2004 4.4 Rough Idle
 

Alright guys, I've read about an hour's worth on here trying to pin point a solution to my problem. I've read everything from it maybe bad gas to a bad CCV or MAF sensor. When i let my 2004 4.4i idle with the air conditioning OFF it settles into an idle around 500RPM. When I first start it up it is around 700RPMs and slows down to 500RPMs after about 15 seconds, which is where the rough idle takes place. When I turn my AC on it speeds up the engine to around 700RPMs and the rough idle disappears. This idle does not disappear once the engine warms up and occurs whenever I'm stopped with the AC turned off. Having it in Park or in Gear does not change anything either as it still idles rough when stopped. Once a little gas is applied to raise the RPMs the rough idle disappears. This seems to be a very common problem with the X5, but I can't find an exact solution. Any help is much appreciated.

Try disconnecting the MAF when the engine is running. It will hiccup, but then should return to idle. If that makes it better, then it's time for a new MAF.

The only other thing I can think of is vacuum lines. Your in Hotlanta, so the heat and humidty probably doesn't help in the summer time. Since this is happening now, i'd imagine that if you had a vacuum leak, it'd appear now since it's colder out. Does it go away at all after you've been driving it around for a while?

Well, I disconnected the MAF while the engine was running and it did the hiccup and returned to a rough idle still. I also cleaned the MAF sensor with MAF specific cleaner which did not do anything. After doing this my SES light came on for the first time as well. I have some other symptoms that may help solve the problem...

1. I have sudden jolts of power that jerks off the line from a stop sometimes, or while pressing the gas after coming to a rolling stop.

2. My power seems to not be up to par on consistant level... meaning sometimes I'll press the gas and it will respond immediately, and others it takes 2-3 seconds for it to respond and seems sluggish.

Once again, any help is greatly appreciated.

The only other quick things I can think of are vacuum links around the back of the engine where the oil seperator valve is. Some people have posted pics where the hoses just deteriorated and had cracks. Maybe you could try some old tricks like spraying carb cleaner or using a propane tanks and spraying it around all the rubber hoses and see if the idle changes at all. Try searching for the OSV threads so you can see the hoses I'm referring to.

this engine does not suffer from OSV like the older m62 and m54. although the diagphram does tear, but will set the MIL.

So after 30 seconds from cold start, the valve lift is transitioning from 6mm, to 0.3mm, this causes uneven cylinder filling which results in rough idleing. the correction is to replace the eccentric shafts and all 16 intermediate levers. to find out the correct levers to order, you must removed both valve covers and inspect the stamping. if you are out of warranty, you can ask bmw for assistance, in which they will cover the repair 100% parts depending on your relationship with them. although not recommended for x5's you can increase the lift from 0.3mm to 0.8mm through service function from BMW, this will improve the idleing characteristics.

Another one of those BMW won't tell you or replace it unless you ask the right questions. Nice.So no more blue smoke at startup symptoms, but then what about the threads I've only seen here where the lines clog? What's changed w/ the OSV valve then, because I'd rather not replace it if I don't have to when I hit 100k :).Also, why is it not recommended on X5's only to not change how far it opens?

all repairs made are per customer complaint only so i dont know what your angle is? the lines to the valve cover do get clogged by condensation from short distance driving in cold weather. but there is no fix for that. do you have a N62 engine? based on your signature, it looks like you dont. you'll have to replace yours every 60-80k. i cannot tell you why its not recommended, it says in the test plan not, it is "not allowed"

Just to be safe I check both Crankcase Vent valves "CCV" or "Oil Separator Valves" I believe they are sometimes called...one on each side, and both were free from holes or any defects. So, we can rule out those for now. I noticed my CCV hoses are made from hard plastic instead of rubber like some I've seen in pics on here. They are BMW hoses, is this an upgraded hose or should I replace them with rubber ones to be safe? Still trying to pinpoint my problem and will follow with updates when I have them.

So I got the P code today for my X5 and it is a P0112 which is an "Intake Air Termperature Circuit Low Input" This was the only code it threw, once again just updating as I find new information.

the intake air temp is inside the Air Mass Meter, the fault possibly set when you disconnected the sensor.