I had my mini serviced by my friend a few weeks ago, and since then it's been sluggish in accelerating...it's kinda missing that "oomph." It's an 04 R53 with 97k.

What he changed was the radiator (it had a leak), crank sensor o-ring, supercharger oil + gaskets, and the thermostat (the main reason it was being serviced). I also bought a new supercharger (serpentine) belt, which was oem.

This is the belt I bought:

http://www.ecstuning.com/ES21735/

I'm thinking this is the problem, but I've read that it could be the clutch (doubt it) or even the Bypass valve (maybe).

What do you guys think?

Thanks in advance!

 

You didn't mention it, but did he replace your spark plugs, or service your air filter?

I ask because I had worked on a R53 awhile ago that was sluggish running and it turned out to be the wrong spark plugs, and just for fun I checked the air filter housing and I found a shop rag. I removed the shop rag, and ran it better but still not the way should be so I put in the correct plugs and it was running like champ.

Motor on!

 

Any engine mods on the car, such as a supercharger pulley?
Any Check Engine Soon lights? If so what code?

 

The bypass valve has a spring AND a vacume line...maybe the vac line was not hooked up right?
Anyway...you can test if it is the bypass valve with a zip tie...wire it open or shut for a drive...see if the car gets better or worse...

 

JABowders: He didn't replace any spark plugs. I probably have to clean my intake filter soon, since it's getting pretty close to 10k miles.

quikmini: The only engine mod I have is a cold air intake. I actually just cleared a check engine light about a week or two ago. It was because of the thermostat and I needed to get my car smogged.

ZippyNH: Where is it located? I've been wanting to change it soon anyways since I'm at 97k and have an 04 mini. Sometimes the yo-yoing is really annoying

I also took a drive today. Seemed normal at times and others it was slow to accelerate...kinda weird. I did here this ticking sound when I was at a stop light. I'm thinking that sound is the timing chain and the tensioner is stuck (as I've heard this happens). I only hear it from time to time.

Also experienced this weird shaking my engine does. It's like a pulse... I've felt it do this a handful of times the past few years and it happened again today. It only happens when I'm stopped at a stop light and it goes away the next time I'm stopped.