Bad Craziness with my engine (piston hit the spark plug) Any Ideas?

[paulviriyapan]

This is what happened:
I took my car to the Acura dealership. They took a look at the engine and found one of the coils completely destroyed. Apparently what happened was one of the cylinders came up too high and hit the sparkplug, shifting that up the head and shattering the coil. They took off the oil pan and looked at the crankshaft. So far the crankshaft and pistons arms look fine. They have yet to take off the heads and take a look at the upper block. When they take the head off theyll inspect that to see if the problem lies within there, otherwise theyll just send it into a shop to repair the sparkplug threads.

Right now, neither myself nor Acura Dealership have any idea what happened to it. Mechanic said that he has never seen anything like this. If anyone has any ideas on what may be going on, I'm open to any suggestions! Thanks.

 

[nsxtasy]

Ask them if they've called Techline (the service at Acura HQ for when dealer service departments don't know how or why something happened).

 

[Soichiro]

>>Apparently what happened was one of the cylinders came up too high and hit the sparkplug,

I believe you mean one of the pistons came up too high. But the piston is connected to the crank very solidly, and the crank rotates inside the engine case within very small tolerances. I don't think a piston could move very far without destroying a connecting rod or the crankshaft.

Since this did not happen (according to your post) I think a spark plug may have come apart or elongated some how, was then hit by the piston and travelled up into the coil. Are you using OEM sparkplugs or some aftermarket version?

If disassembly shows no damage to internal engine components then the proposed fix of re-threading the spark plug hole sounds OK.

 

[paulviriyapan]

Thanks for the reply. I posted another thread regarding the latest news on the damage. We now suspect that the timing belt skipped a tooth or two (pershaps of bad tensioners) and the piston hit the valve which hit the spark plug. Right now I'm shopping around for places to rebuild the head.

 

[Daria]

If there was PHYSICAL CONTACT between the top of the piston and the underside of the spark plug, your problems are not as simple as repairing the spark plug threads. You need to find out exactly why (incorrect plug type, lack of proper washers and/or gaskets, mis-aligned crank components – although unlikely for the NSX ???). Then you need to check for damage to the piston itself.

I suspect (and for your sake I hope) that someone over-tightened the spark plug and stripped the threads. Then you drove the S&*%$ out of your car revving it to high rpms. The HIGH COMPRESSION hit the underside of the spark plug, shattering the remaining coils already weakened by the stripping process, and thus no physical contact. Then all you need to do is to repair the threads holding the spark plug.

Interesting problem though, keep us informed of what actually happened.

 

[Briank]

My wild guess is that you dropped a valve and the piston pushed it up into the sparkplug. It is impossible for the piston to hit the sparkplug directly. Has the dealer looked under the head cover ?

 

[paulviriyapan]

No we haven't taken the heads off yet. Due to the very tight clearances of the nsx, the heads can only be taken off after the engine has been taken out of the car. The dealer quoted me $2200 (?!?!) just to take out the engine. Ramon at Niguel Motors quoted me around $800 (so he will get the work). The only thing we know is that we took off the oil pan (and everything underneath) and looked at the bottom end. Everything was fine. (crankshaft, bearings, etc.). We drained and sifted through the oil. There was absolutely no metal shavings fragment in the oil. The only thing we found was "hondabond" sealent.

Before I have Ramon pull the engine, I want to have a borescope done through the spark plug to see if there is any damage to the piston or cylinder wall. If there is then I'm f#@%ed!

Thanks for the posts everyone, I will keep you informed.

 

[Larry Bastanza]

Paul,

Just an FYI, it is not true about head removal. It is possible to be done in the car. Check out http://www.danoland.com/nsxgarage/bent/index.htm

I will say dropping it out will be easier on the back though.

Good Luck, hope your lower end is OK.

The mileage on your car is very important, please comment, especially in regard to the age of the timing belt if this is the issue. We discuss timing belt change intervals all the time and really have only the maintenance schedule as a reference.

Also there are some used engine available at reasonable prices, if required, let's not throw out the baby with the bathwater

HTH,
LarryB