crank pulley), removing the passenger side wheel, and reach in to see if you can turn the pulley by hand (see if it “slips”). It may not have failed to the degree that you can hand turn it by hand yet, so no promises that this method will tell you it’s failing for sure. The stock pulley has an inner and outer metal part with rubber in between. When the rubber fails, the two parts kind of spin freely under engine torque.....then it comes flying apart eventually. You don’t want that to happen.

It’s not that hard to replace. I’ve replaced them on two cars I’ve owned as preventative measures.....first with the ATI superdamper type....and on my current car used the PRW fluid filled type. They are both very high quality....but the PRW is significantly less expensive, fwiw.

Hope that helps. Good luck.

 

See answer above as the crank pulley is very important and you do not want it to fail while driving.

That was the first thing I thought of when reading your post.