4.4i M62 Rough Idle - No Codes!
 

Hi All,

I have had a persistent rough idle for a long time now on my 2003 e53 4.4i M62 and can't figure out the cause. No Codes! At idle/low RPMs the engine is quite rough and the RPMs bounce when the RPMs drop (for instance when coming to a stop sign). If I drive the car hard for a long period of time the rough idle drastically improves until I turn the car off and let the engine go cold. In the mornings though the idle is really rough and on most normal trips the idle is rough the entire time. If I turn the AC on and raise the RPMs the rough idle is lessened. At higher RPMs the car runs beautifully. Here is what I have done so far.

- PCV valve and gasket on rear of intake.
- Oil separator and new hoses
- Intake gaskets on front of intake.
- Just did the valley pan and replaced intake gaskets underneath manifold
- O2 sensors replaced
- New MAF
- Valve Cover Gaskets

I have not smoked the engine after replacing the above and is the only thing I can think of next to do. Does anyone have any other suggestions? I keep hearing VANOS can cause rough idle as well which I have not addressed. Thoughts?

Sean

Have you done a compression reading on all the cylinders?

unplug your MAF, even though it's new, see if it smooths out after that.

also check your vac lines and in particular something called the main sucking jet. when i was working on my water pump / radiator hoses i knocked this bad bay around and it caused some trouble. i just put it all back to together and everything was fine. don't remember the codes, maybe i posted about it, but it definitely ran like crap without the peddle floored.

part #1
RealOEM.com BMW E53 X5 4.4i Vacuum control - engine

the top popped off it (whats pictured to the right, that comes apart). i lined it up properly, snapped it back into place, used a little glue/sealant and used a zip tie to hold it together.

What are you using to check codes ??

Also check your IVM (Integrated Supply Module). Something as simple as a bad/cold soldering inside the module has been known to cause fluctuating idle, as well as sluggish acceleration.
The module is very easy to get to. And if you are confident in using a soldering iron, you can fix it yourself in 30 mins.

Article about the DIY fix: IVM or why my engine runs sluggish??? N62 applies to ALL cars with it. E53/e65/e60/e63/e64/e66 | BMW LOGIC7

There can be lots of other causes for a bad idle. But it won't cost you anything to check this one.