I just started noticing something on my MCS that I’ve never felt before. I noticed today that when I’m driving around town (30-40mph), on flat pavement with a light load on the motor (18-20hg vacuum)…I can feel a slight surging/bucking feeling. It’s so light that sometimes I’m not sure if it’s really doing it, or it’s just in my mind. I’ve noticed it enough now that I’m pretty sure it’s real…

If I’m going up a hill, down a hill, or accelerating at all…..everything’s fine. The car runs perfect, make great power, and everything is good…..except recently when I’ve started to notice the light surging on flat pavement at slow speeds. I’ve had the car for a few years, and never noticed this.



It almost feels like the motor is running lean…..feels like lean surging. I’ve tried running the engine up to 2500-3000 rpm in my garage and listening for any misfires, or anything strange….and it’s as smooth as could be. No surging or anything out of the ordinary. I’ve also checked the engine mounts, and that all looks good. I would think that if it was something like a fuel pump or fuel filter…it would run good during low rpm/low engine load…but start causing problems under high load/high rpm conditions…but that’s not the case. Same thing with plugs and wires….

The motor is all stock JCW.
Anyone have any ideas, or things I should check?

 

I know if I drive in too high a gear for the speed I am going....say 1800- 2200 rpm...I can feel it...I think it is the bypass valve partly opening/closing....
Simple fix...in a few more rpms...so shift.

 

Yeah, I know what that feels like....it's not the bypass valve. If it was the bypass valve i would be able to see the needle on the vac/boost gauge moving around...but its steady.The motor is not making any boost at all....it's pulling lots of vacuum. And I have tried running the rpm up, and as long as its under 3000 rpms I can feel it. It only does it while I'm maintaining a slow even speed on flat ground.

It's very lite surging, you really have to try to feel it.

 

dirty injectors ? belt tensioner problem ? throttle body ? Bypass valve. Those are the things I would check. Another thing might simply be to check battery, 1st gen. Mini's sometimes do weird crap when the battery is starting to go.

 

Depending on mileage you might want to consider your fuel filter. A dirty or clogged filter will do exactly what you are feeling.

 

sounds like a BPV, but any of the mentioned above are a possibility.

 

Thanks, I probably need to change it anyway. It's original, and I have around 115,000 miles on the car. Probably due for a change

I also dumped a can of seafoam in the tank, just for the heck of it.

By the way...who's got the best price on fuel filters?

 

Try pelican parts or ECS

 

Hey IQRaceworks... I have the same issue with my 2006 MCS. Any solutions? Any further updates? Would appreciate your insights!

briggswill

 

I think I have narrowed it down to slack in the drivetrain, not an actual motor issue. I think the bouncing around feeling I'm feeling, is from a loose or soft motor mount, allowing the engine to rock back and forth a little...causing the bouncing, surging feeling. I need to get under the car ASAP and see what I can find.

 

resurrection...

Did you every figure this one out??



.

 

Could also be a warped rear brake rotor. Fronts will vibrate while stopping, rears will pulsate at low speed.

 

I really doubt it was warped brakes.... Unless it was only happening when brakes were applied.... or they were SO horribly warped, you felt it ALL the time.

 

Did you ever get it sorted out??

 

@83K ('04 R53) - I had a similar situation. @4.2k - 5k rpms the Mini would surge - jerk intermittently. Recommended/suspected; the BPV. Instead of replacing the BPV I decided to try a few other things.
1) Replaced the OEM Plug wires w/blue NGK's (plugs were new). They helped. Mini idled and ran smoother. However, now @ lower rpms I could feel a slight surge.
2) Was suggested that it maybe a dirty or failing TMAP or Map sensor. Replaced the Map. Much improvement but not perfect.
3) Replaced the TMAP sensor. Success!!! - Mini ran like - well ....a MINI
4) I recently replaced my (never been changed), Fuel Filter... Wow what a difference!
Smooth Idle, great Throttle response from stop to 3.5k rpms and twisting 5.5k rpms @WOT in any gear.
No dumps, surging or jerks.

Hope this might help others as well.