Anyone ever hear of spark plugs backing out?

[squarelogo]

My wife was driving our 2005 Pilot (96,000 miles) yesterday and when she was returning home, the CEL and VTM-4 lights came on and the vehicle started shuttering/misfiring.

I read some posts here and thought that it could have been the EGR. Since the dealer charges $135 just to open the hood, I figured I'd take the chance and just replace the EGR for $80. I installed the new EGR, reset the ECU, and started the car, still misfiring and running rough.

I thought I'd just drive the mile or so to the auto parts store and run their scanner to find out what codes we were getting. A block away from the auto parts store I heard some popping/snapping from under the hood and a nasty electrical burning smell and then when I pulled into the parking lot it dies and would not restart.

I ran the scan and came up with codes for a misfire on almost every cylinder.

Called roadside assistance and got it towed to the dealer. The dealer called this afternoon and told me that two of the spark plugs had backed out and caused some arching and burnt up two of the coil packs.

The service guy said it would be $680 for their diagnosis, new plugs all around, and two new coil packs. That may or may not be the end of it, he did mention it was possible that I would need a new head.

He also said that it's not that uncommon to see plugs back out. Has anyone on the boards here heard of similar issues?

[nuthineasy88s]

I've seen it before but I wouldn't say it's common at all. Unless they have been changed and not put in properly. Usually the only time I see it is on a used motor, seen a few guys put them in start them up and have it ticking or hissing like an air leak. found the plugs loose from the salvage yard.

[squarelogo]

These plugs haven't been touched since the vehicle was new.

The dealer said that one plug hole was stripped clean and they tried to do a helicoil. For whatever reason that did not work. Now they want to pull the head and take it to a machine shop to check all the valves.

They want another $1000 for that service with zero guarantee that this will fix the problem. Their other option is to spend $6300 on a new motor.

I'll be picking up the car soon and finding a new shop. I have seen used motors for around $1500. I'm certainly not paying 4 times that amount. Mostly because I can't afford it.

So damn frustrated right now. I bought this vehicle because I thought it would be reliable for many many years. The used car manager talked me out of an extended warranty when I bought the car three years ago.

[rocky]

Sounds like something happened in this car's prior existence that isn't good....

And sadly they covered it up and sold you a pup.

That really sux

[3rdrow]

if it was me, i would try to replace the plugs myself first and plug the original coil packs back in and try to fire it up and see what happens.

[samc]

I've seen where spark plugs have come loose but the only damage was a misfiring car. ... Where you would re-seat the plugs/ignition coils and be done with it.

Did the dealership show you these plugs and ignition coils? Don't yell at me but it sounds like they're trying to hose you.

IF!!!! (big IF) one of the holes on the cylinder head is stripped out and jerry rigged then why couldn't you buy a used head off a junkyard (and new head gasket ofcourse) and have that installed with new plugs and whatever ignition coils might have been damaged.

Just on a short google the heads are $100 or $80 depending on which one you need.

I really think you should get a second opinion.

[squarelogo]

I'm going to pay the nearly $900 to the dealer for their initial attempts to fix this and take the car home. I haven't figured out what to do yet.

Might take it somewhere else and buy a used head.

Might just buy a used motor and try and find a good mechanic to install it.

Might light it on fire.

[squarelogo]

Went to talk to the service adviser today and got a little more info.

When one plug backed out and sparked, it "blew up", sending the electrode down into the motor. They did retrieve that piece, but they don't know how much damage was done. The car was driven about 3 miles after the CEL was on, and based on my observations, maybe 1/4 of a mile after the plug "blew up".

They said one of the valves on that cylinder is not operating correctly. They said it's drivable, but obviously misfiring on one cylinder.

They also said that one of the other spark plugs was very loose.

I'm not confident with the dealership. They have been pushing me towards expensive repairs and saying contradicting things.

My plan at this point is to replace/repair the bad head, which I may attempt myself, or find another shop that knows how to fix things, instead of just replace things.

[John M]

Sounds like you are hosed.

1. The head just doesn't strip itself where the plugs go in. Obviously they had been out at some point in their life. Someone put one in wrong and stripped the hole.

2. If debris goes down into the hole...thats on top of the piston. So that piece gets hammered into the backside of the head, possibly pinched between the valves and their seats, bends valves, breaks compression rings on pistons, dings the top of the piston making 'hot spots', and if big enough bends rods.

3. A compression and leak down test on that cylinder will tell the extent of the damage. Easy and cheap to do. Frpm your description, sounds like they did that and you have bent valves on that cylinder....meaning you must pull the head and replace with a good used one or rebuild the beat up one. What were the compression numbers on that cylinder dry? If below 90 you are toast, if below 110 you have issues.

4. Never heard of a plug exploding the electrode. Seen the ceramic tops break apart though.

5. Who had the plugs out? That is who is ulitimately at fault. Again, can't have a stripped hole without someone tinkering there.

Hope it all works out for you. I'd be shopping for parts.

[archie]

Spark plugs popping out of the heads is a known issue.

"Ok here's the story....Spark plug exploded. Pieces from the plug went into the cylinder and damaged the piston and cylinder to the point of needing a new engine."

"Got quotes for used engines - installed price
-46k engine - $3050
-83k engine - $2800"

Engine malfunction light flashing - Honda Odyssey Forum : Odyssey Minivan Forums

Spark Plug Exploded - Honda Odyssey Forum : Odyssey Minivan Forums

One of my sparkplugs is gone! - Honda Odyssey Forum : Odyssey Minivan Forums

[John M]

I was just about to say no way...but that post "One of my Spark Plugs is gone" points to a manufacture defect in the head from new. And Honda has been covering it out of warranty. Its a big stretch with your mileage, but I would certainly talk to the Honda DM about getting some help if you are the original owner, and if you or anyone other than Honda haven't touched the plugs.

[Underdog]

Plugs "Backing Out" does happen, but usually when mechanics hand tightened the plugs and then "Forget" to torque them.

Either way , sloppy workmanship, which unfortunately seems to becoming normal at many Honda Dealerships.

[mclairmo]

Spark plugs will stay put if installed correctly. However, if installed loose, then they can back out and yes, when they back out, hot combustion/exhaust gases will escape past the threads and can blow those soft aluminum threads in the head away completely. Would not happen with cast iron heads, but the soft aluminum threads in an aluminum head will get burnt away and then the plug blows out. Sounds like the plugs were replaced in the past and not tightened enough. The bad head needs to be pulled and repaired or replaced. Valves need to be checked and or repaired. Cylinders and piston tops need to be checked for debris, scoring and other damage. If the cylinders and piston tops are ok, then put back the repaired or new head and you are done.

[hondacuraplanet]

Originally Posted by mclairmo

Spark plugs will stay put if installed correctly. However, if installed loose, then they can back out and yes, when they back out, hot combustion/exhaust gases will escape past the threads and can blow those soft aluminum threads in the head away completely. Would not happen with cast iron heads, but the soft aluminum threads in an aluminum head will get burnt away and then the plug blows out.

I dunno. I actually used to get loose spark plugs all the time in a 361 Y block Ford V8. It had about 80K on the odometer. I'd hear some horrible rattling coming from the engine, and I'd have to retighten one or two of the plugs. One can only speculate how that condition came about.....

[mclairmo]

I have never seen a properly installed plug back out all on its own. Not saying it cannot happen. Just have not seen it happen in 24 years of wrenching on all kinds of cars and trucks, import and domestic. However, your story makes me want to check all my plugs now. Thanks for making me paranoid now.