Guys - Many wonder about what spark plugs are recommended for our 1UZFE's, when to change them, how to tell if they are bad, etc. Last weekend my Father-in-Law and I changed our plugs. Hopefully this thread will help some of you. Note - I went from Denso platinum to Denso iridium (plus wires). He simply replaced his Denso Iridium with the same.

Mike made notes - here they are: I removed 8 NGK iridium spark plugs, four are shown. These plugs have been in the car since new and have 120,000 miles on them. Used spark plug condition is a great indicator of cylinder condition and combustion efficiency. The tan coating on the center porcelain shows a perfect burn in a good condition cylinder. ( I have always used Mobil 1 oil, a high quality oil filter and K&N air filter which helps keep the plugs in a good environment.) Note the new plug in the center is close to old plugs in cleanliness, etc. All used plugs had a 0.040" gap. The new Denso iridium plugs were factory gaped at 0.042" After 120,000 miles on these plugs I thought it was time to change them. After seeing their condition I am sure I could go another 50,000 miles. Since I have changed, cleaned and regapped spark plugs for 40 years (my cars,) I was very impressed with the life and condition of these slugs. In past years I was doing good to get 15-20k miles on a set. Also the Lexus manual specifies either NGK or Denso iridium spark plugs. I am sure anyone would be happy with either brand properly applied. I do notice improved responsiveness with the new plugs.

Note these 14mm plugs are torqued at 20lbs with clean threads and no lube on the threads per the manufacture specifications.


Pic one:

 

Pic 2 (Note new plug in middle for comparison):

Amazing how clean the plugs were after 120,000 miles - shows how clean the motor was running. Enjoy

 

They really are clean , i can't tell if the flash is whiting out the burn or if it is slightly too lean. Still it is very complete combustion.

Notice those brown rings on the threads , that is where the plugs are grounding efficiently so it darkens more from heat. A perfect ground will have a very even brown tone which is rare.

 

Thanks for the GREAT PIC; Have not seen any LS plugs until now. Eye opener.

 

That's how mine look too. I changed mine at 60K and I felt they could easily go another 40K+. Since I went through the joys of clearing all the hardware I just put the fresh ones in.

 

I just switched over to iridium plugs from platinum plugs I put 102,000 on the platinum and they looked the same as your iridium nice and brown to a gray color and clean. I got the iridium plugs from a friend who sold his car and he gave them to me today I got 25mpg on my 91 lexus using the new iridium plugs and I also use mobil one extended and the K&N air filter I also put the mobil one transmission fluid in the trans and power steering and rear end I don't know if it helps getter better mileage. I have 203,000 miles on the speedo and I even have the orginal hoses air condition pump and radiator I was told by an radiator expert to use the toyota red anti freeze and distilled water and I have for more than 9 years and so far no problems with the car. I did the same thing on a 1986 cressida and got 429,000 miles on everything and it is still on the road I am going to push the iridium plugs to about 100,000 miles plus.

 

Wow that is good to hear - the longevity is amazing on your Cresida. I should be good until 300,000+ miles with these iridium. My platinum Denso's were slightly worse (in condition) than my Father-in-Law's but for over 210,000 miles they were exceptionally clean.

 

great timing. i bought spark plugs yesturday. but i got the ngk standards, those okay?

what about spark plug wires? what do you guys recommend?

 

Stock wires work fine or you could go with some aftermarket NGKs.

 

NGK platinum is actually what came installed maybe in pre 98 vehicles. When I changed mine on my 95 the first time they were NGK. Also, my Father-in-Law took out his and they were Denso iridium from the factory!

Regarding the wires I installed Denso first time fit and they were a no brainer - fit exactly like OEM.

 

Dandy job on the plug photos! It is nice to know what they look like after 100,000 miles from a well maintained LS 400.

I hear, from this forum I think, that it is a hellish job to remove and replace a couple of them (at least awkward, for sure). What is your feeling about it?

 

Sorry for the late post. Changing them really was not hard at all. You must be careful removing the air box assemble as there are tow vacuum lines. I broke one but repaired it easily. Changing the plugs on the engine was not hard and took an hour or so. You need a torque wrench to set at 18 PSI and a long extension to get the plugs out. As long as tools are available it is quite easy.

When I had my timing belt changed they wanted $180 or so to replace plugs.

 

hey steve, you can set your tq wrench at PSI?

i think you mean lb-ft

 

What? You haven't heard of the Snap-On Mark III platinum edition torque wrench? It has PSI and hp ratings

 

Ha ha LOL you got me on that one - lb-ft is definitely what I meant - had a long week D Also filled up after one full week on the new plugs and tank average was 25.7 MPG. It is slightly higher than what I normally average.