Spark plug ejected - need advice on repair

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J

jbpace

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My '96 FZJ80 goes into limp-home mode driving to my mom's house (i.e. the middle of nowhere) just before midnight last night. While I made it to her house, something was very clearly wrong.

This morning I examine it and find the #5 spark plug has been blown out of the head (note the stripped threads) and embedded in the cover plate. The entire #5 connector plug is missing from the plug wire.

So, how do I repair it enough for a 3 hour drive home? I know I need new plugs and a new plug wire set. Don't know if the threads are stripped in the head or not. What else should I worry about?

At least I'm stranded at my mom's until my wife can pick me up ;).

Thanks,
Jon
photo.webp
 
Well thats the craziest thing i ever saw. Could be the plug loosened and the pressure pushed it thru. But the threads look okay on the plug. Dunno what the head looks like but hopefully a spark plug thread chaser may work if the threads aren't too bad on the head. Good luck, sorry about that!
 
It looks like the plug was only partly threaded in the head (1/4) way and popped out. First go to an auto parts store and get a plug thread chaser. Retread the plug hole and than reinstall new plug. While your at it check your other plugs to make sure there seated as well.
JM2C
 
Yes, it looks like it was only threaded partway in or came loose. I believe the head is aluminum, so what you see at the end of the plug may be aluminum from the head. A thread chaser may do the trick. Use some grease on it to keep the cuttings from falling into the cylinder.

Good luck!
 
Trapper50cal said:
and it sounds like you'll need a plug wire as well...

Hopefully there is enough thread left to hold a plug safely. If not, you'll have to tap it to a larger plug size and always have one plug that is different than the rest.
Click to expand...

I wonder if a helicoil would work....then you could keep the same size.
 
Some auto parts stores sell kits for fixing this problem. This is a somewhat common issue with older BMW's if the plugs aren't properly torqued. I see 2-3 BMW'S a year where customers tried to do their own plugs but didn't torture them and end up with this problem.
 
get a mirror and a flashlight or whatever it takes to see the threads in the cylinder head, such that you can. To verfiy that the threads are not damaged or see if you can tell the extent of the damage. Do not drive or run the engine unless you can securley install the plug and whatever wires or whatever else is damaged that is critical to the engine running.

I would be wondering who installed the last set of spark plugs.

they make a thread chaser for damage spark plug threads....you might try and find one that would work properly for that engine.

plug was either loose or was not threaded properly on install.

you might start to think about having the truck towed home...unlikely you will be able to fix it properly for 3hrour drive.
 
Spark Plug Repair Procedure and btdt

I see a couple of these a year in the 4 valve Audi turbo engines. One towed to me after a dealer screwed up the spark plug install. The time-sert repair is a better repair for spark plugs than the helicoils. IME, the helicoils tend to come out with spark plug removal. The usual cause for backing out is incorrect spark plug install procedure. The FSM does not list a spark plug torque, but the accepted spec for a 14mm thread and gasketed spark plug into an aluminum head is recommended to be 22lb/ft (which is also what Audi FSM lists for their aluminum head engines using the same plug application)

The procedure I use is to torque all plugs to 22lb/ft, then go back one at a time, loosen and retorque to 22lb/ft. This tends to properly set the gasket crush that must be done on new plugs.

To repair in situ, you should start with a thread chaser/repair tap. If you can not get to 22lb/ft torque, then a time-sert repair is necessary. Tough to do in situ, but not impossible. The biggest issue is making sure the drill is exactly vertical to the head plane, or you risk a botched repair. For number 5, I would remove the hood, so you have a lot of room to work. You will also need an extra long drill bit to get down into the spark plug hole with the valve cover on. For the deep centered spark plugs in the Audis, I ended up ordering a custom long drill bit and had it milled down from 1/2 to 3/8. I use grease on the drill bit and tap, and clean them often. Take your time, take all day if you have to... Screwing it up means the head comes off, and a few more days of work you shouldn't have to do.

This failure is more common than folks think. Even using the procedure above, I routinely re-torque turbo spark plugs at 6 month intervals. Here, I'd venture to guess that #5 didn't get tightened down, or the gasket didn't get set properly on install.

BTW, many race engine builders put Time-serts in all aluminum head engines, as it's a stronger fastener connection than the original steel into aluminum

HTH, IMO, IME

Scott J
94 FZJ80 Supercharged
6 x NGK BKR6EIX 22lb/ft
 
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I would try just rethreading a new plug in and see how it goes. If it can torque to 22ft/lbs, then drive it home like that. It looks like it only stripped the top few threads. If it strips then do the time sert. JMHO but thats what I would try. If you screw it up your down a few days anyway so might as well see if you can just put a plug in it then drive it home where a friend can help you out.
 
bmwjnky said:
Some auto parts stores sell kits for fixing this problem. This is a somewhat common issue with older BMW's if the plugs aren't properly torqued. I see 2-3 BMW'S a year where customers tried to do their own plugs but didn't torture them and end up with this problem.
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Do you recommend the water-boarding the plugs? Or just start with pulling their nails?
 
gtfour43 said:
I would try just rethreading a new plug in and see how it goes. If it can torque to 22ft/lbs, then drive it home like that. It looks like it only stripped the top few threads. If it strips then do the time sert. JMHO but thats what I would try. If you screw it up your down a few days anyway so might as well see if you can just put a plug in it then drive it home where a friend can help you out.
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X 3-5 Like I said before its not that bad.
I looks like only a few threads. Just rethread the hole. If your over worried rent a inspection scope from a tool rental place. You'll find only a few threads messed up like the plug. 1/4 at the most. No need to go over board here. Retread it and be done with it. Use oil as you clean them up.
If you drill it you open up a bigger can of worms than you need. Drill shavings, lots in the head, must be perfect the first time in not so perfect conditions.
It's just not at this point yet. The most that's bad is shown on the plug, very little.
 
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Facts I should have originally posted:

  • Engine has 227k miles on it
  • TRD supercharger installed at 101k miles
  • Plugs are Denso Iridium (IK22 - 2 steps colder than stock)
  • Plugs were torqued to 18 ft-lbf (Denso guideline)
  • Plugs have 98k miles on them (rated for 30k, but wrote 120k interval in my maintenance book :censor:)

SUMOTOY said:
This failure is more common than folks think. Even using the procedure above, I routinely re-torque turbo spark plugs at 6 month intervals. Here, I'd venture to guess that #5 didn't get tightened down, or the gasket didn't get set properly on install.
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Scott nailed it - I hadn't re-checked torque since installation. The bottom third of the plug threads are stripped - the rest are perfect - and a quick search shows numerous reports of plugs working loose over time. I bet they really work loose after triple service time. :bang:

Time to order new plugs & wiring harness, and ensure everything stays torqued to 22 ft-lbf.

:confused: Question - if I use a thread chaser in-situ, aren't shavings going to fall into the cylinders? Is liberally greasing the tool enough to trap everything?

Thanks for the objective insights,
Jon
 
No matter which one you do you'll have some shavings. By rethreading you'll have very few compared to drilling it out larger. You could vac out some maybe but some will fall in. No way around it unless you pull the head.
You'll never catch it all but less is best.
 
jbpace said:
Facts I should have originally posted:

  • Engine has 227k miles on it
  • TRD supercharger installed at 101k miles
  • Plugs are Denso Iridium (IK22 - 2 steps colder than stock)
  • Plugs were torqued to 18 ft-lbf (Denso guideline)
  • Plugs have 98k miles on them (rated for 30k, but wrote 120k interval in my maintenance book :censor:)



Scott nailed it - I hadn't re-checked torque since installation. The bottom third of the plug threads are stripped - the rest are perfect - and a quick search shows numerous reports of plugs working loose over time. I bet they really work loose after triple service time. :bang:

Time to order new plugs & wiring harness, and ensure everything stays torqued to 22 ft-lbf.

:confused: Question - if I use a thread chaser in-situ, aren't shavings going to fall into the cylinders? Is liberally greasing the tool enough to trap everything?

Thanks for the objective insights,
Jon
Click to expand...

If you coat the thread-chaser with grease, white grease is what I used, you will catch most of the shavings, the rest will follow the way of the exhaust. If you are worried about the shavings hurting anything, make sure that piston is at TDC, then attach a small hose to a vacuum cleaner and pick up the rest. From the picture it looks like you stripped the top 3rd of the threads so the bottom threads should be ok. Good luck.
 
+1 what Gustina said but I wouldn't move the piston to TDC. You just chance trapping the shaving inbetween the piston and first ring land that way.

I've done 30-45 repairs on various vehicles that have spit them out(BMWs, Mazdas,Audis).

The shavings shouldn't be a concern as long as you get as much as you can out and don't have to do major thread repair.
 
+1 on grease.

Also, with a thread chaser, the threads are actually not cut, but rather pushed back in to place. Which means very little shavings, if any at all.

Grease up the tap, run it in a bit, make SURE it's straight, pull it out, wipe off, re-grease, go at it again, repeat as required.

When you shop for a thread chaser, try to find one that fits inside a 5/8" sparkplug socket instead of the one that fits inside a 13/16" because that socket may not actually fit into the plug wells.

I've chased plenty of threads on plug holes, just none on the fzj engines. Good luck!
 
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