Missfire Boost@4500-5500 RPM - The Answer! (for me at least!)

[ABuSD]

Yeah my mates reckon it could b that (looks like mines already been changed) or a sticky valve.

If its your crank angle sensor will it rob u of power, and im talkin of a fair chunk here!!(guessing 50 or so rwkw)

[Abo Bob]

well i think so because it's now chirping at the top of 1st gear (tiptronic) and it never had the power to do that before.

[ABuSD]

sweet ill let yas know how i go!

Cheers

[Abo Bob]

Well rather than edit...

Changing the CAS just coincided with a few days of running fine. It was the coil packs after all. Now have some nice Splitfires in there.

[SLY33]

developed a pretty bad miss from 4grand up, well its more like a rev limiter sound after 4 grand! other than that it drives normal. Suspect its a coil or even 2 coils seeing as the miss is so bad. I was recently told that hitting the rev limiter frys the coils, i did not know this, and the car usually hits the limiter regularly...

after reading this thread i pulled out all the coils and had a look, the one closest to the firewall has a very fine crack as is the topic of the thread.

i took a picture but the crack is that fine, i had to struggle to identify it, but running my nail over it you can feel it. All other coils appear fine. you cant really see the crack in the pic, but the arrow shows where it is. it runs vertically about 3-4mm and starts underneath the raised numbers on the coil pack. Im still not 100% sure its a crack, as it looks like a mould/cast mark or something, but none of the others have it so i guess it is a crack....

im off to buy some insulating tape to wrap it up. Ill let you know if it fixes the prob!

[SLY33]

yeah the pic is crap, couldnt get the P.O.S. digi camera to focus close up..

[SLY33]

well i am stoked! wrapped the bastard up and she runs perfect! its amazing how such a TINY hairline crack can cause it to run so bad!

thanks nightman, if not for this thread i wouldnt have my car running so soon!

[Revhead]

Will have to give this a go - mine runs fine as long as I'm using less than around half throttle. Once over ~4k, if I use more than ½ throttle, it does the rev limiter-like miss. Still managed to drag off an XR8 with half throttle and 8psi though

[SLY33]

revhead that sounds exactly like mine... just keep in mind when your looking that the crack(s) are tiny!

let us know how it goes

[Revhead]

Will do, planning on having a look today (Sunday). I'll post up whether it fixes mine too - here's hoping

[benm]

Hrmm interesting thread. Last week (fri nite before the drags) I gave my car a squirt on 12psi just to make sure everything was running right (I never ever use 12psi, always 7psi for daily driving) and I was shocked when I got this miss/cut at 4,500-5,000rpm like mentioned in this thread.

At first I thought it may have been a fuel surge as I was getting low in fuel so I filled it up and still had the miss. Then I replaced the stock air filter with my K&N (it's dirty thats why it wasn't in the begin with) and still had the severe miss. So for the past week i've been meaning to check the spark plugs (haven't checked them in the past 47,000km however UAS regapped them to 0.8 about 3mths ago and said they were fine). I've had the plastic cover removed for about 3-4mths too just to let out heat quicker. Maybe I damaged the coils at my last track day a month ago.

I might put aside a few hours tomorrow to have a play around with this coil thingo if I have the right tools. I'm still not sure where/what to tape up tho? Is the tape to hold it together tigher or. . . ?

[R33vit]

Hrmm interesting thread. Last week (fri nite before the drags) I gave my car a squirt on 12psi just to make sure everything was running right (I never ever use 12psi, always 7psi for daily driving) and I was shocked when I got this miss/cut at 4,500-5,000rpm like mentioned in this thread.

At first I thought it may have been a fuel surge as I was getting low in fuel so I filled it up and still had the miss. Then I replaced the stock air filter with my K&N (it's dirty thats why it wasn't in the begin with) and still had the severe miss. So for the past week i've been meaning to check the spark plugs (haven't checked them in the past 47,000km however UAS regapped them to 0.8 about 3mths ago and said they were fine). I've had the plastic cover removed for about 3-4mths too just to let out heat quicker. Maybe I damaged the coils at my last track day a month ago.

I might put aside a few hours tomorrow to have a play around with this coil thingo if I have the right tools. I'm still not sure where/what to tape up tho? Is the tape to hold it together tigher or. . . ?

Ben if your not sure, bring it to my place and I will help you with it

[SLY33]

the tape just has to cover the crack, it doesnt have to hold it together as the crack wont be that bad, its just to insluate the coil pack as where the crack is the spark jumps out.

look at my picture on page one, where the arrow is, you just wrap the bottom half of the pack below the magnet/metal square part, to where the rubber boot goes on. I pulled off my boot, taped it, then squeezed the boot back on so the boot helps hold the tape. Dont wrap too many times like i did at first, as the coil pack didnt fit back in!

[SLY33]

btw you only need basic tools, some sockets etc, wrap the tape along the direction of the arrow on my picture, horizontally round the bottom half of the pack... assuming you find a crack that is! but it sounds like the problem... i thought it was my plugs too initially, but they were all still at a perfect 0.8 gap.

[Revhead]

Update on mine:

I found that every single one of my coils had that hairline crack. I taped up the coils, and the problem seems to have gone away, woohoo! Only problem I'm having is that the tape keeps falling off once I get a bit of heat into the engine, so I hit the coils with a bit of insulating gasket maker (the sensor safe stuff), then taped over that, then put the coils back into the cradle with a small amount of cotton fabric in an attempt to hold the tape in with a bit of force, rather than relying on the adhesive. Seems OK now, will have to give it an extended test today

[SLY33]

thats great that its fixed the problem, but the tape should really be seen as a stop gap measure until you can replace the coils! how about plastic welding?! the coil pack plastic is obviously very resistant to heat but i might just hit the crack with a soldering iron and see if it will melt the crack shut, talk about backyard techniques! But i have a couple of brand new coils on the way anyhow...

[Revhead]

Of course it's only a temporary fix, I'm not that dodgy I'd always planned on getting some Splitfires or something in there (investigated MSD but was going to cost ~$1.5k!!). It's misfiring again though, so I might rip em out (again...) and try to plastic weld them too. I just have to find something that won't blow the coils to pieces! I could always hit them with the oxy...

Nah just kidding, here's the plan though: I don't know whether the soldering iron I have will get hot enough, so I'll get an old screw driver, grind it down to a sharp point, wrap the handle in rags, and heat the fark out of the screwdriver with the oxy. That should make it hot enough to melt some plastic from an old distributor cap/coil/something that's lying around the workshop onto the end of the coils.

One other note with mine - the cracks had actually started to make their way up the bit that the spark plug sits in, making it really difficult to get a decent seal. If I get a chance/could be bothered I'll whip out the camera and try to get some shots.

[SLY33]

i was also thinking, would some silicone glass sealant work? It would be so easy to smear a layer over the crack, or even use it as glue to stick some other material over the crack.

would the spark jump through a layer of silicon?! if the soldering iron thing doesnt work, ill try the sealant.

does anyone know where you go to get propper plastic welding done? being so small and considering that appearance doesnt matter, i dont think it would cost much...

[|PRESA|]

I been running 10psi nicely for awhile now.. till a couple hours ago i put in an apexi pod filter and its the first time my machine is miss firing.

It started missing at just over 6,000revs then began to get worse, now misses at 4,500revs. This all happened in a matter of about half and hour of driving.

You guys really think its the coils? If so how much are a set of these Splitfire coils?

[GTST33]

Hi guys how much do new coil pack generally cost for R33s, and where is a good place to get them with not getting ripped off. Thanks