so i took the car to New England Dragway yesterday for their last import event of the year. lots of v8 classes were running as well which was weird, but good - without the v8's there the track prep is usually sub-par for import events. my friend matt (high_body on this forum) came along and shot some videos. they should be up later in the week. this was my first time at the track since october 09 when i ran the 11.87. passes ranged from a 12.5x to a 12.15, not counting my last run which was a 15.5 but i'll get to that...
on my 2nd to last run (12.15) the car misfired just a little, during the top ~1/3 of 4th gear. it seemed to be running, idling fine on my way back to the pits, so i decided to keep racing in the next round. lined up this time without launch control and cut a 1.85 sec 60' time, my best of the day. ripped through 2nd gear and into 3rd, that was when i noticed it was misfiring like crazy. let off around 1/3 track (i shift to 4th around 1/2 track) and coasted in for a 15.5 at 60mph
. the misfire continued (although obviously less noticeable) at light loads and even idle.
let it cool off, checked the plugs and my #4 plug was in really tough shape. the ground electrode was, well... gone (i'll post a pic). not sure if it came off in one piece or eroded away slowly. lots of spatter on the plug from what must have been pretty serious detonation
. not sure what the cause is yet, i'm thinking maybe a partially clogged injector? plugs 2 and 3 looked completely normal, although the top of piston #3 looked a little wet. could have been residual fuel from when i shut it down, could also have been oil, not sure. the plug in cyl 1 also looked like it got too hot, the tip of the ground electrode looked slightly melted and the piston top was smooth and mostly clean (unusual, usually they have a light coating of carbon). 1&4 are on the same coil pack, not sure if that means anything or not.
i got a used plug from one of the faster honda teams (9-10 second car that changes plugs all the time) and made the 2 hour drive home. at this time the engine is not smoking or misfiring at all and ran fine the whole way home, although i obviously took it pretty easy.
next up... prognosis. i talked to a friend last night about borrowing a bore scope. his father is a mazda master tech/instructor, and he has access to all kinds of special tools, including a bore scope. they used it on his mazdaspeed protege a while back. i'll also do a compression test, and pull the turbo to check for damage to the turbine blades. depending how all of this goes i may need to pull the head (ugh).
on my 2nd to last run (12.15) the car misfired just a little, during the top ~1/3 of 4th gear. it seemed to be running, idling fine on my way back to the pits, so i decided to keep racing in the next round. lined up this time without launch control and cut a 1.85 sec 60' time, my best of the day. ripped through 2nd gear and into 3rd, that was when i noticed it was misfiring like crazy. let off around 1/3 track (i shift to 4th around 1/2 track) and coasted in for a 15.5 at 60mph
. the misfire continued (although obviously less noticeable) at light loads and even idle.let it cool off, checked the plugs and my #4 plug was in really tough shape. the ground electrode was, well... gone (i'll post a pic). not sure if it came off in one piece or eroded away slowly. lots of spatter on the plug from what must have been pretty serious detonation
. not sure what the cause is yet, i'm thinking maybe a partially clogged injector? plugs 2 and 3 looked completely normal, although the top of piston #3 looked a little wet. could have been residual fuel from when i shut it down, could also have been oil, not sure. the plug in cyl 1 also looked like it got too hot, the tip of the ground electrode looked slightly melted and the piston top was smooth and mostly clean (unusual, usually they have a light coating of carbon). 1&4 are on the same coil pack, not sure if that means anything or not.i got a used plug from one of the faster honda teams (9-10 second car that changes plugs all the time) and made the 2 hour drive home. at this time the engine is not smoking or misfiring at all and ran fine the whole way home, although i obviously took it pretty easy.
next up... prognosis. i talked to a friend last night about borrowing a bore scope. his father is a mazda master tech/instructor, and he has access to all kinds of special tools, including a bore scope. they used it on his mazdaspeed protege a while back. i'll also do a compression test, and pull the turbo to check for damage to the turbine blades. depending how all of this goes i may need to pull the head (ugh).
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