Small shake/vibration at idle

[4x4mike]

I've noticed in the past two weeks something different at idle. About a year and a half ago I cleaned the IAC valve because it was idling low (~450 rpm) and dying. Every since then I've paid attention to the RPM's to make sure everything is fine. My normal idle for more than a year has been between 700 and 750 RPM after everything is warm and the AC is off. Now the normal idle is around 600 and 650 with a slight rumble at idle. I notice it at stop lights. With both feet on the floor I can feel it.

I've looked under the hood for any loose components to see if they are vibrating and found nothing loose. Even if something was loose it doesn't explain the lowered RPM. Ken said it might be the spark plugs. I assume they are stock from the factory and the wires say 1999 on them (my MY).

Any other ideas about what it might be without opening the whole vibration thread of past? I was thinking it was the gas but I've been going through it like it's going out of style (I've put about 6,000 miles on it the past 5 months). Fuel filter?

[Seanz0rz]

pull your intake hose off, look where the PCV valve hose comes in and see if there is a bunch of oil. if there is, the valve failed and started letting oil into the intake, clogging the IAC which lies at the bottom of the TB. then its the same as before.

personally i would replace the spark plugs and wires anyway. before you do, go ahead and run a good seafoam treatment through the engine so you wont foul up the new plugs. spark plugs from the dealer are a bargain. wires are around 60 dollars (FOR 3 WIRES!!!) and i think are best purchased from the internet. just get good quality ones from a brand you recognize. replacing plugs and wires solved my stumbling problem i had a couple years back.

[4x4mike]

Didn't think about the PCV. Are you saying take the intake hose off the TB? Or from the air box? I have cleaned the IAC before and everything looked good. Maybe I'll have to give it a second look.

I've always been leary about Seafoam. I guess I'll have to do a little online research to see how to do it on the 4runner. I remember reading about how to do it on my old truck and didn't like the idea of stalling out the engine with the stuff. I'd also have to find somewhere to do it as I wish to not piss off my neighbors.

Because I'm not in a huge hurry and have some other stuff going on I was going to shop around which included talking with Rafa.

Is your stumbling problem documented here on UY? I don't remember it for some reason.

[Crinale]

seafoam usage in our trucks is documented in the UY wiki...
http://www.ultimateyota.com/index.php?option=com_openwiki&Itemid=60&id=seafoam_usage

[4x4mike]

seafoam usage in our trucks is documented in the UY wiki...
http://www.ultimateyota.com/index.php?option=com_openwiki&Itemid=60&id=seafoam_usage


Well I'll be. First time to the wiki, might have to try this.

[Seanz0rz]

i posted up about it. i believe it was summer of 07 that the problem was occurring.

found the thread: http://www.ultimateyota.com/index.php?option=com_smf&Itemid=26&topic=1960.0

new fuel filter did not solve the issue, but plugs/wires did. the plugs looked ok, wires were pretty old though, no splits that i found however.

i guess i never posted up my solution in that thread. you obviously have a different issue causing yours to run rough at idle, and thats why i would look at the IACV again. problem with pcv valves, they fail (6k part that never gets replaced at 6k, more like 60k) and the intake starts sucking oil from the engine into the intake. on vehicles that have the IAC at 12, 3, or 9 o'clock positions, this isnt as big of a problem(although it will still draw in particulate matter and clog) but on our TB the IACV is at the 6 o'clock position, allowing the oil an easy path to clog it up. generous use of some TB cleaner will help clean it out.

i think a good list of general maintence will solve this problem. here is what i would do:
replace fuel filter (34 dollars IIRC)
replace plugs and wires (80 or so from the stealer, buy plugs from them and wires elsewhere)
replace PCV valve (any autoparts store, 5-10 dollars)
clean intake, MAF, TB, and IACV with correct cleaners
check for obstructed vac lines, esp in the PCV valve line. mine looked like the artery of a 500 pound, 50 year old man!

also, im assuming no CEL codes, which is incredibly frustrating.

[4x4mike]

Thanks Sean.
Yeah, no CEL lights. I didn't get lights with my IACV and dying either.

[Scuba]

Is the PCV really a 6k part?

[CJM]

Yea a pcv valve is no more than maybe 10 bucks.