slight misfire - need help

moose.cannon · Post by **moose.cannon** » Sun Aug 22, 2010 4:50 pm

Hi guys,
Now I'm no mechanic but know enough about cars to be dangerous.
While my levin is in the shop getting fixed I'm driving around a SSS U12 with an SR20DE. It's recently developed a bad misfire. At first it started off missing every now and then under load at about 2-3000rpm then it quickly got to the point where it was pretty much only running on 3 cylinders. I replaced the spark plugs to no avail, I replaced the dizzy cap, no luck there, there was what looked like rust on the dizzy rotor (i think that's what it's called) so I gave it a very light sand, not sure if that was a good idea or not? feel free to tell me off for doing it lol, anyway that didn't work... then (silly me for not checking) discovered oil in the end of spark plug lead no.1, I had some old leads (not sure if they were good) so I replaced the current leads with the ones i had lying around. Now she runs on all 4 cylinders at idle, however under load she misfires quite a bit. Any idea's on what I can try next?

BZG Wagon · Post by **BZG Wagon** » Sun Aug 22, 2010 5:06 pm

You've done the dizzy & plugs - are leads the next thing worth trying? Cracked lead shorting?

If you unplug one cylinder at a time you should be able to work out which one is causing the issue. Measuring the resistance in the lead can also tell you in some, but not all cases.

Oil at the end of the lead could just be the gasket under your rocker cover(?) leaking - fairly common especially on old cars. If it's not heaps it shouldn't be a problem.

moose.cannon · Post by **moose.cannon** » Sun Aug 22, 2010 5:23 pm

Thanks,
Is trying a combination of different leads a bad idea? the set I removed were red 'high performance' leads, the ones I replaced them with are standard black ones which look slightly thinner.

BZG Wagon wrote:If you unplug one cylinder at a time you should be able to work out which one is causing the issue.

Will this help if there appears to be no misfire at idle?

also, is spraying crc on the contacts at both ends of the leads a good idea?

Cheers

nile · Post by **nile** » Sun Aug 22, 2010 10:50 pm

Don't use crc (assuming you mean lubricant like WD40?). You want a contact cleaner that will wash off any conatminants then evaporate for that type of job.

If they are looking dirty just use some sand paper to get some clean metal on them then give it a blast with contact cleaner if you have some. I'm not sure how effective that will be but that's generally how you clean a contact.

cedwards · Post by **cedwards** » Sun Aug 22, 2010 11:07 pm

sounds like bum leads to me

moose.cannon · Post by **moose.cannon** » Sun Aug 22, 2010 11:18 pm

cool thanks for the info.

I'll grab a new set of leads 2morrow, hopefully it solves the problem.

moose.cannon · Post by **moose.cannon** » Wed Aug 25, 2010 3:57 pm

got new leads, had to wait for studylink for some mula. replaced the leads and seems to hav fixed the misfire. However she doesn't seem to have as much power as she used to, especially from 0 to 3000 rpm. is this a timing issue?

BZG Wagon · Post by **BZG Wagon** » Wed Aug 25, 2010 7:13 pm

moose.cannon wrote:got new leads, had to wait for studylink for some mula. replaced the leads and seems to hav fixed the misfire. However she doesn't seem to have as much power as she used to, especially from 0 to 3000 rpm. is this a timing issue?

Glad to hear it's sorted.

Are you sure you didn't have flat spot somewhere before you changed the leads etc?

Smooth acceleration normally 'feels' slower than something with a bit of hesitation along the range.

moose.cannon · Post by **moose.cannon** » Wed Aug 25, 2010 8:28 pm

I'm pretty sure there's not as much power as there used to be, pulling out into traffic and putting my foot down feels different, there's also this hill with a passing lane that I drive a lot and can usually make it up the hill doing 110km/h in 5th and can even slightly gain speed, now when driving up the same hill in 5th doing 110 I lose speed ever so slightly, end up doing about 100 by the time I hit the top. Is there anything that I can check further? or is it possible that driving with a misfire had done some damage to my engine? I'd love to get the timing checked but poor student here will have to save his penny's

FULLOC · Post by **FULLOC** » Thu Aug 26, 2010 7:58 pm

rocker cover seals leaking oil around the plugs?

moose.cannon · Post by **moose.cannon** » Thu Aug 26, 2010 8:24 pm

FULLOC wrote:rocker cover seals leaking oil around the plugs?

that was the initial cause of the problem, but after replacing the plugs and cleaning the spark-plug wells out no oil has re-appeared yet

Flannelman · Post by **Flannelman** » Wed Sep 08, 2010 9:43 am

Check plug gap? Close them up to 1mm and see how it goes

moose.cannon · Post by **moose.cannon** » Tue Oct 12, 2010 11:25 am

all sorted for now _b