How to resolve an uneven idle?
 

Hello everyone I have been visiting this site for various reasons for about a year now and finally decided to sign up. I have a 2004 4.4 X5 that I am completely in love with. One thing that has me slightly concerned is that it idles unevenly, I would not say a rough idle but you can just see the tachometer vary slightly only while running at rest (and of course you can hear it). Also at night the interior lights oscilate slightly in intensity while idling. As soon as you give it a little bit a gas it purrs perfectly. I have done a little research and think it may be either the Idle Control Valve or the O2 sensor. Any help would be appreciated because (like all of us) I hate replacing a $150 part only to have solved nothing. Also I am new so if this is posted in the wrong section just let me know! Thanks again

I used to have that problem.

Dealership changed the fuel pump, the fuel filter, the spark plugs and it is much better but not 100%.

check smooth running values. anything above -+2.5 is bad, but anything above -+1 is still considered rough. you can also try setting the valvetronic to min lift, and disconnecting the vvt motors and see if they are still running rough.

How many miles are on the car, what sort of mpg are you getting at speed, and why do you suspect 02s? I believe it is less likely to be 02s than ICV, but if you do not have any SES codes currently, it may just as well be the turn up stuff that mth posted...specifically A) not enough gas, B)not enough air or C)not enough spark. These would probably manifest themselves at other times too though, not just idle and you would probably notice a decrease in miles per gallon or power, or both.

With the idle situation, you need to see if you can pry apart if it is running poorly only at idle, or at all conditions, as the ICV directly controls intake air only for idle, and could be the problem if everything else is operating within tolerances. The other thing I can think of showing up at idle only is a vacuum leak of some kind, or a malfunctioning vacuum booster or something of that nature.

If it were my car, I would check the plugs, check the intake for oil, keep track of the mileage it is getting and under what conditions, and see if I couldn't narrow this down.

Thanks for your responses guys, I think I will follow Lo Jacks recommendation and start with the plugs, since even if it doesn't fix it, it's probably time for new plugs anyway. I'll let you know the outcome.

Did this even get fixed - the uneven idle?
I have a 2006 4.4i and been experiencing the uneven idle.

I've replaced my spark plugs and been using premium gas also. My lights don't dim though unevenly. just can feel and hear it.

please help!!!!

same problem, same engine. my lights dont dim, but it does give me a "pulsating" idle--only when i'm at rest in drive

funny.. i have noticed the same with my 2006 4.4i. when i am stopped at a light with foot on the brake - i feel a vibration... as if the idling is set too high.. i never noticed this before and was thinking it may be because the temp drop outside? I was never ever able to feel the engine thru the steering wheel.. it was always a silent idle.. Now I can feel it quite easily.

I am just shy of 60K, and need to do the InspectionII.... so maybe its time to change plugs etc.....

Check your motor and tranny mounts.

So... Its been a long time... I am back from Afghanistan, and the answer I came up with is sort of embarrassing. It turns out the uneven idle goes away in the summer but seems to come back in the winter, could it be the cold? Actually it sort of was the cold, since the idle is only uneven when I have the heated seats on. I can only relate that to some sensor noticing a large draw on the vehicles electrical systems and maybe it compensates by running the motor at a slightly higher RPM, totally speculative, but that's what I came up with, of course after replacing spark plugs and an O2 sensor.