How long do the denso plugs usually last?

[Dave Compson]

Does anyone know how long the denso plugs are supposte to last? I have about 17k on mine and am getting a little cold start stumble. The stumble feels like fouled plugs. It comes and goes, and it just started a couple of days ago. I think its time to buy another set. I havent pulled them yet, just thought i'd ask the group. And this is in dennis' forum because i got them from him, and i feel he knows best.

Thanks everyone..

Oh, and thanks dennis for taking care of us.

[2003 MIB]

Does anyone know how long the denso plugs are supposte to last? I have about 17k on mine and am getting a little cold start stumble. The stumble feels like fouled plugs. It comes and goes, and it just started a couple of days ago. I think its time to buy another set. I havent pulled them yet, just thought i'd ask the group. And this is in dennis' forum because i got them from him, and i feel he knows best.

Thanks everyone..

Oh, and thanks dennis for taking care of us.
I had the cold start stumble at about 4,000 miles on the denso plugs. I thought it was from sitting- I don't use the MM every day. I found some empty highway and did some 120+mph runs and it went away and has never returned. I don't know why it worked but it did. Might be worth a shot.

[Dave Compson]

In a couple of hours, i am driving from vegas to san diego. I am sure that will help clean things out a bit. Thanks for the reply.

[MERCMAN]

Gee, just hate to hear that you HAVE to run it that fast :lol: Just what we all need another excuse

[CRUZTAKER]

Pull them and check them. Mine were in bad shape after 12k. One had no electrode left. I posted pics in the gallery back in the day.

[gonzo50]

Pull them and check them. Mine were in bad shape after 12k. One had no electrode left. I posted pics in the gallery back in the day.
I thought that these Denso Plugs were top of the line stuff, why all the shortcomings and short life status ? :confused:

[SergntMac]

Dennis once said 60K or better, and I've got about 20K on my IT-22ss, no problems to report. But, my MM gets regular exercise in the upper RPMs too. I would think that any carbon build up from low use would kill the Densos.

[CRUZTAKER]

Dennis once said 60K or better....
That's funny! I'm trying to find the thread from last winter regarding the IT-20's, it was either in the thread or a phone call, but I was told otherwise....WAAAAAY otherwise.:confused:

[Smokie]

Direct from the horse's mouth:

Q. How long will Iridium Last?
A. Iridium use represents the most significant technological advance in automotive spark plug manufacturing, since platinum was introduced in the early eighties. As vehicle manufacturers produce increasingly complex and efficient automobiles, there is a greater need for long-life plugs that can tolerate leaner fuel mixtures and improved combustion processes. DENSO has responded to this need by developing its Iridium alloy (http://www.densoiridium.com/powertechnology.htm), originally for OE applications. For example, many newer Lexus’ and Toyota models carry an ultra long-life Iridium plug variation (.7mm with platinum tipped ground) that is capable of up to 120,000 miles of service. DENSO Iridium Power plugs, with their .4mm center electrode (http://www.densoiridium.com/spconstruction.htm), have been developed for performance applications. Because gradual wear will “round-off” firing points over time, the concentrated firing power and voltage requirement (http://www.densoiridium.com/voltagerequirements.htm) benefits will be reduced. For this reason, DENSO advises replacement after 30,000 miles.

[SergntMac]

OOOps...Well then, guess I had better order a new set...Thanks!

[BUCKWHEAT]

I just pulled mine & replaced them after 10000 miles. They looked great, with no variation in color or obvious wear. I numbered the old ones & will check gap by cylinder just to see. Conclusion, they're fine & i'll put them back in after I put 20k on this set.

[schuvwj]

My Denso's only lasted about 9,000 miles when the electrodes began to break off on two of the eight plugs so I repalced them with Motocraft AWSFA-12C at about 1/4 the cost of the Denso's.
The AWSFA-12C plugs are two ranges colder than 4.6L stock plugs and I drove her everyday this winter with no problems.
I've had the Motocraft AWSFA-12C in now for about 14,000 miles. I need to pull a couple and see how they are doing.

[Dennis Reinhart]

Does anyone know how long the denso plugs are supposte to last? I have about 17k on mine and am getting a little cold start stumble. The stumble feels like fouled plugs. It comes and goes, and it just started a couple of days ago. I think its time to buy another set. I havent pulled them yet, just thought i'd ask the group. And this is in dennis' forum because i got them from him, and i feel he knows best.

Thanks everyone..

Oh, and thanks dennis for taking care of us.

The plugs should last 60k they have a warranty if you have problems I will replace them for FREE

[Marauderjack]

'NUF SAID!!!!! :banana:

[schuvwj]

Nuf said!!!

What was said?

[Marauderjack]

What was said just before I said.....'NUF SAID????? :confused:

Read "Dr. Reinhart's" statement.......I think that should sum it up??

Does for me anyway!!! :burnout:

Marauderjack :D

[Murader03]

Nuf said!!!

What was said?
Read the post from Dennis!

[Dave Compson]

Thanks dennis, ill pull them and let you know either way.

Thank you

[schuvwj]

Read the post from Dennis!

Mauader03 I read Dennis's statement about the 60,000 mile Denso warranty.
I bought 8 new Denso's from Dennis last year and logged 9,000 miles on them when several electrods broke off.

Then why did I have to BUY my Denso replacement plugs from Dennis?
Warranty? Where!

This is why I will always use Motorcraft plugs.

[HotrodMerc]

Bill, that sounds very disappointing, not to mention potentially damaging to your engine. Did you have any piston or valve damage, or worse, cyl. wall? And, did you notice any performance gain with the plugs, not that it would be easy to notice a difference in plugs along with other mods. Have a new '04, havn't driven it yet, but have talked with Rheinhart about mods, and have contacted others, such as Diablo, and Chris Johnson. No answers yet. Would appreciate your feedback. Joe

[schuvwj]

Bill, that sounds very disappointing, not to mention potentially damaging to your engine. Did you have any piston or valve damage, or worse, cyl. wall? And, did you notice any performance gain with the plugs, not that it would be easy to notice a difference in plugs along with other mods. Have a new '04, havn't driven it yet, but have talked with Rheinhart about mods, and have contacted others, such as Diablo, and Chris Johnson. No answers yet. Would appreciate your feedback. Joe

Joe my luck with Denso plugs has been very disappointing from a longevity standpoint. I’ve had 2 of the 8 Denso electrodes break without warning in 9,000 miles. Don’t know if this caused any engine damage. I hope not!

There has been information posted on this website that Denso’s can give your MM a 2HP to 4HP gain but in my opinion weight the costs vs. the gains and Motorcraft plugs is still the best overall option.

My 2 cents.

[Smokie]

How did your engine run ? A broken electrode would create a huge gap for the spark to bridge, I assume you pulled the plugs because the engine was not running properly ?

[schuvwj]

How did your engine run ? A broken electrode would create a huge gap for the spark to bridge, I assume you pulled the plugs because the engine was not running properly ?

Yes when the Denso plug in number 8 cylinder broke it idled very rough.

[junehhan]

I think i've been persuaded by this thread to use Motorcraft plugs, only Motorcraft plugs, and nothing but Motorcraft plugs.........