Strange one... spark plug wire came off.
Thread Starter
Racer
Joined: Dec 2010
Posts: 392
Likes: 5
From: Almost Heaven WV
Strange one... spark plug wire came off.
It is a nice dry evening here in Almost Heaven WV, so I went out looking for a new daily driver. Drove 30 miles to the dealer to see what is on the lot. I have a 2010 coupe with 9,000 miles, 6 sp manual and is run fairly easy most of the time with an occasional romp. Had the cruise set at 65 mph all the way to the dealer who was closed for the day and when I got there, I left it idling while I checked out the inventory. I was out maybe 10 minutes and when I got back in, the check engine light was on, same with the stabilty control message and it was running rough. Nursed it back home running rough, it wouldn't even pull 6th gear at 60 mph. Checked the codes with my Diablo Predator and it was a random misfire. I let it cool down a little and pulled off the FRCs and low and behold the spark plug wire on #1 cylinder had come completely off of the coil. Never experienced this one before. Put it back on and reset the codes and it fired right up with no CELs, idled and revved just fine in the garage. What could cause a plug wire to come off while it was sitting idling?, plugs or wires have never been touched. It is all stock except full Magnaflow catback and LS7 intake bridge and stock tune (no Predator). It had me baffled while I drove 30 miles home on 7 cylinders.
Safety Car
Joined: Sep 2007
Posts: 4,359
Likes: 6
From: Los Alamitos California
St. Jude Donor '09
It is a nice dry evening here in Almost Heaven WV, so I went out looking for a new daily driver. Drove 30 miles to the dealer to see what is on the lot. I have a 2010 coupe with 9,000 miles, 6 sp manual and is run fairly easy most of the time with an occasional romp. Had the cruise set at 65 mph all the way to the dealer who was closed for the day and when I got there, I left it idling while I checked out the inventory. I was out maybe 10 minutes and when I got back in, the check engine light was on, same with the stabilty control message and it was running rough. Nursed it back home running rough, it wouldn't even pull 6th gear at 60 mph. Checked the codes with my Diablo Predator and it was a random misfire. I let it cool down a little and pulled off the FRCs and low and behold the spark plug wire on #1 cylinder had come completely off of the coil. Never experienced this one before. Put it back on and reset the codes and it fired right up with no CELs, idled and revved just fine in the garage. What could cause a plug wire to come off while it was sitting idling?, plugs or wires have never been touched. It is all stock except full Magnaflow catback and LS7 intake bridge and stock tune (no Predator). It had me baffled while I drove 30 miles home on 7 cylinders.
San
Burning Brakes
Joined: Nov 2008
Posts: 940
Likes: 1
From: Long Island NY
Try a search. Has happened to several people. My number 3 came off the coil at 300 miles. It did NOT click back on how it should. Part of the terminal that provides for a positive click on to the coil broke off. I would check all your wires carefully. Remove each one, look for broken parts inside the boot, and reinstall making certain you get the click. Possible it just wasn't pushed all the way on during assembly, but my vote is that it was broken during initial assembly and needs to be replaced.
Le Mans Master
Joined: Dec 2004
Posts: 5,493
Likes: 809
From: West coast CA
Try a search. Has happened to several people. My number 3 came off the coil at 300 miles. It did NOT click back on how it should. Part of the terminal that provides for a positive click on to the coil broke off. I would check all your wires carefully. Remove each one, look for broken parts inside the boot, and reinstall making certain you get the click. Possible it just wasn't pushed all the way on during assembly, but my vote is that it was broken during initial assembly and needs to be replaced.
Racer
Joined: Sep 2007
Posts: 430
Likes: 10
From: Angier, NC
I had 3 loosen up and come off one time. The engine got hot ...it was about 95 degrees in Chapel Hill on Franklin St in stop and go traffic. There was no where to pull over. On star people asked if I wanted to have it towed to a Chevy Dealer. What a mess!. I Took off the Covers and much to my surprise the plug wires were coming out of the Coil Packs!
Advanced
Joined: Jul 2010
Posts: 67
Likes: 0
From: Austin TX
I had 3 loosen up and come off one time. The engine got hot ...it was about 95 degrees in Chapel Hill on Franklin St in stop and go traffic. There was no where to pull over. On star people asked if I wanted to have it towed to a Chevy Dealer. What a mess!. I Took off the Covers and much to my surprise the plug wires were coming out of the Coil Packs!
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Advanced
Joined: May 2013
Posts: 73
Likes: 0
That hapenned to my 10k miles 2010 C6 Z06 just today. Check engine light and stability control light both on and message about the latter. Engine was working...not right.
Well, when I bought the car 2 years ago with 5K miles, the same thing happened at the shop that imediatly located and simply put the wire back on.
So today, when I saw what was going on I stopped and saw one spark plug wire off. Put it back and it's done.
But now I'm in the Forum to know why!
I'll look for corrosion, replace the wires and use the dielectric grease.
2 questions:
-How I know if the coils failed?
-Is it necessary to upgrade the wires or best to use OEM? Katech is too expensive! But there is LG and MSD for what I read. What is the best?
Well, when I bought the car 2 years ago with 5K miles, the same thing happened at the shop that imediatly located and simply put the wire back on.
So today, when I saw what was going on I stopped and saw one spark plug wire off. Put it back and it's done.
But now I'm in the Forum to know why!
I'll look for corrosion, replace the wires and use the dielectric grease.
2 questions:
-How I know if the coils failed?
-Is it necessary to upgrade the wires or best to use OEM? Katech is too expensive! But there is LG and MSD for what I read. What is the best?
Last edited by MarMPB; Sep 22, 2013 at 11:48 PM. Reason: error
Melting Slicks
Joined: Feb 2008
Posts: 3,248
Likes: 4
From: Palm Beach County, Florida
It is a nice dry evening here in Almost Heaven WV, so I went out looking for a new daily driver. Drove 30 miles to the dealer to see what is on the lot. I have a 2010 coupe with 9,000 miles, 6 sp manual and is run fairly easy most of the time with an occasional romp. Had the cruise set at 65 mph all the way to the dealer who was closed for the day and when I got there, I left it idling while I checked out the inventory. I was out maybe 10 minutes and when I got back in, the check engine light was on, same with the stabilty control message and it was running rough. Nursed it back home running rough, it wouldn't even pull 6th gear at 60 mph. Checked the codes with my Diablo Predator and it was a random misfire. I let it cool down a little and pulled off the FRCs and low and behold the spark plug wire on #1 cylinder had come completely off of the coil. Never experienced this one before. Put it back on and reset the codes and it fired right up with no CELs, idled and revved just fine in the garage. What could cause a plug wire to come off while it was sitting idling?, plugs or wires have never been touched. It is all stock except full Magnaflow catback and LS7 intake bridge and stock tune (no Predator). It had me baffled while I drove 30 miles home on 7 cylinders.
#5 coil wire just disconnected after a quick (not panic) stop.
Foolishly checked scanner first and freaked a little before getting smarter and going old-school to check ALL of the connections.
All is well and car runs great now, but IMHO it's an odd thing to happen to any car, much less a 5 yr old with a low clock.
Melting Slicks
Joined: Dec 2006
Posts: 2,694
Likes: 106
. Not thrilled having to spend in stuff like that, but I felt wires and a catch-can were necessary expenses for the good of the engine 
. But to each his own, of course.
Navigator
Joined: Aug 2016
Posts: 9
Likes: 0
Plug wires pop off
In my days of dyno testing engines (30+ years) we saw this happen. It is the air trapped inside the boot expanding and popping the wire off. The fix for this was to put an air bleed (small tunnel) the length of the boot to allow air to pass. Hot idle conditions are one of the worst for this. Do all spark plug wires have these air bleeds? I have no idea. The better ones should. Keep in mind, even if it has the air bleeds they can become plugged. Just saying...
It is a nice dry evening here in Almost Heaven WV, so I went out looking for a new daily driver. Drove 30 miles to the dealer to see what is on the lot. I have a 2010 coupe with 9,000 miles, 6 sp manual and is run fairly easy most of the time with an occasional romp. Had the cruise set at 65 mph all the way to the dealer who was closed for the day and when I got there, I left it idling while I checked out the inventory. I was out maybe 10 minutes and when I got back in, the check engine light was on, same with the stabilty control message and it was running rough. Nursed it back home running rough, it wouldn't even pull 6th gear at 60 mph. Checked the codes with my Diablo Predator and it was a random misfire. I let it cool down a little and pulled off the FRCs and low and behold the spark plug wire on #1 cylinder had come completely off of the coil. Never experienced this one before. Put it back on and reset the codes and it fired right up with no CELs, idled and revved just fine in the garage. What could cause a plug wire to come off while it was sitting idling?, plugs or wires have never been touched. It is all stock except full Magnaflow catback and LS7 intake bridge and stock tune (no Predator). It had me baffled while I drove 30 miles home on 7 cylinders.
Pro
Joined: Jan 2003
Posts: 612
Likes: 69
From: Southwestern PA
This happened to me last summer. Number 5 popped off but not enough to notice. Started nursing it home and finally pulled over, opened the hood and see #5 is off. Reconnected and all was well.
Periodically I give all 8 a push at both ends.
Periodically I give all 8 a push at both ends.
Race Director
Joined: Dec 2013
Posts: 12,504
Likes: 3,631
Trapped air in the boot that expands as it get hot.
The cure, use a light coat of dielectric grease on the inside of the boots before you install the wires. The grease allows for the air to escape , plus allows for the boots to be installed so you are sure that you have the connectors snapped in place as well.
The cure, use a light coat of dielectric grease on the inside of the boots before you install the wires. The grease allows for the air to escape , plus allows for the boots to be installed so you are sure that you have the connectors snapped in place as well.
Burning Brakes
Joined: Dec 2011
Posts: 876
Likes: 116
From: HOMESTEAD FL
I had one come off... thought I had broke the car... LOL I was on my way to a "Corvettes of Miami" club meeting and one of the guys knew exactly what it was... sure enough, popped the hood and one wire was not connected. What a relief!
SPEED SAFE, NICK
SPEED SAFE, NICK
