Dip in RPM in park / neutral, louder than normal hum when stopped in Drive.
 

Well, almost made it 1.5 months without new concerns on our 2003 disco.

It finally decided to get 'real' cold (8-20) here in Chicago, and we also just got our first snow.

Coincidentally, or not, within the last week our truck has started to have a louder than normal low hum / vibration when you come to a stop and are still in drive with brake applied. The hum does not really begin until you come to a complete stop, and it is not always to the same degree / severity. When it is most noticeable, there is a pulsing nature to it, rather than a consistent vibration.

Shifting the truck into Neutral or Park sees the RPMs constantly dipping and raising from ~600-750. To me, the pulse that I hear when in Drive matches the fluctuations of the RPMs moving up and down. When in Neutral and it is doing the dipping of RPM, there is a slight shudder to the truck, not unlike the shuttering the truck had when my MAF connection came loose (or was not hooked up correctly) after my power steering pump replacement.

I've been searching through the forum, this thread seemed to be the same problem, but not too many replies:https://landroverforums.com/forum/ge...e-issue-16950/


I tried to take video with my iphone of the tach while in drive and neutral while stopped, as well as video of the engine compartment while the problem is occuring:

http://vimeo.com/81606339
http://vimeo.com/81606340

Strangely, we have remote start, so I'll use that in the morning and let the truck run for 2-5 minutes before driving. I have not observed the problem once when getting into the truck from a cold start, I have only seen it occur once driven and coming to a stop.

Any ideas where to start are greatly appreciated. Maf starting to fail? Throttle Body Needle Cleaning? Idle Air Controller? As always, thanks!

Another thing I just realized I should have mentioned:

I'm 95% sure this problem was not observed until Monday (12/9) morning. I put roughly 3/4's of a tank of Gas in on Saturday(12/7) morning (it was just over 1/4 left in the tank). It was driven ~5-10 miles on Saturday and I don't believe I drove at all on Sunday. Could this have been brought on by bad gas? I always buy premium, though I suspect the previous owner was not as discerning. The gas purchased on 12/7 was at a station I have filled at several times before as it's right by my house.

Praying to the based god for it to just be bad gas, I put a bottle of Seafom into the truck last night, we'll see what happens next.

It does sound like idle air control valve with "the searching for proper rpm" sound.
if the seafoam does nothing (well besides smoke out the neighborhood) I'd lean towards the iac as the culprit.