Jump to content
SAU Community

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


Recommended Posts

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)

  • 1 month later...
  • 2 months later...

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!

  • Like 1

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 :D

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. . . ?

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

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!

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.

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 :)

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...

Of course it's only a temporary fix, I'm not that dodgy :D 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.

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...

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?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Latest Posts

    • Might also needs a stronger actuator with the right preloading. With older 2019 built bush G3 units, BB upgrade or 21U housing down size makes a pretty decent gain in response as well. 
    • Hey lads  so im finally putting together my rb30 forged bottom end and ran into an issue. I measured my main bearing clearance with arp main studs torqued to 60 ft-lbs using ACL H series STD size bearings and standard, un-ground crank shaft journals and got an oil clearance reading of about 1.3 thou measuring straight up and down and about 2.8 thou measuring at a 45 degree angle (just above and below the parting line). My machine shop said they measured the main tunnel and it was all within spec (they didnt say the actual measurement) and to go with a standard size bearing, which i have done and the clearance is too tight, I'm guessing because of the extra clamping force from the arp studs distorting the main tunnel. I was wanting to run about 2.5 thou main bearing clearance.  My questions are: 1. could i just use the HX extra 1 thou clearance ACL bearings? that would fix my straight up and down clearance making it about 2.3 thou, but then would the side to side clearance be too big at around 3.8 thou? 2. what actually is the recommended main bearing clearance for measuring near the parting line / side to side. i know its supposed to be bigger as the bearing has some eccentricity built into it but how much more clearance should there be compared to the straight up and down measurement? at the moment there is about 1.5thou difference, is that acceptable or should it be less? 3. If i took the engine block + girdle back to the machine shop and got them to line bore the main tunnel (like i told them to do the first time, but they said it didnt need it) what bearing size would i buy? the STD size bearing shells already slide in fairly easily with no real resistance, some even falling out if i tip the girdle up-side-down. If im taking material out of the main tunnel would i need a bearing with extra material on the back side to make up for it? this is probably confusing af to read so if something doesn't make sense let me know and ill try explaining in a different way. My machine shop doesn't come back from christmas break until mid January, hence why i'm asking these questions here. TIA for any help or info 
    • I bought the model back in Japan in Feb. I realised I could never build it, looked around for people who could build it, turns out there's some very skilled people out there that will make copies of 1:1 cars or near enough. I'm not really a photo guy... but people were dragging me in a group chat for the choice of bumper as someone else saw the car before it was finished as they are also a customer of that shop. I took the photo in the above post because I was pretty confident that the lip would work wonders for it. Here's some more in-progress and almost-done pics. It gives a good enough idea as to what the rear looks like!   I have also booked in a track day at the end of January. Lets all hope that is nothing but pure fun and games. If it's not pure fun and games, well, I've already got half an engine spare in the cupboard 
    • Well, do ya, punk? Seriously though, let's fu<king go! The colour and kit looks amazing on the car. Do you have any shots from the rear? I don't quite follow how the model came around. You bought the white kit and he modified it to match your car? Looks nuts either way!
    • So my car is finally back from paint! This took an absolutely insane amount of work and should get it's own build thread - but I didn't build it. It was completed by Troy @ https://scalekustoms.com.au/ I originally bought the AOSHIMA URAS Type R kit while I was in Japan, it's supposed to look like this when assembled: Now, I thought that was cool enough until I opened the box with Dismay, as there's no way I could possibly have completed it. The thing is 1/24 and has details down to the steering wheel horn button, which is a 2mm diameter sticker. I originally wondered if someone could make it at all, as is - But then things got a little carried away. It's worth noting that the model does not have an openable bonne, let alone engine bay, OR an openable boot. - Troy has worked wonders with 3D printer and presumably better eyes than I will ever have. My photos suck, so I will post up some of his in-progress ones he sent to me during the way. Unsuprisingly, he is very detailed. A lot of these are out of order. But he: 1) Made a LS engine and an engine bay appear out of thin air 2) Made the bonnet removable 3) Printed the rims I will buy in the future (or any rim you want) 4) Printed and added the wing that is going on 5) Tinted my back windows as this is what my car has IRL (privacy glass) 6) Added a licence plate. 7) Somehow did the interior 8) 3D Printed my actual seats 9) Made the exhaust under the car connect even though this is likely invisible. 10) Created a boot with my fking battery box, power steering reservoir, subwoofer and toolboxes back there. To say it's insane is an understatement. And I f**ked it all up because when I was re-mounting the wing (it broke in transit) I spilled glue everywhere and ripped paint up and Gregged the rear half of the car. Which about makes sense. Also, this arrived on the same day. Quite the change from: I spent 16 hours per day over the next 3 days pre-christmas putting the interior back together, mounting lip, fixing various bodykit problems with window mouldings, etc. and servicing, rebuilding my 370z brakes to go on the car 'soon', messing with heights to check clearances for new wheels, etc. I also had a foray into mounting wiper-mounted washer jets which was an absolute disaster. The bodyshop has welded (and painted) over the stock jet locations for reasons unknown to everybody (i.e they forgot) I also wanted to wire in the oil pressure sensor on Christmas Eve which was a BAD IDEA. You do not know terror like pulling your ECU apart, pinning in half-fitting pins that aren't the right ones, but trying anyway because it's Christmas eve, putting your ECU back together and having a no-start condition with a fuel pump not priming. Then you undo all your work and the fuel pump still doesn't prime. So after all that terror and horror and pain and tedious disassembly, the issue was the relay in the boot which seems to have died/stuck when I was turning the car off and on about 700 times testing shitty washer jets. I also re-wired the fuel pump power plug which fell apart in my hands. I am very happy I had 3 extra pre-made ones from a few posts/last Christmas's breakdown. https://bluewireautomotive.com/products/10-x-pcm-ecm-ecu-terminals I have put an order for these in, so I can actually add the pins to the ECU properly. The commodore ECU does not have the pins for Oil Pressure via ODB2. However the ECU can support it if you create the pins and wire them in. So for round two, and somehow attempting to route that into the engine bay through my impossible engine bay grommet is a fight for another day. It's 40C in Melbourne tomorrow, I am half tempted to drive the car with the aircon on to deliver presents to my partner's family and see if it helps with the overheating-on-40C-days-in-traffic-with-aircon-on-only issue that the vents were intended to solve. Do I feel lucky?
×
×
  • Create New...