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Old 05-01-2012, 05:20 AM   #1
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Rough Idling @ Cold Start & Random Misfire Issues

Hi guys, need some advice. Trying to figure out what's causing this old reliable 02MCS to act up this past week. It's got 44k mi & lone K&N Typhoon CAI mod on it. Regularly serviced (every 5k)& well taken care of. Plugs, coil, wires,harmonic balancer are all stock & never changed yet though. Engine has never used up oil, never had to top it.
These are the issues I've noticed:

!. It starts instantly every morning but stumbles a coupla times before idle stabilizes as temp rises.
2. Random DSC & SES PO300 fault code but car runs smooth upon reaching operating temp
3. After car sits 5-10mins, it takes a coupla cranks longer to start w/ a slight stench of fuel=>rich. Always starts on 1st try though. Changed the coolant temp sensor on cylinder head, new belt, recharged the K&N CAI & cleaned the corroded #3 coil a coupla days ago, no improvement detected. Changed both strut mounts too. Huge difference there!
4. At operating temp, idle is stable @ 800. Random faint pop & burble can be sensed.

Need your inputs on possible causes & where I should start.
-Bad gas? Been running ethanol free premium gas. Might be a bad fill up? I'm trying to consume this tank & refill from another station next.
-Signs of failing harmonic damper? Don't hear noises & visually, it still looks ok. Which is best? PRW or ATI?
-vacuum leaks?
-plugs, coil, wires?

Hope to get it back to how it used to be. I'm crossing my fingers this is nothing serious. Maybe Khuevo could chime in? This forum has kept this mini in tip top shape all these years & I'm overly appreciative. Thanks, guys!
Happy motorin' & more power!
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Old 05-01-2012, 05:48 AM   #2
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Wow, that's low mileage for an '02. First off, I'd throw in a can of redline fuel system cleaner and give it the italian tune up. See if that helps, it often does.
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Old 05-01-2012, 06:08 AM   #3
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Quote:
Originally Posted by minsanity View Post
2. Random DSC & SES PO300 fault code but car runs smooth upon reaching operating temp
P0300 = random/multiple cylinder misfire. Most likely: 1.plugs 2.ignition wires 3.coil 4.cylinder/valve carbon build up.
Advice above is good advice. I would say: 1. change plugs 2. redline or SEAFOAM in the gas tank and through the intake(see our MA threads on Seafoam) at operating temp followed by Italian(spirited 30min highway acceleration and sustained speed) tune up.

Jason
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Old 05-01-2012, 11:32 AM   #4
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Quote:
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...Plugs, coil, wires,harmonic balancer are all stock & never changed...Random DSC & SES PO300 fault code but car runs smooth upon reaching operating temp...Might be a bad fill up?...-Signs of failing harmonic damper?...
Because of the low mileage over a ten year period, I'm sure there is moisture accumulation in the fuel tank, and this could be part of the problem. Fueling after or during a station's storage fill could produce similar symptoms. Regardless, the first thing I would do is replace the spark plug wires with new OEM.

A DSC code is a separate issue probably not connected to misfires.

If you're not seeing a P1688, battery lamp, or overheating, then probably not the crankshaft vibration damper or belt. Idle is seldom affected with those failures. Although, if the belt has never been replaced I would change it due to possible oxidation, and try wiggling the damper while you're at it.
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Old 05-01-2012, 11:37 AM   #5
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Thanks for your replies, guys! I definitely welcome & would try all sound suggestions by elimination. Keep em comin'. Anyone tried similar symptoms? Kinda annoying at start up. Strange thing is cold start up turns engine instanly but gets a minute of rough idling, while when warm, engine turns after a bit of longer cranking but idles well. Hmmm. Thought my coolant temp sensor was shot, hence the replacement. Off to trying advices....Thanks!
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Old 05-01-2012, 12:10 PM   #6
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Thanks for chiming right in K-huevo. Really admire the work you do!

When Belt was replaced a coupla days ago, it still looked good, though thinner, of course. Have'nt seen 1688 & tried wiggling & turning the damper. Seemed good w/ no visible cracks. No overheating. Is PRW as good as ATI?

1 habit of mine is to fill up when it isn't too hot out to get denser fuel. Dunno if that compunds more moisture into the tank. Would consuming this tank to maybe 1/4 level & refiiling from a different station be a logical approach? I'll definitely replace plugs. DSC lights up more often than SES when engine stumbles, but not everytime. Toggle can't switch it off. It turns off after every engine restart restart though. Any ideas on longer cranking issue when engine's warm?

Aside from Seafoam & Redline, what other cleaner/booster brands would you recommend?

Apologies for such a long post. Hoping to be enlightened. Thanks tons!
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Old 05-01-2012, 01:10 PM   #7
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I've had very good luck with Techron over the years.
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Old 05-01-2012, 01:42 PM   #8
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I use and recommend FP60.

First replace the spark plug wires with new OEM, and provide an update afterward.
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Old 05-01-2012, 01:54 PM   #9
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Ditto Keith's spark plug wires recommendation. Numerous times over the past 112k miles, I've had weird misfire issues. It almost always comes down to wires or corroded terminals in my cases.
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Old 05-01-2012, 02:39 PM   #10
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Quote:
Originally Posted by minsanity View Post
...Any ideas on longer cranking issue when engine's warm?...
I experience this each year around this time when summer blends are introduced. You're using ethanol free fuel so this shouldn't apply.

If you're not sure the ECU has the latest MINI program installed, I would look into an update.
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