How To Fix Missfire Problem

[shnaped_second]

Ripped out my coils today and had a look, they seem to be fine, couldnt find any cracks, they looked brand new basicly and the plugs looked fine to but still has a miss

[MKDR33]

well you think that is problems, READ THIS, got new splitfires and no differance, must be something else, BUT WHAT?

if its not a coilpack problem, it might be your spark plugs needing to be regapped or it might be an AFR issue..

[MKDR33]

Ripped out my coils today and had a look, they seem to be fine, couldnt find any cracks, they looked brand new basicly and the plugs looked fine to but still has a miss

i dont have much experience with R34 GTT coilpacks dude, but you could try taping up across the middle of the coilpack as described (shown) on page 1 of this thread and see how u go..

you CANT really see the hairline crack on the coilpacks, but its there and is the cause of the missfire in most cases.. if this isnt the case, then you might need to regap your spark plugs to 0.8 and check that your AFR isnt running too rich..

[shnaped_second]

i dont have much experience with R34 GTT coilpacks dude, but you could try taping up across the middle of the coilpack as described (shown) on page 1 of this thread and see how u go..

you CANT really see the hairline crack on the coilpacks, but its there and is the cause of the missfire in most cases.. if this isnt the case, then you might need to regap your spark plugs to 0.8 and check that your AFR isnt running too rich..

Plugs are allready gapped to 0.8 running stock ecu, the thing is one week it will miss then the next week it will be fine, so im not sure if its the CAS as some ppl have said they had troubles with it

[markimak]

pulled coils out of the R34 tonight. cant see any cracks..

will be putting silicon on tomorrow. anyway. my question is. do u put silicon on the rubber boot and wher it connects to the coil? smuther the whole thing?

[markimak]

damn paid $13.45 at true value.. i aint travelling to bunnings another 15kms away to save $2.45

pulled them out 2 nights ago upon inspection none had vissible signs of cracks or marks.. so i decided to bast them with silicon 401 as a DIY thread suggested. waited a night and put them in.

started it up warmed her a bit. and took her for a drive still had miss. but it was more upwards of 6000rpm.. had more lower down torque. but still wasnt fully driveable.

parked it in the driveway.. gave it a free rev held it at 4k to see if it would splutter. and it didnt. then took it for a drive again and it was better. came back. decided that i would try to cool the intake temps to limit chances of detonation.. so i threw some cold water on the SMIC and took her for a drive. revs fine all the way to 5500 and cough and then to redline..

after a while it ended up fixing itself..

now my guess is the ECU adjusted itself a littlebit as it went on. or due to lower air temps ther was less pinging and it helped out. thus cleaning out any hot spot carbon deposits from the head leaving it clean..

sound right..?

[r33gts]

lets hope this works, its gonna save me lots of $$$, in that case i'll shout u's all drinks, coronas all round

great post, thanks

[MKDR33]

damn paid $13.45 at true value.. i aint travelling to bunnings another 15kms away to save $2.45

pulled them out 2 nights ago upon inspection none had vissible signs of cracks or marks.. so i decided to bast them with silicon 401 as a DIY thread suggested. waited a night and put them in.

started it up warmed her a bit. and took her for a drive still had miss. but it was more upwards of 6000rpm.. had more lower down torque. but still wasnt fully driveable.

parked it in the driveway.. gave it a free rev held it at 4k to see if it would splutter. and it didnt. then took it for a drive again and it was better. came back. decided that i would try to cool the intake temps to limit chances of detonation.. so i threw some cold water on the SMIC and took her for a drive. revs fine all the way to 5500 and cough and then to redline..

after a while it ended up fixing itself..

now my guess is the ECU adjusted itself a littlebit as it went on. or due to lower air temps ther was less pinging and it helped out. thus cleaning out any hot spot carbon deposits from the head leaving it clean..

sound right..?

usually the pinging occurs in winter at cooler temps, the rest sounds right..

[markimak]

but the hotter intake temps i think made it miss and having the cold water on helped it cool.. and cleaned out the cyl heads..

anyway.. good stuff on the silicon stuff.

[r33gts]

ok. i did mine it works!!! although still coughs at about 5000, and doesnt have the same power like it used to when the boost kicks in, but much better than before, it was impossible to drive, now im thinkin it could be the plugs since i didnt put them in and i dunno what gap is it set at

[markimak]

so are u gonna shout us all drinks.?

[markimak]

haha ok.. so apparently im told that the r34 miss is still ther. i sealed them. the copper/metal tips are fine.. im yet to find the source of all the comotion..

[Pauly33GTS-t]

gapping is usually always the issue as you boost. 0.8 optimal gap.

Edited March 13, 2007 by Pauly33GTS-t

[Cubes]

I'd suggest to play with the gap.

Mine for example of 0.6 and 0.7mm idles like a fart. It feels slightly rough on idle.

0.8+ its baby smooth.

I have found for mysetup 0.9mm is fine for up to 15-16psi.

[Crash.]

Just to let you guys know about my issue, I was having a missfire on my R33, i went out and bought spitfire coil's and put them in, there was a little bit of a change but the miss fire was still there. Got new spark plugs, that didnt make any difference....

i took apart my AFM and cleaned that out, still nothing....

After talking to some people, the only last thing they suggested it could be was the Crank Angle Sensor, so found another skyline and removed it from that and put it on mine....It worked like a dream, went out and bought a 2nd hand one for $150 and fitted it on. Now i dont have any problems....

Hope this helps some people that can't figure out what is causing their missfire.

Edited March 19, 2007 by Crash.

[Cubes]

What sort of missfire did you have Crash?

A consistent high rpm pop or just every so often? Did it ever completely drop a cylinder then idle smooth back out after a few seconds after a high rpm rev?

[Rolls]

I have another theory to what could cause this misfire problem, on most skylines with increased boost (10-12psi on stock ECU) the ECU dumps a shitload of fuel in in the midrange (~5k) looking at any dyno chart will show this.

On my dyno chart it dips down to 10:1 however I have been informed that most wideband sensors can't read accurately below 10:1 so its probable its going all the way down to 9:1. This is rich enough to cause a rich misfire. It makes sense as the colder the weather the worse it happens, weak coils would just mean that the richest mixture they can ignite is raised hence new coils/taping them can fix it depending on the severity of the problem. I am getting my ECU remapped tomorrow and we shall see if this fixes my misfire problem. I purchased splitfire coils as well which helped the problem slightly however in cold weather it still misses, there probably are several causes to this issue however I believe this might be one of them.

Thoughts? Anyone in here have a remap/stand alone ECU and have misfire problems?

[Rolls]

Well misfire is completely gone after remap, turns out it was getting down to ~9:1 afrs hence the rich misfire.

[Crash.]

What sort of missfire did you have Crash?

A consistent high rpm pop or just every so often? Did it ever completely drop a cylinder then idle smooth back out after a few seconds after a high rpm rev?

When accelerating past about 1500RPM till about 4500RPM the car would missfire all the way inbetween, it was just a constant stutter, like the car was struggling....

When getting to high rev's it would just dissapear, the missfire was very noticable in 1st and 2nd gear....

Edited March 27, 2007 by Crash.

[Pauly33GTS-t]

reset your ecu, the ecu should relearn.