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Rough idle/check engine light flashing

14K views 15 replies 7 participants last post by  Xlr8tin 
#1 ·
Hello, i need some help figuring out why my 98 740i is idiling rough. It gives me a code for a mis fire on cylinder #1. It also seems to spit and sputter at times when i press the gas pedal. Not sure what's going on but my bimmer sounds like a small truck now. HELP!!!!!
 
#2 ·
i guess it could be many things from the ignition coil being faulty, fouled spark plug, bad injector or in some cases engine mechanical damage like a broken valve spring for that cylinder. i would swap coils around and see if the coil that comes off cylinder 1 travels to the cylinder that you installed it into. mark them so you dont forget. those coils fail frequently. cylinder 1 is the closest to the coolant reservour tank.
 
#3 ·
Mis Fire on Cylinder 1/Rough Idle

Hello, i need some help figuring out why my 98 740i is idiling rough. It gives me a code for a mis fire on cylinder #1. It also seems to spit and sputter at times when i press the gas pedal. Not sure what's going on but my bimmer sounds like a small truck now. HELP!!!!!
 
#4 · (Edited)
Valve cover gaskets are prone to leak as they get hard and brittle from underhood heat. First step is to, like cntlaper1 said, pull the plugs. Usually, if the VC gaskets are leaking, if you shine a light down the plug hole before taking the plug out, you will see oil. You will also see oil on the tip of the coilpack (where it meets with the plug) if the leak is bad enough. This will cause a misfire and foul the plugs in question.

Hope this helps!
 
#5 ·
Check ignition coils

Just received word that two ignition coils on my 2001 740i are bad and need replacement. Issue was car would rough idle in park as well as at stop lights....so much so that I was bouncing in my seat. Otherwise it was driving great when not idling. It appears the fault codes indicate coils 2 and 3 need replacement.
Hope this helps.
 
#6 ·
OP's last post (of 3 total) was nearly 5 years ago. By now this has either been fixed or the car was sold.

Welcome to the 'fest!
 
#9 ·
Thankfully this post hasn't disappeared. My car has been starting to do that as of the last couple of weeks. Idles rough as a cob when at a stop light and holding the break, and has some major hesitation when pushing the throttle from a dead stop. I have a new set of plugs for it, might try swapping those out this weekend and see if there's any oil in the plug holes like GLHExorcist mentioned.
 
#7 ·
Thank you!

Thank you for the welcome message.
I have a 2001 740i as original owner. I am trying to keep it until 2021 and for last 3 years have been having issues. Have used this forum for advice and now just getting to contribute. Car has always been dealership repaired so I figured I could repay advice by posting my issues with dealership solutions so others wouldn't have to pay the $$$$$$$ I am paying!
 
#8 ·
Orignial owner...OUCH! That depreciation has to hurt. About a month ago I was looking on craigslist and it appears as though the average price for a 740i/iL in my area is down to about $2000 (probably why there has been a recent boost in new owners here). Maybe by 2021 it will go back up due to rarity and in range to become a classic/antique. I got mine last year for $2600 (at least 4th owner).

So please feel free to post all your knowledge, there are about 15 of us active in here that could learn a few things from someone who's driven the car that long. But if the thread is more than a couple years old and the OP has a post count under 20 it might be worth it just to start a new thread.

And then there are threads like what's you odometer reading and what's your look like that can be resurrected anytime. (Hint: show us some pics)
 
#10 ·
Check ignition coils too

I had all plugs replaced as had not been done for 14 years. Car had 41,000 miles on it as I am original owner. Two weeks after new plugs, car started rough idle so took it back in and it was two coils gone bad. When changing plugs, don't forget to replace the boots too
 
#13 ·
How about the pacman port under the hood?
 
#14 ·
That one I am unaware of..... Got a picture? I know my old 325E had an OBD I plug in under the hood but it was right out in the open....
 
#15 ·
Hmm, I wonder if this is another yearly change...

In mine it is a 20 pin round connector attached to the passenger wheel well. When you unscrew the cap you'll see 20 pins and in the center is a little post shaped like pac-man.

Use google for images of "bmw e38 under hood pacman dlc".
 
#16 ·
Having one from brand new or something that has had it from new is the best way to go. Getting them used for 2K is a nightmare as they have too many issues when not upkept. Mine has been a nightmare, but I love driving itm and they look amazing
 
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