01 740i rough start and misfire - BMW Forum - BimmerWerkz.com
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#1 (permalink) Old 07-13-2013, 11:45 AM
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01 740i rough start and misfire

i have recently purchased a 01 740i sport car runs great fast ..its sweet!!
a couple of weeks ago in the am 1s start of the day it ran rough i taped the throttle a couple of times and it smoothed out and ran fine the rest of the day so in the am every 1st start i would just tap the gas a couple of times and no problem no check light nothing the other day i noticed once i got off of work it did it again now its when the car sits for a few hours i.e. over night or at work while sitting for 4 to 8 hours
i when home and put my scanner on the car and found multiple misfires and misfire on cyl 3n so i swapped the coil pac 3to 4 cleared the code and took it for a spin i jumped on it trying to get it to fail on it hard several times came back checked the code and again multiple misfires and misfire on cyl 3 i am not sure where to go next could the plug to the coil pac be bad?
if so can it be swapped wit another for testing purposes?
Please help
Thanks in advance
riverDan
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#2 (permalink) Old 07-15-2013, 10:01 AM
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I would swap the plug for sure. If you just got the car and dont know when the plugs were last changed, I would replace them all now. This way youll have a better idea of what parts are new and which will be nearing the end of their life.


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#3 (permalink) Old 07-15-2013, 10:17 AM
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Thanks Lord Vader
I had that same idea myself i pulled the plug and noticed it was a single ground autolite plugs...?
so i went down to the local auto parts and ordered the stock NGK dual ground plugs
do you think the extra ground would make the difference??
I also started it up in the am and used break cleaner trying to find a leak ether their is no leak or i did not do it correctly
any ideas are greatly appreciated
Thanks
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#4 (permalink) Old 07-16-2013, 08:38 AM
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Try disconnecting the MAF and see if that helps. I had performance issues with mine when it was cold, no power until it warmed up, and it turned out to be a faulty MAF. By disconnecting the faulty MAF the Engine Management system went into a default state where the performance was better than before, but not as good as after I changed the MAF, then it really shone.


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#5 (permalink) Old 07-16-2013, 09:20 AM
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Quote:
Originally Posted by riverDan View Post
Thanks Lord Vader
I had that same idea myself i pulled the plug and noticed it was a single ground autolite plugs...?
so i went down to the local auto parts and ordered the stock NGK dual ground plugs
do you think the extra ground would make the difference??
I also started it up in the am and used break cleaner trying to find a leak ether their is no leak or i did not do it correctly
any ideas are greatly appreciated
Thanks
riverDan
I use single prong NKG plugs in my E36 and it runs fine. It might decrease my fuel economy a little, but not enough I would ever notice. The reason I only run the single or dual prong as opposed to the OEM four prong plugs is because a spark can only make the jump at ONE point. The other four prongs help it find a spark, but the extra prongs dont make the spark any better.

You need to use Carb cleaner. It will cause a surge in idle if their is a leak and the carb cleaner gets into the system. Brake cleaner is just to remove grease and grime and it evaporates too fast.


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#6 (permalink) Old 07-16-2013, 10:41 AM
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Brettski,
i changed the MAF when i purchased the car someone had damaged the MAF and tried their had at JB weld i thought that was cheesy so i poney'd up for a new Bosh MAF but i will try that tonight

Lord Vader,
I thought i saw on a youtube Vid that the Guy used break cleaner thought it sounded weird but i had it so that what i used i will pick up a can and try that tonight as well any known areas i should pay special attention to?
Thanks
Guys your input is much appreciated
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