Hi there I wonder if anyone can help me.


I have an automatic mini cooper s 2005. I bought the car with no issues (31,000 miles).
I then had the pulley kit professionally installed, 17% reduced pulley, correct belt and cooler plugs.
While the car felt quicker I was left with a very annoying hesitation (pause in power) for a second or sometimes two at 4000rpm. started at say 3800rpm till 4200rpm and then full power would resume, comes in with a kick! I will note that this only happens on full throttle in gear (not auto kick down).


I have since done the one ball exhaust mod, fitted a sports manifold and cat, K&N panel filter and had a tune performed on a rolling road. I was hoping that the tune would rectify this hesitation issue but it did not.


I have also just fitted a brand new stock bypass valve thinking this may have been the problem but the hesitation still remains.


Any suggestions or help would be great.


Could this be an auto box restriction issue?


I live in the UK and there are few automatics over here.


Cheers Zach

 

Could be bypass valve, or an ignition issue. Happens a lot after a pulley change.

 

Check your plug wires and coil, especially the #3 wire and post. Also, check your MAP sensor to see if it needs cleaning.

How's your belt tensioner? Maybe your belt is slipping.

 

I have just checked the wires and coils, all seem to be like new, no corrosion at all.
the hesitation started the instant i drove the car after the pulley kit was fitted, its not something that happened over time or got worse, its stayed the same. Possible happened at slightly different rpms (within 200 rpms) with each additional mod. The tensioner would have been checked by the garage who fitted the pulley kit, they fit them all the time.
Is it possible then that this could be the map sensor? With such low miles and that it only happens at that exact rpm, its not randon.

 

Well I doubt it's the map sensor or you would have a code for it,

 

Yes thats what i thought. But i have no fault codes. Could it be the torque limiter for the auto box? 4000rpm must be close to peak torque. Could it be the gearbox map/software holding back?

 

I also have an auto and it pulls smoothly up to the redline. For reference, 15% pulley, JCW, exhaust, airbox, plugs, and tune, regular S head and intercooler, 91 octane CA gas w/ 10% ethanol. If we had 93 octane I would have gone with a 17% pulley.

Can you post a video of the issue?

 

Thats interesting, so its probably nothing to do with being auto. I run 95 ron usually, but now and then use 99 ron, the mini likes it, i can feel the benfit in power but i think it makes the hesitation slightly more. I think a video would be a good idea, i will upload as soon as i get a chance

 

Had this with my 05. Replaced the coil pack and leads. problem went away.

https://www.northamericanmotoring.com/forums/r50-r53-hatch-talk-2002-2006/284254-05-r53-hesitation-2k-3k-rpm.html

heres my post, read through it and watch the video, see if its similar for you.