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  #1  
Old 02-25-2012, 05:58 PM
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Default Stuttering/Sputtering when hard acceleration - and now Engine Light

My 05 MCS stutters when I really get on the throttle, sounds like its choking, not getting enough air or running too lean. However these are just guesses. I've lived with it for quite some time as if I am tame with the throttle I don't experience this, only when jamming the pedal down quickly.

This morning however I was on the highway in 6th and had to slow down due to being cut off - I must have been at 50mph. I didn't shift out of 6th and changed lanes to go around. I wasn't in a rush nor pissed so just gave the car some gas and it started sputtering like mad, engine light goes on, traction control light goes on, and engine suddenly sounds like a diesel and has very little power - doesn't want to be pushed at all. I'm guessing this is the famed limp mode I've read about?

So I throw on hazard lights and pull over to the shoulder. Turn the car off, throw my head under the hood, just looking for anything obviously wrong and smelling. Nothing. Sit and talk to my wife for 2-3 minutes, and turn the car back on. Traction light is off, engine sounds healthy again, and off we go - drove w/o radio listening for anything that would throw me a clue as to what the hell that was all about. Nothing. Engine light is still on as I obviously threw a code.

Just curious what you more experienced guys think may be going on?

05 MCS
- 17% pulley
- NKG 1 step plugs
- JCW 380s
- JCW airbox
- JCW tune
- 1-ball exhaust

Much appreciated.
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Old 02-26-2012, 02:20 PM
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It sounds a lot like misfiring to me, but that's too vague to pinpoint anything specific. How old are your spark plugs? Same thing happened on mine with similar mods and it was just the plugs. Might be worth it to pull them and see how they look, but getting a reading on the fault codes will help you immensely.
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Old 02-26-2012, 02:41 PM
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Also check for boost leaks. My car had similar symptoms. Replacing the aftermarket intercooler couplers with the stock ones fixed mine.
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Old 02-26-2012, 02:44 PM
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Map sensor or coil pack?
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Old 02-26-2012, 03:29 PM
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I just had this EXACT same thing happen to me as well. I also thought it was a boost leak but it turned out it was a dirty fuel injector. I had a bad batch of Shell V-Power. It turned out all the car needed was for the injector to be cleaned physically and fuel injector cleaner to be applied afterwards
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Old 02-26-2012, 04:10 PM
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sounds like the plug maybe. My r53 did that when i had the screamin demon coil
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Old 02-26-2012, 06:50 PM
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check coil pack, plug wires, and plugs first for corrosion.
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Old 02-26-2012, 09:04 PM
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Hey Guys thanks - I'm at work again today so can't do much to take a look right now. I poke around the car but am not a mechanic by any means, so if anything I am saying below is wrong please call me out. Always looking to learn something.

Interestingly enough I grabbed a video of this stutter about 2-3 weeks ago, wanting to post it here.
It's just from an iPhone - you can hear the supercharger kinda skipping - a stutter is felt throughout the car when this happens.

https://vimeo.com/37481439

Don't ask me what the hell I'm saying after 'and go'

I bought the car in May 2010. Had the 17% pulley done then. Winter of 2010 did the NGK plugs. Fall of 2011 did the JCW fuel Injectors, JCW Airbox, and replaced the fuel filter. The coil pack and wires are OEM. The car has 112k miles on it now. If it was the plugs, pack, or wires, wouldn't I get missfires throughout driving? The car did this even before the injectors, airbox, and fuel filter were replaced. I was hoping that one of them would take care of it but nothing changed. Sadly I do not have a boost gauge.

I've been poking around and some say it could be the BPV or the rubber IC boots leaking boost?

I need to get this code read - will have to look to see what's around work here. I've heard autozone and/or napa will read codes?

Much thanks, will keep updating the thread here.
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Old 02-26-2012, 10:36 PM
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pull off #3 wire on the coil pack, takes a little umph. all of them since you're checking it anyway, do one at a time so you don't get the firing order mixed up. i have a feeling the pack and the wire will be corroded. it's the easiest of all your possible issues to check, no tools required

the code will probably say "cylinder #? misfire"

autozone will do it for you, quick plug in and read.
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Old 02-26-2012, 11:02 PM
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yes, good call to check each plug. I did it the other way around -- I pulled the plugs out from the motor side of the wire, and found out it was my cylinder 2 that was dead until I cleaned it out.
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Old 02-27-2012, 02:34 PM
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I had the same symptoms a while back, turned out my harmonic balancer had split in half and with more than half throttle it would spin on itself. sputtering, stalling, and limp mode.

when we got it off the car it just fell apart...
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Old 02-27-2012, 10:46 PM
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Checked the coil pack last night. 1,2, &4 contacts were shiny clean. 3 was a little corroded. Just light rust here and there. Not caked, not covered, just bits. Just a matter of scouring this off or is it new coil pack time? (will wait for code) Just rubbed my finger around the contact last night - by no means a thorough cleaning job.

My question again - please help me understand - if it was in fact an issue with the coil pack, wires, or plugs, wouldn't I be feeling this all the time?

So we're up to:
  1. plugs
  2. pack
  3. wires
  4. bpv
  5. ic boots
  6. fuel injector - as mentioned had the issue even before the JCW 380s went in so I'm skeptical with this one.
  7. harmonic balancer

Going to get the code read by a buddy in the area, just waiting to hear about his schedule.
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Old 02-27-2012, 11:20 PM
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wire brush that corrosion off you may solve your issue I had something similar happen and #3 had corrosion on #3 on the coil itself. A little clean up and some dielectric grease (electrical contact lube) and no issues.
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  #14  
Old 02-27-2012, 11:22 PM
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When my coil pack was messed up it didnt go into limp mode all the time. Then finally like 2 months later it went in permanently. Found out later it was when i plugged it up to the harness some of the connectors got bent and then fried my computer and harness.
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  #15  
Old 02-28-2012, 01:09 PM
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Cleaned off the #3 contact on the coil pack and added some dielectric grease. Problem still there this morning on the drive to work.
Mind you this isn't happening during normal driving, just if I really get on it without much easing down on the gas.
Just want to know what the heck it is - honestly glad that the code was thrown. Getting it read tonight.
Thanks for the help guys.
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