Mysterious Misfire :s

[aphid]

Hey all,

First things first.. Engine is an rb25/30 with an externally gated garrette t04e, power fc and the other usual mods running a wasted spark setup that I finished installing on sunday. Car was running fine before the wasted spark, and was running perfectly fine after the wasted spark for about a day.

I first noticed the misfire after boosting out of a corner and had the usual low fuel misfire, so I went and put in 5 litres of mobil regular premium to get me to a decent fuel station.

Pulling out of mobil the car was running fine again till about 5 minutes down the road where I again boosted at which point the engine completly cut out, it was as if somebody had unplugged the igniter pack, 100% misfire.

I pulled over to the side of the road and tried to start my car but it wouldn't. I left it 5 minutes and tried a few more times, the last of which she turned over perfectly, not struggling to start at all. I thought this weird and decided to turn home to stop myself getting stranded and found that as soon as I touched the accelerator the car would misfire, much the same as a set of dodgy coil packs. By the time I got home I could only let the car idle in 2nd gear as as soon as I touched the accelerator she would misfire and almost stall.

At first I checked the usual things, ignition is fine when the misfiring occurs as is the timing.. Car didn't seem to be blowing any black smoke during the misfire indicating perhaps she was running lean. At this point I'd also like to point out that at no point was the car knocking on the drive home (power fc with fc datalogit hooked upto the laptop datalogging so I started to suspect that it may be a dodgy fuel pump, so I swapped it out with a brand new 040 I had laying around, however the problem persisted.

It does seem weird that the problem started after installing the new wasted spark setup (3xchampion bomb0d0re coils with stock r33 igniter), but the car did run fine for a period after installing them

I've now checked all sensors and they all appear to be reading fine, and I'm at a loss for what else to do.. any thoughts or idea's would be greatly appreciated

cheers,

marcus

[FLY12N]

Nasty!

I'd be double checking everything.

Good luck with it.

[WYTSKY]

jeeze, does not sound good mate.

I know this is a long shot, but for a time I had a miss firing problem too, which was not as severe as your case, but at some points it got close. I bought all new sparks, splitfire coils, etc etc.. I was almost going to buy a new harness to plug into the coils.. but Nissan wanted over 300 for that!

turned out, it was very simply... a small rubber hose that had a considerable crack in it at the bottom of it... changed it over for 8 dollars and my problem was solved!

as I said, I know its a long shot, but you sound as though you have exhausted most other options.

Good luck with it mate!

Adam

[Guilt-Toy]

so where is this rubber hose mmmmm ???? care to tell??

[700HP-GTR33]

You may have cooked your spark plugs...get them out and have a look.

Low fuel...hot burn...wasted spark plug.

Alternatively check your fuel regulator and filter.

Good luck.

[Strik3r]

this may also sound stupid, but it *could* be your AFM playing up.... What did datalogit say about AFM voltage at the times ? If your seeing really large spikes when you touch the throttle, could be AFM being stupid and causing the car to dump a tonne of fuel and subsequently missfire/die. Also check TPS & CAS ??

[aphid]

thanks for the replies guys

yeah i'll swap out the plugs tomorrow for some spares i've got laying around, else i think i'm going to grab the stock coil pack loom off a mates wrecked 33 (i butcherd mine making the wasted spark ) and whack the stock ignition setup back in there.. just seems too suss that this problem would arise a day after changing to the wasted spark.. must've triggered something somehow.. will also check the afm voltages again, but i didn't see any rich smoke coming out of the exhaust anyway keep the idea's coming, thanks heaps guys

[datsqik]

check all your earths.

[RB26GTST]

check all your earths.

put in some decent quality fuel. I had a miss firing problem just the other day - it was bad fuel.

New fuel = no worries!

[DECIM8]

I know it might be a strange suggestion but did you check your fuel pump? was it priming when you had been trying to turn it over? could also be this if its not the fuel, perhaps carry around some fuel cleaner from now on?

Reason i mention fuel, it could have cut fuel giving simlar feel to misfire jerking and since it actually stopped its going to be either of the two. Just throwing it out to you.

Edited April 19, 2008 by DECIM8