Intermittent Misfire?

[MAS_R33]

Hi guys.

Ive just got my car back from the shop where they installed a gcg high flow and did a tune.

The car runs amazing, with only one minor problem.

When under heavy boost it sometimes has a misfire (hard to explain, but feesl like a short loss of power. bit like a stutter.

This only happesn sometimes and usually when im in boosting hard in 3rd or 4th (around the 400rpm).

I guess it feels like a minor electrical problem (not that im qualified to know!)

I've done some reading but basically so many things to check I dont know where to start.

Anyone have any ideas before i take it back to shop?

thanks

[smithy85]

Which ECU? Apparently some PowerFC units have a software issue causing something similar.

[kitto]

How old are youe coil packs?

What type of plugs are you using @ what size gap?

If the shop tuned it, I would expwct them to put new plugs in.

I would be pointing to old coil lacks that are breaking down under boost

[MAS_R33]

sorry just realised i gave no info on mods!!

car is actually pretty stock.

Stock ECU

Stock Coil packs

Only mods are turbo back exhaust

pod

GCG turbo + boost that the guys could reliably tune to.

[MAS_R33]

I have a feeling you are probably right with coil packs?? I've never changed them since ive had car (5 Years)

Car made really good power considering the little mods (i couldnt believe the dyno sheet).

I had the plugs done a few years ago and used irridiums.

Say it is the coil packs (cos i dont know what else it could be!) is there any harm leaving it like this? Specially considering i rarely need to drive it that hard.

Thanks!!!!!

[Dajae]

Perhaps look at new coil packs? New plugs gapped to 0.8? Hows your coil pack loom looking?

In the DIY, Tutorials forum there is a stickied thread about misfire on an rb. Have a read, might find your answer in there?

[paulr33]

if it's a stock ecu what did they tune and how did they tune it?

[GH05T]

Wound boost up...have beer.... Finished

[DVS JEZ]

Lol thats about it.

Try a new set of bkr6es gapped at .8mm before spending 550 on splitfires

[GTSBoy]

Geez, if it's a stock ECU running a highflow then it could be clipping TTPmax.

[DVS JEZ]

Or it could be plugs, or other things, need to diagnose.

[MAS_R33]

thanks for the replies guys.

In terms of the tuning im not exactly sure. Basically my stock turbo let go so i got a GCG hi flow. The tuning was on the dyno to get it perform as best as it could without comprimising reliability.

It is my daily driver so I need to make sure it is reliable.

like i said I was surprised surprised to see the dyno sheet (225kw) and how amazing it runs.

most times the car is spot on and feels great. only occassionly when i drive it very hard (which i dont normally do, did it to see how the turbo felt) does it do it.

I have a feeling it is the plugs or coil packs.... not that id know.

If it is - considering that hte problem hardly ever happens could i be causing any problems be driving it like that?

thanks for your the replies!!

[paulr33]

yeah if its making that sort of power you will be hitting the standard ECU protection - TTPMax

what are you using to control boost, is it a controller or just the actuator spring?

if you are using a boost controller turn it to 2psi and see how it goes

if you arent using a boost controller then you are stuck with the minimum boost possible from the acutator spring, its probably 1 bar, which is prob too much for stock ecu

let us know answer to first question (controller or not)

have you got a fuel pump? this thing could be leaning out on boost if you haven't, mine leaned out on the stock turbo and 0.85kgcm2 and yours is highflow with more boost

[MAS_R33]

thanks for the replies again.

the boost controller is just the manual boost T, the cheap $30 ones.

not sure i get how the boost is working, well specifically why the minimum would be 1 bar? my standard turbo was set to 10psi. now with the hiflow the shop set it electronically to 11 (ok well on the dyno sheet that is where it is making the power). that said, my gauge can be pushed to 14.

Fuel pump is stock also.... my plan was to only upgrade things when and if the break. Hence the turbo.

Thanks again!

[bigjiz]

hey mate as old mate said a couple of replys ago i would start with new plugs bkr6es there $8.20 each at burson, I would say its missing due to the car making more power and ur shitty old plugs cant handle the load in 3rd and 4th and if you can i would replace the fuel pump asap cause the standard pump would only be good for a little over 200rwkw and im guessing its the original pump so it around 15yo and u dont want to lean ur motor out everytime u hit boost

[bigjiz]

O and i forgot u can pick up a bosch 029 fuel pump on ebay for around a $100 bucks now and they pump 255lt/hr which is more than enough for 225rwkw

[MAS_R33]

Hi guys,

thanks for the replies.

I'll look at plugs in the short term future.... well buying isn't a problem just that I dont't want to be changing them myself.

All advice appreciated.

[Dajae]

OP, what state are you located in? Im on my phone so cant see everything lol

[MAS_R33]

Im in Canberra.

[MAS_R33]

ok. I've popped the top of and got to the coil packs / plugs.

Changing plugs will be my next step - though wondering if there is any way to determine whether one of the coil packs is stuffed?

I thought runnign the car in the dark might have shown sparks if there was a crack. i may have been wrong but I definetly didn't see anything.

any help appreciated!