Changed Spark Plugs, now rough/inconsistent idle...Help!

osukf09 · 04-07-2012, 03:47 PM

Just changed my spark plugs with the Bosch replacement plugs. Did all 6 plugs, started the car up, and the rpm's are very inconsistent and its a very rough idle. Definitely the exact opposite of what I was expecting! Can anyone diagnose something that I may have done wrong here? Install was pretty straight forward, or so I thought...

Note, I didn't put the engine cover back on or the cowl, filter, etc. as I wanted to start the car first. I've done JB4 install with no issue, and it's currently set on map 5. Should I try setting it to map 0 to see if the idle changes? I don't even want to drive the car with how bad the idle is right now...

Any quick help is very much appreciated! Thanks guys

Fred_Boosted · 04-07-2012, 04:04 PM

Yeah, set back to map 0 to see what happen.

Are you sure you bought right plugs?

osukf09 · 04-07-2012, 04:10 PM

Pretty sure, they've been mentioned in quite a few posts on here:

Bosch OE plug, ZGR6STE2

I checked the old plugs and they had the same part # so I'm assuming they're correct.

Just checked for codes and saw these new ones pop up:

2D2E- angle of throttle valve - intake pipe under pressure, correlation
29CD - Misfirings, Cylinder 1

I'm going to take out the plug for cylinder 1 and reinstall and see if that works. Both of these codes are brand new after the plug change.

prelude2perfect · 04-07-2012, 08:44 PM

Ummm, might want to recheck your installation, especially cylnider 1. Sounds to me like you didn't reinstall the coil correctly. Just go over everything you did and look at the spark plug DIY in the DIY section to make sure you did everything right.

osukf09 · 04-08-2012, 03:03 PM

Ya I didn't post it yesterday but I pulled cylinder 1 plug and it was all jacked up (loose, broken) for some reason. I didn't notice it upon install, but I went ahead and put my best shape 'old' plug in and everything was back to normal. So looks like I had a faulty plug and just need to buy a new one to put in there.

Even with only 5 new plugs, car is definitely running smoother (last plug change was about 23k ago) Although, I'm a little surprised that startups aren't as crisp and quick as they were after last plug install. Perhaps its the beginning of a hpfp issue, but we'll see.

jdub486 · 04-08-2012, 04:20 PM

Get the intake valve carbon build up cleaned. I had rough idle after new plugs and the carbon buildup removal was the only thing that ever helped. It really livened up the responsiveness of the engine at low and high rpms and smoothed the idle.

ArcticRik · 08-18-2012, 07:25 PM

Im having the same exactly problem as you are after i installed the new OEM plugs. Car runs fine until you stop at a light, rough idle and shakes with the AC off, with the AC on it seems to be ok but not a 100%. I decided to take the plugs out and put the old ones back in and it seemed to fix it a little bit, but still shakes slightly. Any ideas? I had the car scanned and no codes or anything shows up. I really want to put in new plugs but want to figure out whats going on before i do.

Gugs · 08-18-2012, 08:02 PM

^ you have a vacuum leak. Pretty straight forward.

ArcticRik · 08-19-2012, 05:58 PM

having a vacuum leak wouldnt throw a light?

04-07-2012, 03:47 PM	#1
osukf09 First Lieutenant 64 Rep 341 Posts Drives: 2011 e92 M3 ZCP Join Date: Nov 2010 Location: San Francisco, CA iTrader: (0)	Changed Spark Plugs, now rough/inconsistent idle...Help! Just changed my spark plugs with the Bosch replacement plugs. Did all 6 plugs, started the car up, and the rpm's are very inconsistent and its a very rough idle. Definitely the exact opposite of what I was expecting! Can anyone diagnose something that I may have done wrong here? Install was pretty straight forward, or so I thought... Note, I didn't put the engine cover back on or the cowl, filter, etc. as I wanted to start the car first. I've done JB4 install with no issue, and it's currently set on map 5. Should I try setting it to map 0 to see if the idle changes? I don't even want to drive the car with how bad the idle is right now... Any quick help is very much appreciated! Thanks guys
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04-07-2012, 04:04 PM	#2
Fred_Boosted Captain 90 Rep 632 Posts Drives: 335i Join Date: Nov 2011 Location: USA iTrader: (1) Garage List 2010 BMW 335i [8.00]	Yeah, set back to map 0 to see what happen. Are you sure you bought right plugs?
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04-07-2012, 04:10 PM	#3
osukf09 First Lieutenant 64 Rep 341 Posts Drives: 2011 e92 M3 ZCP Join Date: Nov 2010 Location: San Francisco, CA iTrader: (0)	Pretty sure, they've been mentioned in quite a few posts on here: Bosch OE plug, ZGR6STE2 I checked the old plugs and they had the same part # so I'm assuming they're correct. Just checked for codes and saw these new ones pop up: 2D2E- angle of throttle valve - intake pipe under pressure, correlation 29CD - Misfirings, Cylinder 1 I'm going to take out the plug for cylinder 1 and reinstall and see if that works. Both of these codes are brand new after the plug change.
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04-07-2012, 08:44 PM	#4
prelude2perfect Captain 60 Rep 621 Posts Drives: 2013 M5 and 2015 535i Join Date: Apr 2010 Location: Savannah, GA iTrader: (8)	Ummm, might want to recheck your installation, especially cylnider 1. Sounds to me like you didn't reinstall the coil correctly. Just go over everything you did and look at the spark plug DIY in the DIY section to make sure you did everything right.
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04-08-2012, 03:03 PM	#5
osukf09 First Lieutenant 64 Rep 341 Posts Drives: 2011 e92 M3 ZCP Join Date: Nov 2010 Location: San Francisco, CA iTrader: (0)	Ya I didn't post it yesterday but I pulled cylinder 1 plug and it was all jacked up (loose, broken) for some reason. I didn't notice it upon install, but I went ahead and put my best shape 'old' plug in and everything was back to normal. So looks like I had a faulty plug and just need to buy a new one to put in there. Even with only 5 new plugs, car is definitely running smoother (last plug change was about 23k ago) Although, I'm a little surprised that startups aren't as crisp and quick as they were after last plug install. Perhaps its the beginning of a hpfp issue, but we'll see.
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04-08-2012, 04:20 PM	#6
jdub486 Captain 273 Rep 749 Posts Drives: 19' M2C dct/ e90 335d dd Join Date: Sep 2011 Location: Maryland iTrader: (1)	Get the intake valve carbon build up cleaned. I had rough idle after new plugs and the carbon buildup removal was the only thing that ever helped. It really livened up the responsiveness of the engine at low and high rpms and smoothed the idle.
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08-18-2012, 07:25 PM	#7
ArcticRik Enthusiast 167 Rep 1,622 Posts Drives: Arctic Metallic E90 335i Join Date: Jan 2011 Location: Orlando iTrader: (11)	Im having the same exactly problem as you are after i installed the new OEM plugs. Car runs fine until you stop at a light, rough idle and shakes with the AC off, with the AC on it seems to be ok but not a 100%. I decided to take the plugs out and put the old ones back in and it seemed to fix it a little bit, but still shakes slightly. Any ideas? I had the car scanned and no codes or anything shows up. I really want to put in new plugs but want to figure out whats going on before i do.
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08-18-2012, 08:02 PM	#8
Gugs Banned 28 Rep 457 Posts Drives: E92 JetBlack Join Date: Jul 2012 Location: Long island iTrader: (1)	^ you have a vacuum leak. Pretty straight forward.
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08-19-2012, 05:58 PM	#9
ArcticRik Enthusiast 167 Rep 1,622 Posts Drives: Arctic Metallic E90 335i Join Date: Jan 2011 Location: Orlando iTrader: (11)	having a vacuum leak wouldnt throw a light?
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