I'd have to look to know for sure, but my expectation would be that just the last thread or so would be damaged where the plug might have rattled a bit before actually being forced out. If you're lucky perhaps only the "lip" of the thread (where the beginging of the threading is at the top of the spark plug hole in the head) is damaged and that's what is keeping the plug from now re-engaging the threads.

The fix is the tricky part. See if you can get a good look at the threading for that plug. If just a portion of the first thread is damaged you might be able to actually use the plug to catch the undamaged thread and have the plug itself clean up the damaged area as it screws in. Or you could get a tap and use it to recut the threading into the undamaged section. The risk in either of these is cross threading and cutting/"repairing" the damaged thread and having that not match the undamaged part.

If it were me I'd get a tap, which is tapered, insert it into the hole deep enough to begin engaging the undamaged threading (you'd have to hold it at a slight angle after you inserted it partly to catch the tap in the undamaged plug hole threading) and gently twist the tap deeper using the undamaged thread as the guide until the tap cut/repaired the upper damaged section.

It's not for the faint of heart and it wouldn't be easy due to the recess of the plug home; taking off the valve cover might help a lot.

Or you could pull the cylinder head and repair it with a tap from below. Or take it to a dealer and let them do it.

Sorry for your troubles, and I hope some of this helps.

 

Just remember to vacuum out your cylinder after you do your tapping!

I tourque the plugs up to 22 ft-lbs as you have to use a long extension. Just don't tourque up to 40 because then you may have to do some machine work.

Jeremy

 

Any time I inspect spark plugs I dust them off and re-gap them.

I have no stored codes now. Yippee!

Jeremy

 

I can certainly understand the concerns folks are having regarding the spark plugs.....keep in mind that the original plugs were designed for the application are intended to be a long term consumable (i.e 100k miles).

Regarding any recommendation I would make, is to use an ignition lab scope to determine the condition of the plugs and the entire combustion process, this is a non intrusive test and provides concrete data upon which to make a decision!
When the voltages go out side of the specification, inefficiencies start to creep in.
I do not recommend the use of any additives on the plug threads, nor do I recommend the casual and unnecessary removal of the plugs and wires.
The heads are aluminum and the threads certainly will not withstand too many cycles of plug replacement. Using anti seize compounds on the threads can insulate the proper grounding of the plugs and induce a weak spark......likewise damaged threads do not provide a proper ground (on a waste spark system the spark energy travel through the head then over to the companion plug). The proper way to repair the damaged threads is to use the repair kit designated for that purposes and install a heli coil.
To summarize: let the lab scope data dictate when to replace, always torque to proper specs. IMHO.

 

Anybody know if there's an affordable hand held oscilloscope that we could use to check our ignition system over?

Jeremy

 

Most anti seize compounds are very conductive, containing aluminum
and or copper in them. I think you risk more thread deterioration over time by
not using one on the plug threads.

 

A number of automotive applications are out there and range in price from about $1500 and up. Some of these scopes are laptop based. Some vendors are OTC, Snap-On, MAC, Fluke, Pico Scope, ATS. Interro PDA, and a number of others. I think the dealer as well as some local repair shops have these tools and hopefully may charge a minimum fee to hook up and provide a hardcopy print out; one at idle and a snap throttle.

 

Has anyone tried using the "Back Tap"?
http://www.back-tap.com/


Jim
(who always uses a dab of anti-sieze and torques to 22 ft/lbs, and never has had any spark plug issues)

 

So is the difference between a:
BKR7EQUP (OEM JCW)
and
BKR7EIX (iridium)

a matter of chocolate vs. vanilla, or do the iridiums have an advantage over the OEM multiprong?

 

I had found this article and the comments on MF useful

 

For me the thread on MF was a bit confusing. I've decided after my Denso plug incident to go back to stock. The MF thread makes mention that if you have the SC reduction pulley (which I have), then you "should" use a plug that's colder to prevent detonation.

So, does stock plug + 15% pulley = bad ?

 

I saw the MF article, and my only takeaway was that you can use either, and the JCW replacement interval depends on what the meaning of 'service interval' is.

Blue Brummie, I don't think the stock plugs are 'bad' with a 15%, but from my understanding, the colder plug will be 'better' as it helps reduce detonation.

My suspicion is that 'iridium' is simply a marketing follow-on to platinum.
I'll probably go with the multiprong, as I loathe marketing.
The only real advantage I see with the multiprong is the reduced electrode wear due to the reverse firing cylinders.
I haven't seen any particulars on the iridium other than it's the latest greatest thing.

 

I've looked at those suppliers before(expensive but durable/reliable).

Is there no handheld scope in the $200-$500 range?

Could these oscilloscopes work for automotive ignition voltage outputs?

http://www.mbelectronics.com/view.aspx?id=328

Jeremy

 

You don't need anything more than stock plugs/coilpack/wires, with stock gap. Its not a 400WHP car, dont spend more than $5 per plug. Also make them hand tight and then another 1/4 - 1/8 turn. No need to torque them, even though its 22 ft/lbs, we dont wan't to strip a cylendar head.

 

Real quick lesson on "cold plugs vs hot plugs"
Cold plugs have a longer electrode, which absorbs more heat energy than a "hot plug" which adversely absorbs less heat energy. Back in the stone age (1970's), Cold plugs would be fitted on a car that saw long distance drives, and warm plugs were used on your grandmothers car that saw short 3 minute trips to the grocery store. With todays technology, that sort of spark plug servicing is not as important to the ignition system operation as it used to be. Cold plugs vs stock is a marketing scheme in the same way as changing your oil every 3,000 miles. Bottom line is its not my decision, but its good to know what a cold plug is before investing $ over stock.

 

What about the Bosch Fusion four-prong plugs?

 

Where do you find OEM plugs for $5??

 

+1

 

I agree

 

Not that I am aware of. There are some inductive probes with LEDs that indicate firing voltage levels when touched to a firing wire, these are more crude and I have never used one.

 

So these handheld scopes-with the inductive probes(only up to 600V)-couldn't handle automotive ignitions? Too bad because it would have been a neat little option to check variation in spark from cylinder to cylinder and variation over the life of each type of plug.

Jeremy

 

Autozone. That was an exaggerated figure, I think I bought Bosch plugs last winter at about $6 per plug.

They're not the NGK plugs that come factory, but they are of equal quality.

 

I found an OBD scan tool / scope that has an option to add a secondary ignition pickup that will display the secondary KV. the scan tool cost $500 and the secondary option cost another $100 dollars. Do a search for CJ4 by injectoclean

 

Jereme,

I have the APS230 scope, and while it works, it was difficult to use for the ignition because the signal jumps aaround quite a bit. I beleive this is due to the unit being a general purpose scope. On the scopes designed for automotive you will get a more stable display because the unit actually takes several readings then displays an average of the signal, this way the signal looks more stable and can be read compared to a unit that lacks the ability to average and displays a live signal. this is why for example the MODIS and other such devices produce such a stable signal. hope this helps.

 

Ok thanks for your guidance Frenchie.

Jeremy