I'm having hesitation on acceleration. It's generally less pronounced at higher (4k+ rpms) and appears in the 2k-3.5k range depending on the gear you're in. Even at higher rpms though I can tell it's not right and has little "blips" in performance. I could be at 70 mph on the freeway just coasting and give it just a little throttle (say to speed up to 75) and feel it hesitating or I could experience it just trying to accelerate through the gears. Car idles perfectly fine around the ~700rpm range. In summary, it's not fun to drive like this!

Only things installed when this started happening were Alta CAI, WMW 15% pulley and new belt + 1 range colder plugs. Noticed it shortly after pulley install but seems to have gotten worse within the last month or so.

Car is 2006 MCS with ~74k on the odo.

Here's a list of things we've checked/tried/replaced:
-checked sc reduction pulley and belt- replaced belt just in case but no signs of wear or slippage and pulley was installed correctly.
-DTBPV was installed and has also been tested with BPV disconnected and issue persists
-No sign of fouling on plugs but still tried new colder plugs as well as the stock (warmer) plugs.
-Replaced coil pack and HT leads with what's in my signature
-system showed no codes; reset ECM and code for T-MAP sensor error appeared- we replaced T-MAP sensor yesterday but hesitation persists (I don't know how to describe its location except that it was NOT the one right behind the upper radiator hose by the bleed screw)
-boost measured at ~15 PSI
-Fuel pressure was good (and tested under throttle)
-oil recently changed

We're officially stumped- any ideas?

I was going to Seafoam it through the PCV tomorrow just for the hell of it.

Thanks!

 

Could it be carbon buildup on the intake valves? Have they ever been cleaned? If the carbon buildup is real bad, you might need to have the walnut shell blasting treatment.

 

I know I'm at 74k miles, but would that be normal for a 1st gen? I thought the 2nd gen had this issue because of the location of the fuel injectors and/or something to do with the HPFP.

Maybe the Seafoam would help if this was the case? Oh, and for what it's worth I go WOT all the time.

 

Yeah, you are right. The direct injection engines mainly have the problem. It does sound like something is gunked up. You might want to try some BG 44k. I'm going to be using it to try and keep my 2012 CMS cleaned out.

 

Was just reading another thread about a disconnected hose and went to see how mine were hooked up as a reference and actually found something disconnected on my car.

Any idea what this is?

 

It was a pain in the *** to get to but I reconnected that little hose and took the car out. It was immediately awesome to drive again. However... a few minutes in, the hesitation started back up and my immediate thought was the hose had come off again. Sure enough, when I got back home and looked, it had popped off!

Should I try to zip-tie it for the time being?

I guess the bigger question is why did it come off- just old rubber? Anyone know what part this is and where to get a better one?

 

If this is the vacuum hose that connects the bottom of the FPR to the underside of the inlet horn, then replace this IMMEDIATELY! Go to any auto part store and ask for blue (more visible color) or black silicon hose that is typically used to connect to boost gauge. Then use zip tie to secure BOTH ends.

 

I will have to check mine! I've been having a similar problem.

 

I'm pretty sure it is one some mech. gauges like Alta's tap into. It has a larger rubber nipple thing on one end and the metal offshoot it connects to like pictured. It's not the hard plastic once which often breaks- I inspected that one and it looks alright. I definitely want to fix it asap but what's the immediate threat- I mean it's been popped off for like 3 months.

Also, can I just zip-tie the existing line in place until I can get a new one? It's not like it's leaking- it's just popping off completely.

Check and let me know for sure!

 

How did you get to see that? Or, what did you need to remove?

 

Didn't remove anything- just used a flashlight and looked back there. When reconnecting it i pulled one of the more flexible hoses out of the way but didn't disconnect anything else. I suspect removing the intercooler would be the easiest way to replace this and/or zip tie it for the time being. I'll get to that this afternoon.

I posed a picture above which shows exactly where this is on the car.

 

Update- took off the intercooler this morning to gain better access. I then zip tied it back on (actually used two zip ties- a smaller and a larger one next to one another). Hardest part one reassembling it was just making sure I didn't pinch the IC boots.

Did the ECU reset from the dash and took it out for a crazy ride with lots of WOT. Car was crazy fast and when I got back I checked the connection and it hadn't budged.

So... if you have crazy hesitation and have tried everything else- check this line on the intake manifold to in case.

 

Good thing you found it, the only way your car can adjust how much fuel pressure it puts into the engine is through that vacuum line. I would strongly suggest getting a boost guage with vacuum. You could have spotted the problem the second it happened.

 

The ECU/DME can't be reset through the dash cluster, but glad you found the issue

 

Actually it can be, do a little research and you'll find the walkthrough just like I did after first reading that the OP did it

 

I am familiar with the procedure you are referring to, and it does not reset the DME/ECU...it is just a cluster/instruments reset.
Resetting the adaptations in the DME can only be done through ISID now, as the GT1 is somewhat outdated.

 

Well, link me to one you'd recommend. Boost was 15PSI when they measured it even with this problem occurring.

 

It's not the boost (or lack of) that would have tipped you off, but rather the lack of vacuum. At idle, in neutral and with the A/C off and a warm engine you should pull about 17 inches of murcury (~ 8.5 psi) below ambient. With the car off it should be zero as shown in the guage attached below.

http://www.mellonracing.com/images/A...st%20gauge.jpg

Anything above 15 (closer to zero) should raise an eyebrow.

 

I've been having the exact same issue. I've had my mini for a year now with no idea what's been maintained by previous owner. We changed everything imaginable to fix the issue.
Following what you said- we checked it and it wasn't totally sealing it airtight. Got it securely zip tied and now it's running way better.

 

Wow UScooper thanks buddy you are a life saver solved my problem on my MCS 2006. This is the ultimate fix along with a new BPCV. For all of us with hesitation and performance limp mode problems once plugs leads, and Tmap / map sensor have been replaced. As was my issues and your find and share was the ultimate fix. Big thank you from sunny Capetown

 

Wow! Thank you USCooper! I've been having a vacuum leak for 3 months that I've not been able to track down. Kept getting an intermittent CEL code p1498 and EML light that would throw the car into limp mode for a day then disappear.

That picture you posted lead me to the exact same problem on my car. The little rubber boot on the end of the vacuum line seems to relax a little bit and let go, I zip tied it back on and immediately the idle has calmed down and the car has stopped hesitating and tripping over itself on acceleration.

 

Fully appreciate and understand that the last reply was over 2 years ago! But I would just like to say a big thank you to USCooper - this pipe was disconnected on mine, and after scratching my head for nearly 6 months, I got a 19% pulley fitted in the hope of making things better.... which it didn't!

Turns out this pipe was disconnected!

Popped them back together, went out for a quick drive and WOW the car is night and day different.
Thank you so much for your postings on this thread all those years ago!!
I have no idea if you are still a member here or even own a Mini anymore, but you have fixed my problem!

 

Glad this thread is still helping people! I know it was a big relief when I figured it out and made the car a lot more fun to drive again. F80 M3 owner now but will always have a place in my heart and garage for Gen1 MINIs.

 

Old threads never die here they that just wait around until another MINI owner needs some help figuring something out. This is what makes a car forum so much different from FB, you can find old posts.

For me, the little brother is more fun than the bigger brother . . . . .

 

:D You've brought my lovely R52 JCW back to life!
Had a 19% pulley fitted before Christmas and I just knew something wasn't right. My other R53 JCW felt so much quicker (and is completely stock) and its taken me from then to figure out what it was! You have no idea how many forums I've read, blog posts, phonecalls to mini specialists, hours of ramp time etc etc - and it was this simple thing all along!

Thank you again!