Ok so our 05 mini JCW (210 kit) just started having a bit of a cold start problem a week ago along with sputter with light revs. It will usually have a tough time starting the first try but lights up on the second try. If you drive it, it feels fine and if you rev it normal it feels fine. Just those light revs sputter and choke.

Yesterday I replaced the belt because the old one was slick on the back along with a new tensioner and a new fuel filter. 5k to 8k miles ago the previous owner installed a screamin demon coil pack, live wire spark plug wires and went with the stock NGK BKR7EQUP plugs which already seem to look dirty. I didn't replace the plugs just checked to make sure they were still torqued to 20 ft lb.

I also have the amsoil air filter that's brand new so I know there's no problem there. Is this the "summer gasoline" problem I'm seeing people talk about?

Just discovered the vacuum line going into the intake box was disconnected under the intercooler so I removed it the intercooler plugged the hose back it was a "this has to be it" sort of hope, put it all back together... And nothing changed. Maybe this is just normal or I maybe need to looking into the iridium spark plugs?

Ok so it looks like it was the vacuum leak that was causing the crappy revs. I just threw a plug on the line that goes to the JCW airbox since I did the flap mod on it and that seems to have solved it

So I took the car for a somewhat spirited drive to the store 3 minutes away. I wasn't beating it to the ground but I did a couple gears to 5.5k rpms. Then when I pulled into the parking lot it chugged a little after I came to a stop then leveled out. Then I drove it home, another three minutes not going over 4.5k rpms. By the time I got home the check engine light had come on. So I checked my work from the past couple days. The belt looked fine and was moving nicely, the tensioner wasn't bouncing around like it was, the air box was tight as well and the intake hose, and the vacuum lines were still connected with the line to the intake still plugged. So then I pulled the spark plug wires and all needed slight force except cylinder 3. So I seated them all back down but cyclindar three never "clicked". They're live wire plugs so I don't know if they're known for that but I put some dielectric grease on it and still no luck on getting it to click.

I went to advanced auto to have the code scanned but apparently, as of June 5th, they don't do that anymore.

So I'll have to get it scanned tomorrow. If it comes out as a misfire on cyclindar 3 I will know why and switch out these wires.

Other than that the car seems to be running smoother at stop lights and has more pick up.

Interesting - I'm new to my R53 and it did that low-rpm stutter from day one. Start cold, pulse the throttle and it coughs before revving up.

I wasn't sure if it was the nature of the beast or something was wrong. I'll let you know if I find anything, and I'm eagerly anticipating any results from your car

I'll be checking the code tomorrow. If it's a misfire in cylinder 3 then I'm almost positive it's the spark plug wire that won't seat.

Definitely get the code read, I read a thread about cold start problems and it turned out to be a warped head. Has the car had any overheating episodes?

Seems too sudden to be anything like that but I'll check it out.

Alright, just got home from pepboys and the code is p1237 "malfunctioning controlled fuel and air metering". So I'll check the vacuum lines from yesterday. Might take that plug off and just replug it into the airbox.

Yes u look at the ignition coil....it corrodes ..
And imo vet a $45 set of standard 10mm wires...
Sell the gimikiy things....

Got it. The vacuum line between the bypass valve and the "T" that went to the airbox was super hard and sliding off the bypass valve nipple. So I went to the parts store and picked up some new vacuum line, installed it in place of the hard tubing. Cleared the code and drove at variable speeds for about 20 minutes and everything seems to be running good. I'll be interested to see how it affects the start up tomorrow. I'm guessing it will probably fix it since the bypass valve will be able to react properly at start up

Cold start was better this morning but still took two tries. Next I'm going to replace the negative battery cable because it's showing some wear.

Should I buy a new cable or make one?

This morning, turned the ignition to the on position, waited a few seconds, and it fired right up.

OK so if I wait for all the checks to be done (indicated by the fuel gauge going from red to orange) it fires right up every time.

Been watching this thread. Did you consider that it's maybe the fuel pressure building up (and not the system check) that's making a difference in cold-starts?

Also, it's good of you to come back and report on you progress and solutions.

Yea that would make sense about the fuel pressure. No problem. I just know how frustrating it was when I was searching for answers and all the threads lead to nothing

So what change made the most noticeable difference? I'm also getting the sputtering noise at cold start in my JCW.

Just waiting for the red light on my fuel gauge to turn orange before starting it. Takes about 5-7 seconds