2001 C5 Base A4 (96,500 miles)




Went to try and swap spark plug #6 while troubleshooting a small misfire that only occurs when the vehicle is in park but couldn’t remove it. I replaced the spark plugs myself a few months ago and am certain they weren’t cross threaded. Potentially the shop that installed my new harmonic balancer removed them and installed them poorly. Unfortunately that was in Texas and I am living in Virginia Beach so I can’t take the car back there.

The issue that I’m running into is there isn’t enough clearance to seat a socket on the plug to remove it. I’ll attach pictures but they are kind of poor since it’s a difficult angle. The liquid in the pictures is PB blaster that I tried to use unsuccessfully. I’ve tried 5/8” of all varieties and swivels, thin deep sockets, a size up and down, ran a pick around the plug to clear debris (it won’t go around the plug on the side where clearance is limited).

I’m pretty much out of ideas at this point. Also can’t tell if the nut is stripped/rounded or if I’ve never been able to seat the socket because it will grab a small amount and then pop off.

Any help/ideas would be appreciated! Also will accept recommendations for a reputable mechanic in Virginia Beach to look at it.

Hoping to figure this out so I can move on to some fun projects like new valve springs and headers.

Thanks!

 

Definitely doesn't look right.You may try and find someone with a lathe and turn you down a 6 point socket to fit.Then you can see what damage there is.Probably not what you wanted to hear.

 

Based on the picture, and you having previously replaced the plugs with the same tools without issue.....it sounds/looks like the shop cross threaded that spark plug. That is why it is cocked and not centered in the bore. I would try modifiying a 12 point socket, maybe removing ~150ish degrees so you can fit it over 4 or 5 points of the fastner. Slow/straight/steady loosening torque. Good luck.

 

Wow, i wonder how the hell he got that in there.

Im just tossing this out there ,but that line looks like its been JB welded???

Even if you get it out those threads are going to have to be fixed so, if the head has to come off its a good time for a cam.

 

I would hope the picture angle is making that look worse than reality but you could be SOL. I would take a die grinder and thin out a socket to get more purchase on the plug. Then I would keep my wrench very perpendicular to the plug hole and unscrew. If it was too tight I would use my electric impact gun to pulse it out. Impact tools place and remove fasteners with different force profile on the parts. That plug looks cross threaded. Your goal now is to remove the plug and minimize damage.

Let's say the previous guy was real idiot and only cross threaded a couple threads. You might be able to broach out the bad part and engage the clean threads. spark plugs are pretty long and if you can get past a few bad threads to engage good threads deeper in the hole you might be OK, You only need to seat a plug and then about 1/2 turn is tight enough. Taking off the exhaust manifold and removing battery might give you better access.

 

If it is bad as it looks, you'll likely need to take it so a machinist to get it running.

I'd pull the head and you might want to pick up some other stock LS1 castings and just have them ready to go when you pull the head. Pulling heads isn't as daunting as it sounds on a C5.

 

Like said previously, modify a spark plug socket to somehow get it in there and on the plug then very carefully try to back the plug out. If only a little then back in a little. Back and forth so to say. If that doesn’t work and you are a pretty good back yard mechanic just pull the head so you can repair or replace. Once the head is on the workbench there will be more options for a lasting repair.

 

When you have successfully removed the spark plug, buy a back tap spark plug repair tool.

 

OP....this ^^^^^^^

 

Thanks all for the suggestions! I won’t be able to get to this for a few days when I’m back at home.

I’m optimistic that I can remove it and use a back tap thread repair tool but mentally preparing to pull the head if needed. I’ll let yall know how it goes!

 

Be careful. If the car runs, take it to a good mechanic.

You will thank me later.

 

Update:

Squeaked in some time before my next trip and was able to get the plug out with an ultra thin socket. It was barely seated and probably 5 threads short of seating against the head. After checking the plug hole with a borescope it would appear that the first two to three threads were cross threaded. Past those everything looks to be in good condition. Hopefully the back tap will be able to chase the original threads and clean up the first two to three. Now I just have to wait for the tool to arrive and try to not fester too much during my trip the next few days.

Please back me up if y’all think there’s anything I’m missing with this.

Hoping this resolves the sporadic misfires in that cylinder and explains the hissing sound I could hear coming from that area when I shut the car off.

 

Well done. I would be sending the pics to the shop that last touched the engine. Back tap is the way

 

good job.. when you back tap it. im sure you know.. LOTs of oil to help keep any flashings
from going down the hole..

 

It's better to put some grease on the back tap as it will hold any bits better than oil.

 

the majority of the threads will just be chased...

 

This is the perfect example of why you must always start the spark plugs (as well as bolts, studs, nuts, lug nuts...) first by hand, so you can feel if there is any binding as well as to know for sure that the threads have been engaged properly. The person at that shop most probably was in a rush (or was inexperienced) and was using some type of a power tool.

 

Why would the shop remove this when replacing a balancer?

 

To protect my fragile ego (just kidding) and prevent too much shop bashing I think this screw up rests solely on me. I was able to get it off by buying the same socket my dad and I used at his house. You live you learn I suppose. I can report that I’ve successfully completed this job several times on my truck and Subaru but must have botched this.

I’m still grateful for the experience and forum support. This is my second C5, bought my first when I was 21 and sadly it got totaled by a drunk driver when it was parked on the street at night. Now almost 16 years later I’m back in a C5 that needs a lot of TLC and I’m using it as my project/hobby car to get my hands dirty and learn as much as I can along the way. Lots of more complicated projects already completed and more to follow. I’ll get this fixed up and then be able to get back after my other projects.

Thanks again for the help yall! Happy new year!

 

Happy New Year