SICAMG

Thought I would throw this out there before I dig in. For 4 years car has always had a very slight engine shake at cold start. Considered it to be just the way it is since it was very very slight.
Now it is worse and I noticed when under the hood yesterday you will hear a very faint, sparatic pop pop through the intake filter. It is very quiet, random and only during that cold start time for a 30-60 second time frame.
New plugs every year,new injectors 550cc, and wires.Fuel pressure 65psi as always at idle. Car has 69k on it.
I am thinking sticky lifter or valve issue but she runs perfect as always when problem is gone. Will do compression test and vacuum test tonight but thought I would ask ….maybe someone has come across it. Can't really see a valve being burnt on the intake side but who knows.
No codes by the way and all pids through STAR are good.

sjc246

Hmm. I have also noticed a "popping" noise from inside the intake (once the rpm slows down from the initial cold start). I don't have any abnormal vibrations or shaking (although it does perhaps decrease in rpm slightly each time it pops). Doesn't seem to be causing any problems as the car runs fine. I figured it was a result of my cams (SLR), but since you have it too, perhaps it's something else. You don't have SLR cams, by any change, do you? Did you find anything with the compression test?

SICAMG

No Cams and all test's are good. AND I can not duplicate the issue anymore. Very strange. The only thing I did was put 93 octane fuel in the tank instead of the normal 100 I use just for the hell of it since I needed fuel any way. Can't see that being an issue.

new55

this was posted by another member but may be useful

Bottom Line Up Front (BLUF): Engine misfires can occur frequently in the M156 engine due to failing coil(s) but may not trigger any diagnostic trouble codes (DTCs) or the "check engine" light to illuminate.

My E63 is sitting at 111k+ miles or so and I've already replaced one ignition coil based on information obtained from a DTC and check engine light warning by using the Torque mobile app. What I have noticed over the past two months or so is an apparent but very noticeable misfire developed again. I kept an eye over the symptoms as they gradually occured more frequently but wondered why I wasn't getting any DTCs. I decided to run the "Test Results" function of the Torque app and was able to pinpoint the offending coil by scrolling to the sections that break down misfire events for each cylinder. In my case, this time the coil was failing on cylinder #7 (see screenshot for reference). Note: The screenshot was taken after the car was driven a few times following the new coil install, hence the low numbers. I was sitting at like 35 misfires for the last 10 drive cycles and averaging around 5-7 for each current drive cycle. Either way, this shows how you can narrow down misfires for each individual cylinder, even if it isn't throwing any codes. I replaced the coil and all is well again. I am sure many M156s are either approaching or have surpassed the 100k mark when wear items always seem to start showing their ***. Just a helpful tidbit to keep in your mental toolbox. Cheapest place I was able to find coils was RockAuto at ~$28 not including shipping. The local parts stores are sometimes double this or more. It's good to have a spare lying around.

Strigoi

There's no need to run 100 octane unless you're running increased compression. All your doing is throwing away money (I'm guessing it costs more).

sjc246

I'm assuming he is tuned for it (ie. more timing than u can safely run with 93).

PieRat

SICAMG

100 Is for the tune I run. Timing 20-22* commanded and 16lbs of boost.

Strigoi

I read the part that I quoted as you run 100 just for the hell of it. Didn't realize you were tuned for that.

SICAMG

Yea...I find it cost more but the safety margin, especially with todays, gas is well worth it.
At the track I will run 108 octane but that's for the 1/2 mile run events.
This November the engine and trans comes out for a some updates and more boost so 100 fuel is really a must.

Davednconfused

I don't believe it's a misfire. My car does the same thing, and watching AFRs everything seems to be in check. No codes thrown ever.