When do iridium spark plugs go bad?

[jtvang125]

I don't think the plugs were ever changed (106k miles) yet so I decided to do it this past weekend. Lexus recommends that I use iridium plugs so that's what I used. When I removed the old plugs the sharp end of the iridium tip was completely gone leaving a dull cone shaped stub.

After I was done I started the car up and immediately noticed a slight shake from the motor but stopped after about 30 seconds. I'm assuming the ecu had to readjust to the changes or because I had to remove the airmass sensor. Well anyways the car certainly feels stronger and the throttle feels more responsive. Gas mileage did seem to improve as well but I didn't take an formal readings (~250 mile trip I take often. Previous gas gauge shows level 1/4 left. After change level shows just a tad below halfway mark.)

 

[Apex]

I think they recommend 60k miles on those. Different iridium plugs have different recommendations on lifespan though. Some (ie. Denso 0.4mm iridiums) have a 30k mile lifespan.

 

[T2urtle]

that shaking was from misfire, ECU doesn't adjust for anything. It reads it instantly.

iridum plugs are 60-100k depends on who tells u what. platinums are 60k.


I honestly cant see myself putting in 10$/ plug and not worrying about it for 60k. Spark plugs are windows for how your car is running internally. My maxima was suggested to run plat at 60k, but i use my copper plugs for 20-30k and they are just 2$ a peice. plugs are not hard to replace

you mentioned your lexus and dealership suggested so i hope you didn't get any bosch crap +4 or +2, and went with denso, NGK which are OEM from the lexus.