lexixel

Hi,

I'm planning on replacing the spark plugs this weekend. At the same time, I hope to check the vacuum hoses. Does anyone have the vacuum diagram for this engine?

I'm sensing some intermittent not-so-smoothness at Idle in P or N (cold and hot). The plugs are from 2009 (45k miles though), so I'm changing them and checking their conditions first.

Other suspects are (1) MAF and (2) injectors.

Thanks

lexixel

I found this one in case anybody wants to get it:

http://www.ebay.com/itm/LEXUS-LS430-...kAAOSwEzxYZ9bz

No wonder I didn't see many hoses - it's very simple.

lexixel

Had nothing to do this afternoon and changed the spark plugs:

Really stupid move. The old ones look just like the new ones (with some gunk in the exposed threads, but the lead looks new and the gap is the same as the new ones).

Moreover, it is (to me) extremely difficult as a spark plug job. Took me 3 hours: The battery box needs to be removed, and the power steering fluid reservoir needs to be lifted. There is no clearance for a torque wrench without a CV bit - really not sure about the torque with it (I targeted 21 Nm).

Still drives the same.

Also checked the vacuum lines and cleaned the MAF sensor. The idle thing must be from carbon build-up, I guess.

Harold57

Also check your motor mounts. A number of folks have reported that bad motor mounts have caused the engine to seem to idle roughly.

lexixel

Have to take that back.

Did an Italian tune up today, 4th gear 120-140 kph (circa 3300) for 30 min and 3th for 5 min (circa 4200). Fuel consumption is down 10-15% during this compared to normal driving in D. Probably it's mostly the MAF cleaning. Idle is better.

I don't think it's the mounts, because then it would get worse in gear. In my case, it's only noticeable in P/N. It's not really rough idle, just not as smooth as expected. Next time I start it cold we'll know if the Italian tune up helped.

Bgw70

is it possible you have a vacuum leak?
that would cause a rough idle

lexixel

Yes, it's possible, but I can't find any. The engine is not running lean, and the idle is stable, so it's not likely.

I think the idle is better now but can still be smoother (don't know if it's possible).

texsexlex

iTrader: (3)

....hey lexixel, not saying that it is or isn't the mounts, but you'll feel the vibration more when the car is in park,neutral or idling in gear with your foot on the brake....so I wouldn't totally eliminate the motor mounts