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Discussion Starter #1
Hey guys! Been quiet a while again since I posted last time, but I have another problem with my silver 2001 740il again haha. 148,000 miles. A few years ago this car would just start missing when sitting in traffic, but by the time I could get off the road to check what it was the car would run smooth again, and it would do this randomly and not very often. Last week this changed though because it missed immediately after starting up on the entire drivers bank. The car runs great out on the road and builds tons of power, just runs horrible at idle and low non cruising RPM. After checking the forum here first I decided to check the Cats (from a old post from around 2013) but to no avail, as non rattled when hit with a rubber hammer, and just to be sure I took the first o2 sensor out with non change in idle smoothness. Also changed coils from side to side, and put a new cam sensor in that I had laying around from a parts engine and put new plugs in without any change. I put fuel injector cleaner in it and filled with 93 and have ran about 50 miles and still idled rough. Also spark is great and strong on all cylinders. Also final test I did was compression, and it is roughly the same all the way around and is very strong. Any ideas? Thanks in advanced!


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Discussion Starter #3
Would a manifold leave cause a dead miss on all 4 cylinders? I have done the test with ether now. The code I have is random misfire with fuel cutoff.


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Ether? OMG! lol.

So random misfire on 5 through 8, compression good, only at idle and slow cruising speed. Hmm. Any history of top end maintenance as this has been, according
to your post, happening for years? Verified as bank 2 via INPA or otherwise? Cleared codes and re-verified?

The only common denominator I can think of is the intake camshaft. Possible oil starvation due to oil rail clog, causing wear to the cam lobes/lifters. that would cause an idle misfire,
but would still perform ok under power load. No noise would be evident. Wouldn't show up in a compression test, either.
Pull the valve cover, check the lobes for rounding over.

I could be way off, seen wilder stuff over the years. If the cam/cam timing is good then you have a hunt for errant dme/ignition/injection issues to deal with.
 

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Discussion Starter #5
I put timing guides in the car about a year and a half ago and 20k ago. Was in perfect condition then, and it was doing this (randomly though) before then, and the issue just popped up about 100 miles ago (continuously) and the day I posted the original post. If I have a chance this weekend I'll pull it and check though. The code dosent say bank two but pulling the coils say yes haha. I can pull and leave all coils on driver bank unplugged with no change in idle.


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That's a strange one. Wouldn't suspect ignition or fuel if it runs well off idle.
If the cam looks good check your cam timing. Lock the pin with the cam numbers up and make sure
the intake cam hasn't slipped.

I would expect to see bank 2 timing codes in that scenario though.
Keep us posted.
 
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