54 replies to this topic

[CORZRYDE]

^ yes it would...

15psi doesn't seem too harsh on a built motor. Hopefully the compression test goes well dude.

[dB_Outlaw]

Thinking its a bad coil (spark) but just been dragging getting it looked at. I'll have to nag my mechanic friend but he'll probably want me to take it to his shop. Don't really want to drive it anyway with it misfiring.

[dB_Outlaw]

Compression Test Results:

Three of the cylinders were reading about 140 and one was 130ish. It seemed OK until we checked online which claims the minimum compression is 150 and recommended was 189. MWR did some "light" head work.

Thoughts?

[Roxtar]

your results are close enough together that if it was lack of compression causing a misfire, you'd be getting them on multiple cylinders.

also, since your engine is running lots of aftermarket bits, the compression spec in the manual likely no longer applies. things like cam timing and overlap, lower compression ratio pistons, etc will skew that figure.

[dB_Outlaw]

So what's left to check? Coil pack spark, injectors fuel pump and booster pump? Misfire seems to happen at idle.

[Roxtar]

this page shows some things that can cause a misfire at idle:
www.wavehook.com/dbase/article.html?article=b5accc327d0f8ab8251468147361873c

injector, leaky valve seal,

[dB_Outlaw]

Got the coil pack bolts re-threaded (stripped two trying to DIY). Ran the car idle for a good 10-15m w/o a miss. Drove the car a few miles. No misses. Seriously wondering why no mis. Maybe a coil pack wire was loose? Going to drive her tomorrow to work and see how she does.

[Twincharged&Auto]

Usually misfiring will be a air leak, bad front 2 sensor, dirty maf. Try unplugging the maf sensor with it running, see if it runs better. Then you will rule out mechanical.

[dB_Outlaw]

Well I spoke too soon. Drove it to work today and it misfired about halfway. Misfired stayed until I parked it. Not sure if I should attempt to drive it home if the misfire sticks when I restart it. About a 10m drive.

[Twincharged&Auto]

Did you try what I wrote????

[dB_Outlaw]

not yet.

[Twincharged&Auto]

It takes no time, leave it idling and unplug the maf, see if it smooths out. After that, check the plugs! What kind of plugs are in it? Copper or Iridium?

[dB_Outlaw]

plugs were already replaced (the old ones were OK); that was the first potential fix. I used NGK Iridium. Compression test also checked out OK.

[Twincharged&Auto]

Ok, so then go start it and unplug the maf, report back with what happens.

[dB_Outlaw]

Couldn't even find the damn MAF sensor. I know it should be on the air intake. Regardless, I had an ex-mechanic co-worker look at it and we determined cylinder 1 (?; closest to the oil cap) isn't firing at all. No Spark coming from the ignitiion coil. HIs prognoises was either the ignition harness was bad or an issue with the computer not sending spark. Knowing my luck, it's the later. Just going to gimp it home this afternoon before traffic gets too bad.