RichBinAZ

So a week before my son brings his 06 Xb over for an oil change at 55K, he is complaining of a vibration noise, in drive, at idle. I have a look under the hood and notice that the engine is moving around quite freely and has shaken the battery hold down straps loose.

Tightening those fixed that source of noise but the engine is still idling low enough to get into the 1st natural frequency vibration mode (bouncing all over the show).

Thinking it was a clogged Inlet Air Control (IAC) valve, we pulled the intake hose off and noticed the inlet to the throttle body was perfectly clean. No dirt, no oil, nothing. So we stopped that and took a look at the spark plugs.

Pulled out the plugs and noticed that the gap was really wide (.040"-.050") instead of the .028-.031 it should be. Upon closer inspection we could see that the center electrode was quite erroded away and even the outer ground was erroded. Those coils must put quite a spark down there.

Re-gapped the plugs and put them back in temporarily and that fixed the idle issue. The engine still shakes, but the revs don't dip low enough to get into the extreme mode.

At the oil change we did today, we replaced the plugs with Iridiums, figuring those should be errosion proof and he would never have to change those again. Idling vibes is now not a problem.

As a bonus, we checked the brake pads on the right side seeing we had that wheel off to do the oil change, and his original brakes are worn about 70%. 4mm left out of 11mm standard and the wear limit of 1mm. We will probably change those at either his 60 or 65K oil change. Probably change the fluid then also.

wolverines1012

I was having a similar issue with vibrations while in idle on my manual '06 xB around 50-55k miles, I had replaced the spark plugs with the NGK platinum plugs discussed here.

I figured it might just be telling me I needed to replace the plugs again but wasn't terribly excited about doing this every 30k miles. So I was researching and saw that I had never reset my ECU after replacing the plugs. So I followed the procedure found here, and the problem was solved... now I'm at 65k with no vibrations and no intention to replace the plugs just yet.

Just thought I'd share that with anyone having similar problems.

RichBinAZ

Thanks wolverine, I'll have the lad try it - if he can find the right fuse that is.
We just upped the idle speed, so if the reset works, we can drop the idle speed back to standard.

RichBinAZ

Pulling that fuse did help or do something and got it back into relearning mode. He says the idle speed went up a bit then came down after a few drives to a lower value than we set using the idle stop screw.

I asked him if he wants the idle stop returned to the stock setting and so far the answer is no. He likes the lack of vibration with the idle speed a bit higher.

I'm sure the engine mounts do as well.

jadeT

The sparks helped mine too

Reactor

That's a throttle stop screw- should never be used for idle adjustment.