Hey guys, I have a new problem that has me stumped. When warmed up I have varying degrees of uneven/rough idle. Most of the time the idle is as smooth as can be, every once and a while though it can get rough as if it doesn't have gas. Its never died on me, and I just give it a little gas. When cold it starts right up and idles great.

Plugs and wires are new (less than 5k) I pulled each plug and they looked fine, no oil or odd coloring, no "steam cleaning". Throttle body and plenum is clean as a whistle.

The IACV is also clean, but I don't think its working right. When I took it out it had a rattle to it and if I rotated the part I could see the block thing rotate on its on, it wasn't fixed in place. I did not touch it at all.

I guess my question is: is the metering block thing in the IACV supposed to move on its on?

 

Probably O2 sensor is lazy.
Or unstable.

You need to get a code scanner that can see live engine data
when it is running and check the O2's.

With a live scanner - you can look at all the live data and make sure it is
all reasonable.

If the O2's or the MAF
or temp sensors are unstable, then that will do it.

You may also have an air / vacuum leak that comes and goes.

put a 10mm socket on the intake plenum bolts and try to tighten them by only 5 degrees. See if any are loose.

 

That's what I thought originally, that the O2 sensors were acting up, but they are oscillating likely are supposed to. They are also pretty new (posted about them over the summer).
What should I expect as far as MAF readings? It should go up with engine speed right?

I'll go through and check the vaccum connections again.

What about my description of the IACV where the stepper motor is loose? Is that normal?

 

What do you mean the IAC is loose?
What octane gas are you burning and how many miles on the engine?

 

I always fill up with premium. Engine has 132k miles on it. It pulls strong, doesn't burn oil and there are no coolant leaks.

What I mean by the IACV being loose is when I had it out to clean (ended up being clean already) I noticed when I turned the part in my hand the block thing that controls the amount of air moved freely.

 

Please post a picture of "block thing loose".

 

I'm referring to the bit you can see in the middle of the IACV.

 

Don't go around prodding stuff, OBD is for a reason. Use a scanner, check the trims for lean/rich condition, check the temp sensors for stuff that makes sense. Check the oxygen sensor voltages while cold with the key on, you should have .455 or such. then start the car and check the voltages right away. If one sensor is like .855 and the rest are .455, you have heater voltage feeding into the sensor line. once the motor heats up (like 30 seconds) the ecu will trim that bank lean and the car will run like **** but not throw codes. Every disco that has come into my shop this week has had sketchy oxygen sensors and horrible gas mileage. All of them had cheese and water in the harness side plugs. one sensor plug looked fine and just fell apart when I touched it. Seriously I went through 8 front oxygen sensors this week.

 

Rovermastertech
When you post, I listen.
Fantastic advice.

 

So Hurricane Sandy business is picking up?