ahc21ahc

I just changed the plugs on my 95 ES300 at 180K miles. I think these were the original plugs as they say "Denso Japan" whereas the new ones say "Denso Made in USA". In any case, the rear bank plugs are have a lot more carbon build up than the front plugs. I mean, they are noticably different. You can tell real quickly which are the front 3 plugs and which are the rear 3 plugs. Any ideas why this is? Thanks.

GrahamHill

Potentially an oxygen sensor if the car seems to run right. If it has any little issues it could be a vaccum leak on the front bank letting it run a little leaner and thus lighter looking plugs.

Pheonix

The last person that changed the plugs only changed half of them... So change all 6 & no harm, no foul.



It more common to find that on the older Lexus/Toyota v8's & easy to pick out b/c most left the factory with Denso plugs in one bank & NGK (Honda) in the other.

ahc21ahc

I'm not sure if only half were changed previously - the plugs look exactly the same and the wear on the threads is the same too. Just the tips have more black carbon build up. I do think the O2 sensor is original too, so it's due for a change.

GrahamHill

Mine had a bad O2 when I bought it @ 177K miles. Autozone can check your codes for free and dont let them tell you they "cant check no 95"

newr

I was thinking about the same thing since the 3 plugs on the back are a b!t(# to get to.

ahc21ahc

Could it be that the O2 sensor by the firewall isn't working too well? Anyone know how the two main O2 sensors work? Are they controlling each bank's fuel/air ratio independently? Thanks.

Pheonix

Well anything is possible, but I don't think the o2 sensor would change a new USD Denso plug to a tottally dirty JDM Denso plug by itself.


Change the plugs first, then decide on that.

GrahamHill

What plug is reccomended for the 3L?

AzNMpower

How do you get to the rear spark plugs? I remember we tried ourselves once, only to find the rear bank of cylinders impossible to get to........

92ES5sp

NGK or Denso thats it

92ES5sp

The upper intake plenum has to come off.
You might as well do valve covers while youre at it

Pheonix

Half the good maintenance is done with the intake manifold off. So it's best to just learn how to take it off. It's also much faster. Or you can use combinations of angle & flex shafts on a wratchet. Or get the special service tool from Toyota. Bawahahahahahahahaha! Ya right!

Valve cover gaskets (in your case the distributor gasket if needed). Distributor cap & rotor, PCV valve, spark plugs. All can be changed.
The intake manifolds, ISC, EGR & throttle body can all be cleaned out. The first will give more OEM like performance. More-so by alittlebit if you do alittle porting of atleast the ACIS flap.

And in the process you get to inspect alot of things. Vaccuum lines, hoses, spark plug gaskets, etc...

AdvanSC300

I highly recommend Denso with twin ground electrodes for the 1MZ-FE,if you use a cheap spark plug you will most likely get a misfire DTC in time..

I never remove upper intake plenum,useless you have coilpack on Bank 1(Note Bank 1 is the bank closet to the firewall)..