UPDATE - I tried the thread chaser to no avail. While the thread chaser felt like it was doing it's job, I couldn't get a new spark plug to grab the threads. Moved onto the thread insert method. However, I had to wait for the proper tool (Lisle 65200) which allowed for a longer reach. Boring out the old threads was straightforward (using bearing grease to capture much of the shavings). When I used compressed air to blow out the shavings (bottom dead center on the stroke), the rubber tip on the air nozzle shot off and into the piston chamber!!!!! After two hours of using a flexible claw grabber and a bore scope, I was able to grab the rubber tip and continue with the thread insert. I used a bit of Loctite 271 on the insert per instructions. Waited a few minutes and then seated the insert using the tamping tool. I checked the insert using the bore scope again and it looked good. Finished with a new plug and coil for all four cylinders - no codes or misfires. So, looks like it worked out. It wasn't too complicated and I didn't feel nervous or unsure about cutting the new threads. Easy peasy.



So, I have a 2002 Honda Civic Si that is my daily driver with 193K miles. Yesterday I got the check engine light then it started to flash. I drove back home immediately, less than one mile. In fact, the CEL stopped flashing. Pulled the code of P0301 misfire in No. 1 cylinder.

This morning pulled the coil on No 1 and it was fried. Fished out the rubber tip on the coil too. Majorly burned out and melted. To my surprise, the spark plug was quite loose. The plug was covered in soot but the spark thingee was intact (what's the tip called?) I got it out and found a few of the initial threads were buggered up. To my horror, I found that a fresh spark plug wouldn't catch the threads and just spins. My guess is that the female (non-man, excuse me ) threads in the head are either damaged, buggered up or missing all together. Of course, I have to snake down a 6" tube to get to the spark plug. Not easily accessible. So I have some thoughts on how to save this engine.

1) I'm going to borrow a bore scope to check for thread damage as well as check the piston chamber for damage to the piston head, piston walls or valves/seats.

2) The NGK is a M14x1.25 thread size. Should I try a thread chaser? Then vacuum out any debris that may fall into the piston chamber?

3) Try a thread repair kit where I tap new threads?

4) Go to the effort of pulling the head and have a machine shop fix the threads? This would involve a boat load of labor - but I've got time and a lift.

5) Install a JDM motor for $1200?

Thoughts on how to save this Honda engine?

This message has been edited. Last edited by: Russ59,

Blowing out spark plugs is a common problem on Ford 4.6L engines. I have lost two on my Crown Victoria. I bought a spark plug repair kit that is very easy to use. You ream out the hole, tap it to a larger size and then thread in a hardened seat. Make sure the valves are closed when reaming/tapping and blow out the chips with compressed air. It's about a 30. minute job. I would do some research and see if a similar repair kit is available for your engine.

JDM K20 [Z1?], or K20A with a 6MT swap, obviously
Or convert to RWD & go F20C, if we're dreaming.
EP3 is a fun little hatch, hope you're able to get it back on the road.

If the threads are junk in the head the answer is a repair kit, which are available for just about anything. Mostly easy to use but I've no experience on an Si to see what you have to do to get access.

How the hell does a spark plug 'blow out' of a cylinder head? Are the threads destroyed as a result of fretting corrosion, or by someone cross threading the spark plug? Shit materials/design?

Honestly I'd want to remove the head. It seems half-assed to do it any other way! If you're gonna tap, chase or re-tap the spark plug hole, how the hell would you keep all of the metal out of the cylinder otherwise? Serious question...

There are various spark plug hole thread repair schemes available. My concern is that all of them require making the original hole bigger. If any part of the steel thread insert protrudes into the combustion chamber, it will create a heat concentration/hot spot that may cause preignition. This will cause piston damage, and unlike spark knock (detonation), you won't necessarily hear it. There is no way of knowing if you have sufficient metal surrounding the plug so this doesn't happen without taking the head off. I saw this happen to an older Chrysler minivan engine, which has difficult access to the rear (firewall side) bank. There were chunks missing from the piston and the roof of the combustion chamber was pockmarked, all because a little "tail" of a previous Heli-coil protruded out of the head. If you have access to a trusted machine shop, you could ask them if they have worked with this engine and can advise you further.

I’m not familiar with Hondas but is the spark plug the same size thread? Maybe the wrong plug, a 10 or 12mm spark plug in the correct box? Especially when spark plugs are bought from a DIY type store (O’Reilly’s, AutoZone, Advance) it’s possible. As we used to in the business “pre tested”.

Possibly a bad male thread in the new spark plug? Might be worth the price of another spark plug or swap one out from a known good cylinder to see if it threads in. If so, I’d be hesitant to try the spark plug from cylinder #1 in a different cylinder, safer to buy another one then and toss it than taking the chance of boogering up another thread.

I've had to put inserts into many Honda 1.6, 1.8 and 2.0 heads.

I have the tool and inserts in my specialty tools toolbox.

It's easy to do.

If swapping in a JDM motor was anywhere on your radar before this little situation that is the route I would I go.

quote:

Originally posted by ScreamingCockatoo:
I've had to put inserts into many Honda 1.6, 1.8 and 2.0 heads.

I have the tool and inserts in my specialty tools toolbox.

It's easy to do.

Did you remove the cylinder head from the engine first? If not, how does one keep all of the metal from the drilling & tapping process out of the cylinder?

quote:

Originally posted by ScreamingCockatoo:
I've had to put inserts into many Honda 1.6, 1.8 and 2.0 heads.

I have the tool and inserts in my specialty tools toolbox.

It's easy to do.

This, if you area mechanically handy, HeliCoil makes spark plug repair kits, you can get one that fits your engines needs.

Call around to the Hi-Po JDM market shops in your area if you don't want to do it yourself, they can give you a lead on a shop that does it.

My 5.4 Ford blew out a plug, not uncommon, a plug doesn't get properly torqued and works loose, takes the threads with it when it comes out as well as the coil is usually destroyed.

I had a local shop do it as they had the kit and parts in stock, done in 1 day.

No need to spend $1200 on a new engine plus all the work, unless you "want" a new bigger displacement engine...

quote:

Originally posted by ScreamingCockatoo:
I've had to put inserts into many Honda 1.6, 1.8 and 2.0 heads.

I have the tool and inserts in my specialty tools toolbox.

It's easy to do.

Thanks for the input. I think I could do it based upon what you guys have shared plus some instructional videos.

I am going to call my local Honda independent shop tomorrow to get a quote for them re thread the heads. If it's just an hour's time, I'm inclined to have them do it. While I don't mind trying it myself, I don't have the luxury of screwing it up.

As for the JDM motor, that's kind of my plan when this motor does take fatal dump.

As for the mismatch of spark plugs, I don't think that's the case. I changed these plugs at 100K and it's ran for 93K miles since, so I don't believe that's the issue. I did pull the good plug from No 2 and tried to install in No 1 and that's when I realized the likely damage to the threads. I'm still hoping to bore scope this evening when I can borrow the camera.

quote:

Originally posted by nhracecraft:

quote:

Originally posted by ScreamingCockatoo:
I've had to put inserts into many Honda 1.6, 1.8 and 2.0 heads.

I have the tool and inserts in my specialty tools toolbox.

It's easy to do.

Did you remove the cylinder head from the engine first? If not, how does one keep all of the metal from the drilling & tapping process out of the cylinder?

No I do it with the head on the block, piston halfway TDC exhaust stroke, ream open the hole tap the hole then blow out the trash with the compressor hose.
Install the threaded insert per manufacturers instructions. Some have threadloc some do not.
The trash will shoot out of the exhaust valve otherwise.

Also if you load up the reamer and tap with grease, most of chips will stay on the grease.

.

Any chance I could just use a thread chaser first to see if that cleans it up sufficiently?

I got pics of the threads from a scope. Will figure out how to post them.

quote:

Originally posted by Russ59:
Any chance I could just use a thread chaser first to see if that cleans it up sufficiently?

I got pics of the threads from a scope. Will figure out how to post them.

*************************

That would be my first choice.


.

Anyone have a guess whether the head is cast iron or aluminum?

The independent shop was more confident with the repair if it was a cast iron head. I believe the valve cover is cast aluminum, just not sure about the head itself. The repair manual doesn't mention and I'm on the road for work and can't put my eyes on the car.

I would guess Aluminum. Reasons would be less weight and better heat dissipation.