All:

I've had this happen twice in the past 18 months, and I was wondering if any of you have seen the same thing.

I'm running Denso Iridium IT-22's in a fairly conservative setup (maybe 400 RWHP, 15-16 PSI max boost). At least "conservative" by the typical standards these days where an 11-second truck doesn't even warrant a mention. I've had plugs suddenly go belly-up and stop firing (permanently) twice in the past 18 months. The first time took me a couple months to isolate and diagnose, the second (today) took about 10 minutes.

Both failures were immediately after a hard WOT blast through the gears (to maybe 110 MPH or so). I should note that I do this a lot and make a lot of passes at the track, so it's not like every time I pound on it a plug goes out.

The dead plugs look visually pristine (which didn't help with the original diagnosis). I've examined both under a low-power bonocular microscope and nothing looks odd. They just won't fire.

The failures were in different positions. The first was driver's front, the second was passenger's second from front.

The failure pattern was the same each time. Intermittent misfiring under heavy boost/rpm, quickly worsening to a dead cylinder from idle to WOT.

Any ideas? Should I be using a colder heat range (IT-24) at this level of boost?

Curious if anyone has had this sort of random failure pattern with Densos.

 

I would s h ! tcan the Denso's..IMO they are a waste of money, my truck ran like crap on them.. Get a set of NGKTR6's

 

That's the weird thing. I run GREAT with them, except when one of them suddenly and unexpectedly quits firing for no apparent reason. I like the performance, I'm not pleased at all with the reliability.

Obviusly reason enough to look elsewhere, unless I'm doing something wrong (like the incorrect heat range).

 

I run the same plugs as you IT22's I gapped them at .032. I haven't had any problems. Below are my mods. I don't think these plugs are crap and I've been running these plugs for years and never had any problems and I run my truck in the winter.

 

I've been running them for years, and I've not heard of the issue you are mentioning. 24's would be too cold for your boost level.

Steve

 

What are you gapping them at?

 

You could put in about 4 sets of the NGK TR-6s for the price of a set of Densos.And in 5 years of running then I have never had one go bad!!! Jim

 

I think all of us know how much denso's and ngk's cost. I think he has issues other than plugs.

 

Gapped at 0.038", per tuner and forum recommendations. Too loose?

 

What mods do you have?

 

Basic bolt-ons, 15-16 PSI boost.

 

I'd try closing them to .034. Your not maxing out your MAF?

 

+1

Detonation.

 

close your gap to .032

 

What sometimes happens to Denso's (and usually it happen to me at the end of the run after I let off the pedal) is an extremely fine hair line crack develops that under normal conditions you would never see, (not even if your looking). It appears to be perfect (especially since the fine crack is usually inside below what you can see) BUT then you turn it upside down and beat the ever living chit out of it, and all of a sudden the plug is in 2 pieces.

Most would miss it and it doesnt seperate easy sometimes. I went through at least 12 sets so believe me I know. Now anytime I change plugs it's common practice for me to turn the plug upside down and beat it half to death....

Example
Look good and hard, see anything wrong with that plug ???










after turning it upside down and beating it silly
Waa Laa



Although they are amazing plugs for whatever reason some L's love them, and others dont .....