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

Nightman

By Nightman,
in General Maintenance

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Nightman Explorer

Nightman

Posted
Posted

I *HAD* a miss in my R33 GTST when the air was cold out side or I put the boost up high. This happened at around 5000 RPM, after many months of chainging plugs, coils etc, I finally know what is wrong and a fix (not sure how long the fix lasts!)...

(the reason it does it more when the air is cold is the Boost was higher due to more dense air)

Note: All Coils tested FINE with a multi meter - This is not a valid test for this problem!

after a really really good examination of the coils it seems that there were lots of scorch marks and some other really small marks, which looked like the spark was jumping from the case of the coil!!! Looking VERY closely, I found that all bar 1 of my coils have a hairline (almost invisible) crack on the front of the coil! (I will post a decent picture later):

          ~~~

         --|  <--- Ignition Plug

  ~~~~~~~~~~

 ~~~~~~~~~~~~

 ~~~~~~~~~~~~ 

  ~~~~~~~~~~ <--- Crack Here! Top to Bottom and on Some, Into Plug Tube

  ~~~~~~~~~~

         ~~

         ~~ <--- Spark Plug Connection

         ~~

(Sorry about my Crappy ASCII Picture!)

What I did was tape the lower half of the coil.

          ~~~

         --|  <--- Ignition Plug

  ~~~~~~~~~~

 ~~~~~~~~~~~~

 ~~~~~~~~~~~~ 

  ~~~~~~~~~~ <--- Tape here

  ~~~~~~~~~~

         ~~

         ~~ <--- All the way to here

         ~~

I no-longer have a miss!!... I put the boost up even more then before, and still no miss!! - this morning was nice and cool outside on the way to work - still no miss!!!

Anyone having problems with missing, just tape the coils you already have, use a REALLY good Stretchy Electrical tape... not the 25c crap you can buy (this was useless!) - I will have to try and find some high temp non-conductive glue and try it some time too!

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SLY33
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

GTofuS-T
GTofuS-T

MrStabby just posted this video in a different post and thought it was very relevant to this thread. (Can't seem to embed it) http://youtu.be/Qirx_G4x5i0

Mitch_Dubya
Mitch_Dubya

Here's a pic of the coil that was arcing out on me. Running down the side and arcing to the head of the bolt.

Posted Images

tenzero Contributor

tenzero

Posted
Posted

Nice work in solving this problem mate. :)

I have a very similar problem and will try it out.

Was the electrical tape you used just pvc electrical tape? or the rubber tape from 3m that can be streched about 50% and is not sticky like normal tape??

Cheers.

D.

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Nightman Explorer

Nightman

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tenzero: PVC Tape, but a good brand one. - Theres just some really crappy tape that does not stick... and because the coil is tapered, its hard to make it stick...

sewid: Code tags made it better but still not 100% :)

When I find a Dig. Camera I will take some shots :) Waiting for the work camera to come back! ;)

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JimX Grand Master

JimX

Posted
Posted

Well it looks like you've already helped 2 people solve this problem. Does anyone know how they crack to begin with though? Is it just heat that stresses them out? Might be worthwhile setting up some sort of ventillation for the centre cover, especially in summer.

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Zahos Mentor

Zahos

Posted
Posted
How is a safc gonna fix faulty coils?

sure, it might mask the problem by changing the fuel ratio so as the spark is easier to make, but the problem will still be there and eventually get worse and catch up to ya! IMO Anyways...

Sorry, I guess you mis understood.

The problem with boosted R33's is that they run mega rich, and the ignition maps go all over the place, so you will definately get a misfire, or loss in power at the 5000rpm range with standard management. A SAFC corrects this problem. Once the A/F are laned out, the ignition maps start to look better, and you won't see this problem.

It looks like with cracked coils the problem is more evident. I dunno if my coils are cracked, but ever since the SAFC was installed, it has run like a dream. I'll have a look at my coils anyhow, coz the misfire I used to get was quite shocking....

Anyhow, good work on that discovery, but what I'm trying to say is that the problem goes much deeper than that... Some form of aftermarket management is definately needed on any modded R33!

Zahos

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Zahos Mentor

Zahos

Posted
Posted
Zahos: Ahh, yes.  If you boost up you can expect things like that (ECU goes into Safe mode - FILLER UP! :D)... But, I also *USED* to get a miss under normal boost in cold weather... Changing the Plug gap made it slightly better only!

Ahhhh -> "normal boost"

You're first post implied this, but coz I'm so used to hearing about misfire @ > stock boost, I guess I missed it....

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Cecam Enthusiast

Cecam

Posted
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The coils get pretty hot under that cover and probably overheat, for an R33 S2 just remove the cover, for series 1 I used one of the ignitor bolts into one of the cover bolt holes to keep that still, and same for R32's (remembering they have earth wires on the ignitor, R33's are down by the coil brackets). Appears to help some cars... sure it looks abit more ugly but the coils ain't frying anymore...

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ABuSD Veteran

ABuSD

Posted
Posted

Hey fellas i have an SAFC and i think i may have the same problem!!

And ive just had it tuned also :D (by a very respected tuner)

Thing is he tuned my car on a 27degree day and it gets worse when the weather gets colder!

Maybe its not a miss??

I also get a pop out of my zorst in between gear changes is that related??

Cheers

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Abo Bob Grand Master

Abo Bob

Posted
Posted

Just thought I'd let you all know. My issue turned out to be the Crank Angle Sensor.

I tried new plugs, then new coils (luckily had an identical car nearby that worked) but Crank Angle Sensor it turned out to be!

My car is an r34 GTT btw.

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