6 reasons to avoid iridium spark plugs

[jaekormtb]

At my last plug change I decided to try Denso Iridium plugs instead of Bosch. Big mistake. The plugs in the photo have about 25,000 miles on them. All of the electrodes are cooked, a couple more than the rest. About 5k ago I had to replace one because it was so bad I got a misfire CEL. I just replaced with Bosch from Pelican....waaaaaaaay smoother!

[JFP in PA]

At my last plug change I decided to try Denso Iridium plugs instead of Bosch. Big mistake. The plugs in the photo have about 25,000 miles on them. All of the electrodes are cooked, a couple more than the rest. About 5k ago I had to replace one because it was so bad I got a misfire CEL. I just replaced with Bosch from Pelican....waaaaaaaay smoother!

 

Interesting particularly as we use Denso Iridium's all the time with no issues, particular in turbo cars, which tend to be hard on plugs.  From your photo, I only see two (center on left set, right plug on right set) that appear to have center electrode issues.

 

Anything unusual about the car, like an aftermarket re-flash?

[jaekormtb]

These are from my DD, a bone stock 99 C4. Lots of highway miles. It will be interesting to watch mpg, etc over the next few months.

Edited November 29, 2014 by jaekormtb

[Chicagospeed996]

Interesting. I put the NGK laser OEM replacement iridiums in. Seem ok to me so far. 5,000 miles. Hey have a disc of iridium instead of a needle point and four ground electrodes. Similar to OEM.

[JFP in PA]

These are from my DD, a bone stock 99 C4. Lots of highway miles. It will be interesting to watch mpg, etc over the next few months.

 

Do you remember which cylinders the really bad looking plugs came out of?

 

Like I said, we use them all the time in the shop with no real issues.

[jaekormtb]

The three on the left are driver's side, so the burned one is the center. The right are passenger side...I believe the burned plug is the rearmost plug.