Start Rough Idle
 

Hi Everyone, My 08 3.0 just have this problem.
When I start the car, the engine will shake alittle (you can feel it hard) for about 10 second and then it runs fine. Only happen when car is park over night or long period of time. Car has 58k. You think i need a tun-up like spark plugs and fuel filter change?
thanks

I would take it in ASAP and have it looked at. The 2008 has issues with fuel pumps, I went through two of them. This could be an early sign -- they can test for it.

If the fuel pump dies, you are toast. (Obviously there are many other potential issues but I doubt it's the plugs)

could be cam shaft sensor, I had similar problem on my 08

I have exactly the same problem and it's getting worse. Mine's '08 with about 4500 miles. The engine used to shake a little for like 10 seconds on fresh starts for a couple of years. Didn't do any more than that, so I let it be. But these days, it sometimes shakes like there's a storm outside and this one time the rev needle moved up and down like so crazy when started in the morning. It's in the dealer for service for over 10 days now.

Lmk the problem when you get the car back.. Dont have warranty anymore so i dont want to bring it in yet. I know they will charge me like crazy if i bring it in. I just change the air filter and its better now. doesnt do it everyday. just once and awhile. I think i need a tune-up or a vac leak somewhere.

Got a call from the service center saying it's something to do with wrong air/fuel mixture ratio and spark plugs. Don't know what they did but will find out tomorrow.

Whatever they did didn't fix the problem. It's going in again on Monday.

At 58k plugs are tired.... wouldn't hurt to replace...However, I don't think that will be the issue.

I'd look for vacuum leaks AND clean out any air control valves/fittings into the intake manifold- idle air control valve, etc,etc.

Autoque- MAF fouling can cause air/fuel issues. BMW dealers are morons when it comes to MAFs...they view them as "bad" or "good". Truth is they degrade.

All- Simply get some MAF cleaners and try it. IF IT IMPROVES, then replace the MAF. (Why? The maf cleaner removes the soluble contaminants- but not the oxidized stuff. If your maf improves with a cleaning of the soluble stuff there is undoubtedly oxidized crud on them- a replacement is warranted.) MAFs have a 50k service life, IMO

A

While there are many thing that can cause this, since it only shows symptoms at start-up a likely cause is the fuel pump/module, either taking too long to get up to pressure, or a leaky check valve that allows the system to depressurize too much while sitting.

The "only while sitting a long time" typically points to a bad check valve -- unfortunately the check valve is normally built-in as part of the fuel pump assembly and requires a fuel pump replacement.

Now, to put it in perspective, that has only been my experience with non-BMWs, but most fuel systems work on similar principles.

I can reproduce the symptom, actually a more violent one, in about 10~15 minutes.

What I do is first turn the ignition off and pull the key out. Wait for 10~15 minutes, during which time I do not do anything like opening the door or windows, I just stay put. While waiting, I can hear what sounds like HVAC deactivating and then about 10 minutes later I can hear another electric noise which I suppose is some module go sleeping mode.

About 5 minutes after that when I turn the ignition on without giving the system any time to wake up at all, the rpm needle goes crazy moving up and down around 500rpm and the engine vibrates violently causing the whole chassis to move about!