92 nissan 240sx

So I'm driving on the highway normal as can be and I feel a loss of power along with some vibration. I figure my coil connection had come loose as it has done before except this time, I hear a sound like a small metal piece of something being banged around some of the internal assemblies. The banging is intermittent and not happening as quickly as the pistons are going through their strokes. I stop and find that cylinder 4's spark plug has been pockmarked all over and the tip has been pushed right onto the electrode (no more spark, obviously). So I re-gap it, take it around the lot one time to work out the misfires, and I'm on my way again.

As I'm driving to work, I lose power again along with the engine vibrations. When I get off work, I check the spark plugs again and the same thing has happened. Except now it happened to cylinder 3's spark plug! The ceramics surrounding the electrodes on #3 and #4 are browned much moreso than #1 and #2. All spark plugs are under a month old.

I replace the spark plugs thinking MAYBE Autozone gave me the wrong spec plugs. New plugs are pretty much the same length but I go ahead and give them a try. The battered older ones are Coppers (Autolite). New ones are the usual run-of-the-mill type plugs (Denso). The new plugs work fine for the ride home, then the car starts misfiring again. I remove all plugs and turn the engine a couple times to force out any foreign objects; nothing came out, as far as I saw.

Replaced the spark plug wires (they ARE a bit old) and the car does well for the 45 miles to and from work, but the misfiring started back up again today. Plug #4 is slammed tip-to-electrode in addition to the metal clanking again. I re-gap and get back home with little drama.

The plug bending has happened about 5 times over the week. It was spark plug #4 all but one the one time.

What could possibly be happening?!? Valves getting stuck and piston slamming it up to the spark plug? Rod bolts backing out? Rod bearings disappeared? What could explain it happening to two different spark plugs?

Engine has not jumped timing because it still pulls like usual when running all 4 cylinders

[Edited on February 9, 2007 at 2:29 PM. Reason : +]

2/9/2007 2:25:44 PM

WEIRD

2/9/2007 2:34:33 PM

could be a number of things. either way, it's not smart to keep driving it.

doubtful it's any lower end bearings, you'd hear a consistent knock. off hand, it sounds like one of three things:

1.) you've stretched a con rod and it's letting the piston just hit the plug.

2.) there's a foreign object in the cylinder (sounds the most likely from what you've described)

3.) you've got a really worn wrist pin (you'd most likely get a constant noise with this also though).

either way, you need to pull the head and check things out. you could do much more extensive damage if it's just a piece of a screw or something like that in there. good exscuse to do the t-belt, oil pump, water pump, etc... maybe get the head redone also. it's definitely possible you already did bad damage to the piston, or that the foreign material is actually a corner from the piston, an upper ring, etc. then a full rebuild or motor swap is in order.

i've heard of really bad misfiring/predetonation causing plugs to do that, but i've never witnessed it first hand...


[Edited on February 9, 2007 at 3:09 PM. Reason : do a compression/leakdown first!]

2/9/2007 3:01:50 PM

just get a new motor



i cant believe you said "con rod" ivan, thats so jj-esque

2/9/2007 3:15:58 PM

lol. exscuse me, CONNECTING rod.

DO AN SR20DET SWAP FTW!!!11

[Edited on February 9, 2007 at 4:06 PM. Reason : .]

2/9/2007 4:06:10 PM

sounds exactly the same as this:

http://forums.vwvortex.com/zerothread?id=3055635

[Edited on February 9, 2007 at 4:21 PM. Reason : ended up being a broken exhaust valve]

2/9/2007 4:21:00 PM

lol, those are some scared bitches of warranty claims.

i thought possibly a broken valve also, but unlikely considering he said it ran normal for a while when he replaced the plug.

i'd still do a compression/leakdown for the hell of it first though.

2/9/2007 4:33:58 PM

I believe there was someone on CN selling a KA for a decent price might want to check that out. On CN smiz sounded pretty sure that it was detonating which could be a possiblity.s Also sparkplug wise I run NGK (which is oem on our cars) and have never had a problem - Autolite is garbage.



[Edited on February 9, 2007 at 5:02 PM. Reason : sd]

2/9/2007 4:59:09 PM

^yeah, i wouldn't run anything else in a jap motor...

2/9/2007 5:02:06 PM

no SR swap for me

no silly NA stock engine from CN

I've got a bigger surprise for yall. But until then (next week), I'd still like to have my car up and running. Don't want to lay the 230k engine to rest nearly dead

2/9/2007 6:04:26 PM

ka-t?

rb?

just keep driving it then. maybe you'll get lucky and whatever might be in there will come out. or maybe it'll blow.

2/9/2007 6:07:59 PM

it's the engine in this little guy:
http://www.youtube.com/watch?v=9I5TViZKutw

I used to like the idea of an ongoing project.. but you know.. fuck it. drop in and go. complete setup (yes, full standalone too) minus tranny.



as far as the misfiring crap. I snaked a telescoping magnet down into the chambers through the spark plug holes but got nothing. I inspected everything, put it all back together, and just ended up retarding the ignition timing a bit.

Some guy mentioned that extreme pressure waves from detonation could pinch a spark plug gap shut like that. Eh, I'll take anything for now.

[Edited on February 9, 2007 at 6:16 PM. Reason : ]

2/9/2007 6:11:52 PM

Does Matt Martin Drift car have a KA-t in it? I forgot. I remember him talking about a t3/t4. That's a nice setup if that's what you were thinking. Just don't do a bottom mount mani - biggest PITA ever.

[Edited on February 9, 2007 at 7:03 PM. Reason : sd]

2/9/2007 6:59:52 PM

single cam ka FTMFW niggas

2/9/2007 7:12:35 PM

Yeah, if you want a 17 year old engine

2/9/2007 9:55:41 PM

totally thought that said mark martin..

2/9/2007 10:10:45 PM

I have a spare 600rr engine you could drop in it... prolly has same powr!!! :p

2/9/2007 11:00:26 PM

mark martin could drift better

2/9/2007 11:12:22 PM

yeah i'd take a 17 yr old engine

2/9/2007 11:12:37 PM

The KA isn't exactly an RB (i wish it was)

2/10/2007 12:00:54 AM

just go get urself a new truck engine no biggie.

2/10/2007 12:17:12 AM