RPM not super steady?

[superacerc]

Here's a question I'll put to the forum. The XK has never really idled very steadily. Most of the time its not bad but sometimes hunts around a little bit. Anyone else ever have this issue? It doesn't cause any problems and it's not drastic by any means but the lights will dim a little cause it'll idle really low and waiver around. It almost seems like it's too low in general.
Ideas?

P.S. I feel almost guilty for the amount of time i've been looking at the Subaru forum for my forester. I'm not used to having so many options on everything!! I can read for hours.

[Aggie07]

I have the 4.7l as well and have always had a very steady idle. In fact, when I first bought it there were times sitting at a stop light that I could barely tell the engine was running.

I only notice the slight fluctuation in RPMs when the AC compressor kicks on and off. Have you tried cleaning the IAC valve to see if that has any affect?

[strokeZ]

Every once in a while it wandered a bit - but rarely happens after I installed the Jet Stage 1 Chip.

[superacerc]

It does it with the air off or on. It's definitely not from the A/C. It's just a random fluctuation. Almost feels like it wants to shut off on very rare occasions. It's always done this (or at least since i've been in houston).

[Matt]

2007 4.7L uses an IAC right? Might want to try cleaning the valve to see if that smoothes it out (or just replace it depending how many miles you have)

[criket]

Long shot but maybe it could be the oil pump? Do you have an oil pressure gauge on your dash? Reason I say oil pump is this past weekend, I was driving my brother in law's chevy truck and at the stop lights, the oil pressure would drop and it would almost stutter out. I put it in Nuetral and rev the motor a bit and it was fine. It didnt' do it constantly but it happened a few times.

[Matt]

Loss of oil pressure is due to a loss of RPM, not the other way around. Mechanical pumps depend on engine RPM to pick up the oil.... so if the engine starts to stall for some reason you will lose oil pressure.

[Aggie07]

I only notice the slight fluctuation in RPMs when the AC compressor kicks on and off. Have you tried cleaning the IAC valve to see if that has any affect?

Sorry, I was not implying that your A/C could be the issue. I was simply stating that is about the only time my RPMs fluctuate, which is normal.

My suggestion was to clean your IAC valve, or like Matt said, get a new one if you have high mileage already.

[cico7]

I had a little trouble following war wagon's line there, but (did I say that) I got it now....rough idle, trying to pull through ....Take a look at the spark plug threads, they addressed rough idle. A wider gap or worn plug can add to the idle issue.
I have had problems in the past, but not since I replaced my plugs.

[The_War_Wagon]

Got new plugs three weeks ago - .040 gap. First time I've ever had that issue, and the Jeep wasn't completely cold (I'd driven about a mile & half in heavy stop 'n' go traffic to that point), and it was VERY damp & rainy yesterday. I'm running 89 octane with a Superchips 87 tune, so theres most of the mitigating factors I can think of, for reference.