So after many hours of realizing how mini the room to work under the hood is I was finally able to install the Detroit tuned Bypass Valve, The Alta 15% reductiong pulley along with a new belt and the IK22 Iridium plugs from Denso. The first mod I had installed the Alta CAI. Also Have the one ball exhaust mod both of these have been done for a while now. Here is my experience so far and the problem I am having.

After the Alta intake and the One Ball mod

I noticed the Car while Idiling some times would start to stuble but not stall RPM's would fall to 500 to 700ish, it owuld not correct it self untill I gave it a litle gas. I also noticed that the Radiator fan would go off at random times.
But this stumbling would only happen rarely.


Next did the tune up and put the IK22 plugs and a week later Installed the Detroit Tuned Bypass Valve and the 15% reduction pulley, as well as the belt.

I noticed right off the bat the power gain, I did not notice the BPV really. I did test drive it in between and it did feel a bit snappier but not what I thought. I really though this would fix the stumbling problem since I contributed the stumbling to a failing BPV, but i was wrong. About the week later the stumbling was back, Although I had also installed the Pulley a couple hours later. so the stumbling persisted after both. Not sure what it could be now.


The other thing that I have noticed is the Flat Spot on which seems to appear from 2700-3300 rpm. not present if at full throttle. One big hint that something is up is when I stand on it on the freeway like to pass a car i start to here the valves slam shut. The flat spot is either getting worse or im noticing it more.


What should I be looking for? I like to think im mechanically inclinded, and I double checked my work. Did i not get the right plugs? Fueling? Vaccume? What Ideas do you guys have. I was thinking of doing the vgs mod, but not sure.

Thanks for all your help ahead of time.

 

Make sure you torqued those plugs, the Denso's are known for coming loose. I suggest the NGK's.

 

Excellent, Thank you. I will check that i have put about 500 miles since install I think I would have launched one buy now but i will check em! I have yet to replace the coil and coil wire so I wonder if that might be a contributing factor...

 

I have had the rough idle, dropping rpm off and on since I've had my MINI, regardless of mods I have made... I switched gas stations and the problem went away... Running 93 octane Shell fuel now...

 

Interesting, I too run shell exclusivley. I wonder if its time for some fuel system treatment. I was wondering on the way home right now that maybe the software on the car is not the most recent. I think this car was a garage queen as its and 03 and when I got it a year ago it only had 58k miles on it. I reset the computer after the mods, and im almost 100% certain that the flat spot did not appear until the pulley was done...

 

After a pulley a car does require more octane, so it is possible you are felling the timing getting retarded...with cooler temps this would not be expected with 93 octane....
It has been documented that a car with a 15% pulley will be running with retarted timing with 91 octane, or as the tester said, crappy Californina blends. You might be dealing with the yearly changeover to winter gas... The formulation changes to increase or decrease the vapor preasure of the fuel seasonly, and out mini's seem to be senseitive to the change...seems to take a few tanks of gas to relearn how to run on the new fuel.

 

The weird idle could be a small vacuum leak... but that would likely throw a code. I really wouldn't worry about that.

 

Im going to try some fuel system cleaner and then try another brand of fuel, I wonder who may have 93 here in San Diego, I also wonder what would happen if i changed the plugs to another step colder?

 

I have the same idle stumble as well since i purchased the car at 75k miles (completely stock). I use 93 octane and it doesn't seem to be effected by temperature (115*F to 40*F have shown the issue). I typically raise the RPM to about 3k for a couple of seconds and it goes away. I'm thinking about changing my fuel filter and plugs soon to see if this has an effect on the stumble.

 

Mine is an 04 w/48k miles. Only mod is DDM CAI. Even before the intake, mine would occasionally stumble/low idle - mostly after it's been running for a while. A quick blip on the throttle cures it.

I used to have an '85 BMW 318 i.s. and it did the same thing. Could just be a BMW thing?

As far as your flat spot, I think it could just be your tune. The stock tune is going to have flat spots in the power band. Many people have said once you get your MINI tuned, acceleration feels smooth from idle all the way to redline.

 

I think I am going to have to bite the bullet and have it tuned but I want to rule out as much as possible before I do that. Although one thing i found out today did scare me a bit. I went to re check the IK22 denso's I figured i would read them while i was out it. Well turns out they are a little too white for my liking. with 500 miles since the mods I would assume that the plugs should be a brown tan color in stead they are an off white. I also noticed tonight after standing on it to find the rice crispies is that they occur at wot just north of 4500rpm then they disappear, and then between 5200rpm and 6000rpm they disappear, then return I shut it down at 6250 as i dont see the need to go any higher. I am running some seafoam through it and on my next fill I will do a hard core fuel milage check since I am really starting to notice the mileage is down. To top it off I got my registration today and its time for smog... has anyone with a tune had issues with smog?

 

Mine did that after the same mods including the one-ball. Was not bad but I would be slightly worried it would die and not restart. Pulled the battery cable for a while and re-hooked up to reset the ECU. This seemed to help quite a bit but every now and then the issue would still show up.

A couple of months ago I went to leave work and the car started up in "limp" mode. After shutting down and re-starting and finally letting it sit for 5 minutes it started and ran fine but threw a code.

Took to the dealer the next day and ended up being a bad throttle body. Was replaced and since no more issues with the idle. They told me they never have to replace them but once in a while. What failed on mine was the IAT sensor. Unit is one-piece so they could not just out a new sensor in.

Might be something to at least check out.

 

All good recommendations here. Yes, do the fuel treatment. Besides Sea Foam, STP has a four-stage method of fuel treatment. Start with a bottle of the fuel injector cleaner (black in color). Then, about every 3,000 miles, use one of the STP fuel treatments (red in color).

Definitely check the battery terminals. The seal in my battery box went bad, and it was full of water by the time I went to the dealer to get it diagnosed. Both battery cables had to be replaced, as well as the primary 250A fuse box. Afterward, the battery terminals still appeared to be slightly corroded. I cleaned them up with a brass brush. You can also buy a spray bottle of terminal protectant.

The fuel filter is another good point. It should be change about every 50K miles. You can do it yourself. The filter is under the panel below the passenger side of the rear seat. Keep in mind you may have to reuse the original rubber seal. I've heard the one in the replacement kit may not fit properly.

As for fuel brands, the one I'm aware of for sure is Hess. Myself and a couple of other local club members had startup issues. My MINI would immediately die after starting. Start it again, and it was good for the day. I stopped using Hess gas, and the problem went away.

Yes, definitely make sure the plugs are tightened. If you have the stock coil, check the terminals to make sure there is no carbon buildup. #3 is notorious for this. Clean them with a brass brush and/or a can of STP carb spray cleaner and a shop rag. If you are using an aftermarket coil, especially the Screamin' Demon, change it back to stock. I've read other posts where MINI owners had spark issues. The stock coil is good up to 300 HP. Stock wires are fine, too. No need to really upgrade them.

Seals could be an issue. It's very common for the intercooler seals to not fully seat around the air horns. You can either use a white smoke source into the intake, or you can use a length of hose, hold one end to your ear, and run the other around the sealed areas to listen for leaks.

 

First off thank you all for your suggestions! I have discovered a few more things and came up with some theories let see what you guys think!

Symptoms:
Flat Spot 2800-3500rpm

Pinging under hard accel after some seafoam, is now almost gone but occurs slightly at wot just north of 4k then disappears and comes back at 5800rpm.

Fuel Mileage down around 20-23 mpg

Ik22 spark plugs read lean as they are pretty white after 500 miles.

Cold start in the AM car takes a second to start.

Runs good before heat soak

So those are the symptoms...

Here is my new theory.
Map Sensor dirty from oily residue found in plastic tube that the throttle body mounts on. I believe it came from the Uni Air Filter oil. So ECM does not know true boost so it runs motor a little lean thinking its not as much boost. Could have been present before pulley but after pulley problem gets worst becuase of higher pressure.

Second theory.

Pre Cat 02 Sensor is ready to be replaced, contamination could be making the voltage lower making the car think that it is running rich and correcting as such.


THe thing that gets me are plugs read Lean, and fuel mileage is down. To me those are opposite symptoms...right?

 

Just got home and put it on the code scanner and no codes found! Im waiting for it to cool off so I can clean the T-MAP and MAP sensors I will be installing a brand new set of stock plugs tomorrow just to see what happens.

 

Hmm... if your mileage is that low, you should technically be running overly rich. Since you are running lean, I highly recommend no WOT driving. The ECU changes fuel mappings when you do that, and it also ignores the readings from the MAP and O2 sensors. So long as you stay < 80% pedal, the regular fuel map should make the effort to maintain a 14.7:1 air/fuel ratio.

If any of the seals are not properly seated, you could be getting more air than fuel, which is messing around with the O2 sensors. Check and verify the vacuum line from the back left of the intake manifold (near the passenger-side air horn) is properly seated, as well as the other end at the MAP sensor under the intercooler in between the intake runners. Also check and make sure the vacuum line leading to the fuel rail idle bulb is seated properly.

 

Thanks Flash! Well I got around to changing the o2 sensor today, the entire tip was white indicative of a o2 sensor that is contaminated. I replaced it with the NTK one, also checked for vacuume leaks again reset the computer and now i think im going for a road test. I also check the gap on the plugs and now the plugs are starting to look better this last 1/4 tank i ran sea foam through it and im thinking i might be getting close. If the problem persists im going to tackle the fuel system I replaced the pump and filter about 10k miles ago so i doubt its that.

 

well I today was a good day I nailed it down to the hesitation i was feeling occurs between 3-4k, I tried to the best to describe it to a friend and suddenly the word came out... Yo Yo... So just now I finished up doing the VGS mod I did it from the nipple on the intake plenum. I discovered something scary, the vacuume line that normally goes there was barely holding on and at that was very loose... i mean no big deal, all it does is provide the Vacuume for the Fuel Pressure regulator LOL So Im headed to the gas station to fill up and reset the computer one more time... lets see how it goes!

 

I am also experiencing the same hesitation between 3-4K RPM. Did you ever figure out the hesitation problem? I just finished doing the Valeo Clutch kit replacement and also installed the Detroit BPV, since I was also experiencing the yo yo effect. All works well, except for the hesitation between 3-4K RPM.

 

I had this issue even after replacing the bypass valve with an OEM replacement. I had an old BPV from another car lying around. I compared the spring tension and the new replacement had less tension than the used part. I swapped parts on the car. There is still a very slight yoyo, almost so slight I wouldn't know it was there if I didn't have a vacuum/boost gauge to watch the needle bounce. It was pretty annoying before when at aggressive part throttle and 3-4K RPM.

So if any of you are having this issue even after swapping the BPV, you might want to get a used part or something and compare the spring resistance, or get a Detroit Tuned valve.
If you still have yo-yo after all that, look for a vacuum leak, especially post-supercharger - you could have cracked intercooler boots for example.