2007 BMW 328i N51 E90 - Constant Misfiring only at idle.

[Reacher]

Heyo! Been helping my friend for the past 2 weeks straight bring his E90 sedan back from the dead.

When initially starting the car, cold or warm, it of course idles a bit high ~1100rpm for its warmup procedure, then smothly lowers down over the course of 60 seconds and idles perfectly at ~650rpm for another 30 seconds. THEN... lol. Let the misfires begin. I'm logging misfires in cylinders 1,4,5, and 6. If I give the car even a little gas, to raise the RPM's up to 1000, it runs perfectly smooth with no misfires. Other than feeling the misfires when sitting at red lights, the car accelerates and holds speed perfectly. Engine revs strong, and winds down to idle gracefully.

Is there anything I should do or check before just throwing parts at it and buying 6 new coil packs? Money is very tight.
Could it be the N51 fuel pump? Or would I be getting lean codes along with the misfires?

If we shut down the car, and wait 5 mins, then start it back up, it will idle smooth for another minute before the misfires creep in. As of this moment we have no other fault codes other than misfire codes.

Fresh Spark Plugs all gapped to ~0.43. NGK ILZFR6D11
Di-Electric Grease Applied to the boots of the coils. They are bosch coils of unknown age. Connectors are fully seated.
Fresh Air Filter. Oil Filter. Oil. and Coolant. all Done.
Cleaned Vanos Solenoids, they looked gunk free already.


EDIT:
Replacing Coils Resolved Issue! OE Delphi seems far better than the Bosch Ones.

[Reacher]

Oops, forgot to add, rotating the coils from Cylinders 2 and 3, with cylinders 4 and 6, resulted in cylinders 4 and 6 to continue misfiring, but also caused cylinder 3 start misfiring. Fun times. Perhaps weve got multiple issues. Ordering a set of OE Delphi Coils Now. However any other checks to perform while I wait for the coils to arrive in the mail would be very appreciated.

[drewusmaximus]

Replace the spark plugs with OEM plugs. My stepson had the same problem with his car on cylinder 2 and it turned out to be the spark plug. It fouled out. Replace the plugs and report back. Good luck.

[Reacher]

All plugs are fresh, is there something wrong with what i'm running? FCP Euro lists them as OEM. All gapped to ~0.43. NGK ILZFR6D11

[gusm325]

What do you mean "bringing it back from the dead"?
Has it been sitting for a long time?
Have you fresh gasoline in it?

[Reacher]

> damn im gonna type it out now lol.
Car hadn't ran in 2 years. Previous Owner was neglectful. Back Right door seal was missing, ~15 gallons of water sitting in it.
No Electrical Power, even with a new battery.

Stripped the Interior, soaked the carpet in cleaner and white vinegar, got it dry. Replaced battery again.
Found out the entire fuse box had been essentially scrambled like a Rubik's cube. Manually went over every. single. fuse. confirming amperage and fuse condition.
Cleaned up some of the rusty grounds coming off the main body harness. Gave the Car a hug. Electrical Power Came Back Baby!

Reinstalled Interior. Installed new door seal.

Got it running... or perhaps walkin-... crawling... yeah crawling.

Siphoned the tank, it had old 87 in it. Put in 5 gallons of fresh 93 from shell. (Fixed Lean Codes)
Replaced Fuel Pump Gasket and Clamp (Fixed EVAP Code.)
Changed Oil and Filter. Flushed Coolant. Found out Electric Coolant Pump was not working and covered in rtv sillicone. Replaced.
Engine was Failing to idle when winding down, and was hesitating when revved moderately.
Did Spark Plugs. Engine Now winds down to idle and rev's strong.

Legitimately all is good except the misfires at idle, which we never noticed until now because we weren't running the engine long enough for them to present themselves.

[drewusmaximus]

According to realoem.com, NGK LZFR6AP11GS is the plug we should use in our cars. The Delphi model 12138616153 is what we should use. I'm sure the plugs you have won't make much of a difference, to the point you experience misfires. It sound slike the coils are shot. Although expensive, it's a good idea to replace them all for piece of mind. Keep us updated.

[gusm325]

Moving the coils around did not make much difference.
Well I guess you are in Florida with high humidity-unplug the MAF and see if the idle stabilizes...
If that makes no difference- check that no critters have nested in the intake, (now a days they have those air flaps electrically operated; can't remember if the 07 had one or two and they must open and close properly...), since it only misfires at idle perhaps it's time for 2 cans of Techron and a good old fashion Italian tune up.
The Bimmer needs to run and breathe.

[Reacher]

Apologies to Revive the Thread, however I wanted to report back that replacing the coils resolved all the misfires at idle. Good to know that even when an engine revs without misfiring, misfires at idle can still be coils. Learned something new!

[drewusmaximus]

Apologies to Revive the Thread, however I wanted to report back that replacing the coils resolved all the misfires at idle. Good to know that even when an engine revs without misfiring, misfires at idle can still be coils. Learned something new!

That's good news!! I just replaced ignition coil #6 because i had a slight rough idle and I had the P306 code. I bought the car used and everything seems original, which I assume the coils are original, since they are Delphi and have the light gray body. So, Since the car has 108k, I decided to be proactive and replace the common parts that go bad at 100k. I strongly suggest replacing the coolant flange with aluminum, $12.00 amazon. I'm sure the flange on your car is rotted and the last thing you want to do is be driving when that flange goes. It's a quick 20 minutes job. Put a towel under the flange to catch the little bit of coolant you'll lose. The trick to getting the stuck flange out of the hose is to squeeze it with a vice grip so that the flange collapses inside the hose and pulls right out. You'll need a new hose clamp. Get some coolant and replace what you lost. Bleed the system and you're done! Glad it worked out!!