Well the old 89 hatchy is having problems again already. I got a CEL, turned out to be a O2 sensor code. So I went to check the spark plugs and found this...



I had just checked them 1000 miles before this and they were fine. When I backed them out the corroded/melted part on the last threads there damaged the threads in the head. I managed to get new spark plugs back in, but I'm scared that if I ever take them out again the head will be scrap. Also, oil started leaking down into the spark plug tubes from above. Under load I can't hear any pinging at all. I checked the timing and it was at 16 BTDC. I also ran a bottle of Techron fuel injector cleaner through it about a week ago. I was hoping to get at least another 15,000-20,000 miles out of this motor and then swap in a Z6/Y8.

Also I forgot to mention I managed to get compression numbers on #1 and #4 because the threads were good still. I got 127 and 185. 185 is good, 127 just above the minimum, but with way too much variation.


What could be causing the lean condition or detonation?




Modified by RyanCivic2000 at 10:33 AM 1/14/2004

 

Bump, pic fixed!

 

a bad O2 will make engine run on a limp mode
wich can cause a bad fuel air mixture
along with bad compression and leaking oil , can defenetely cause detonation
what we see there was a result of excesive heat and detonation on a minimal damage

i say we gotta get that Z6 soon!

 

Well, I need it to last 6 months, because right now all my money is going towards my turbo project for my 2000 coupe.

 

Looks more to me that your 02 failed resulting in a rich mixture....

Now thats just an assumption going off the plug...see how its all black, thats a good indicator, was there much soot on it?

if it was lean and close to detonating it would be white as hell.....

I guess my assumption doesnt explain why the threads were melted/toasted, sounds like that would be from overheated combustion temps.....but then that would disregard my idea, since running rich means cooler combustion temp.

I would do a tuneup, and change the o2

 

My guess is that its not detonating all the time and at the time I shut it down and pulled the plugs it may have been running richer which is why the plugs aren't scorched white. The black speckles on the porcelin are usually a sign of detonation or pre-ignition.

 

Did you replace your o2 sensor yet?