Intermittent Shuddering / Misfire

[butcher]

Been scouring this forum for days now (I'm a long time occasional lurker), as I've been trying to track down the route of this problem. And I'm struggling, so I thought I'd just sign in and ask for your advice.

The Symptoms

Over the past week the car has started misfiring / shuddering. The problem comes and goes at the drop of a hat. And it seems to becoming more regular.

At idle, the car may be running fine. Smooth as ever. Then suddenly it'll drop maybe 100 revs, down to 600rpm rather than 700rpm. The rev counter will sit perfectly still at those revs, but there'll be a pronounced shudder in the car and burbling through the exhaust like it's not firing on all cylinders. It feels very much like sitting in an old diesel van.

When you pull away, it becomes even more pronounced and sounds like what I've read on here, an old WRX. I couldn't put my finger on that though as I've never been in a WRX. I could even go one step further and say it sounds like an old american V8 muscle car! Except without the power

Then instantly, it's gone, power shoots up like the turbo's just kicked in (not the case, I can hear it spooling when it's running rough) and the engine's totally smooth again.

This problem comes and goes purely at random. No better or no worse at any rev range (though it's being driven easy a. because I don't want to break it, b. because the weather doesn't allow otherwise here at the moment).

ECU

Checked for fault codes on the ECU. Two slow flashes, followed by one quick flash. Which I'm led to believe is the ignition signal.

The Car

Pretty much totally standard RB25DET series 1 Stagea, with the exception of Yellow Jacket Coil Packs, NGK Iridium Plugs (both less than a year old), K&N panel filter and 3" exhaust.

So Far..

From what I've been reading, the symptoms pointed to the AFM. I've had that out today and re-soldered the pins. This made no difference at all. I'm yet to try contact cleaner on it. I haven't done anything to the car recently. Later checked the error codes and got 21, ignition signal (I believe? Though 12 is the AFM..! Am I reading these right?).

This is my daily driver and need it to get to work, so would appreciate any help.

Thanks

Edited December 11, 2010 by butcher

[JOHNNNY]

sounds like you might have a coil pack on the way out mate , they can start out as an intermittent problem then go all of a sudden .

also check that it is all nice and clean in the vally were the coil packs sit as somtimes dirt or water can cause the coil packs not to contact correctly .

i dont think it is a AFM problem as usualy it is not an intermittant problem , it will idle fine but as soon as you load or rev the engine it will stall .

cheers johnny..

[rd-runr]

I believe i have the same problem but have not found a solution yet.

I have swapped out the AFM and fuel pump with no affect.

Was thinking coil packs as the problem but not fully convinced yet.

[butcher]

Thanks guys. I've been on the case today, and it looks like one of my yellow jackets may be failing. 

Fortunately I still have the originals, and  swapped the, at least what I hope to be, offending item over. 

Bit annoying if it is when they're only a year old. 

[butcher]

I believe i have the same problem but have not found a solution yet.

I have swapped out the AFM and fuel pump with no affect.

Was thinking coil packs as the problem but not fully convinced yet.

Don't know if you've came across this before, but I've had the Stagea over a year now and although I knew you could read the error codes from the ecu, I didn't realise you could do it so easily, until I found this guide the other day http://www.skylinesaustralia.com/forums/topic/266512-reading-nissan-fault-codes-ecu-fault-codes-how-read-them/page__p__5488045__hl__ecu+error+codes__fromsearch__1#entry5488045

Takes no more than 10 seconds to do. 

Code 21 is the ignition signal, and if you get that, then there's a good chance it's the coil packs. It had my mind blown though, as the AFM is code 12, and whilst everyone states that the long flashes are the first digit, the R33 engine manual states otherwise! After talking to people, with them testing it with consult software and from my own experiences today, I'm pretty sure the R33 manual is wrong. Or at least the english translation. That or I'm reading it wrong!

Anyway, over the past few days I've heard quite a few stories about aftermarket coilpacks packing up, in a very different and more abrupt way than the OEM ones. I've heard a lot of people say the coil packs won't trigger an error from the ecu, which I can believe from the OEM units, as they still fire as normal. It's just that the spark gets directed to the wrong location. So maybe aftermarket units are simply prone to good old electrical failure...in which case there's no reason the ecu wouldn't pick that up.  

 

[-RBD2-]

Before you go buying new packs check all (and I mean all) of your incooler joiner pipes

wen I bought my c34 laurel (s2 rb25det) it was throwing out code 21 (ignition signal)

after changing plugs,taping coilpacks,changing afm,new fuel filter and 4 hours on a dyno

turns out the intercooler joiner that goes thro the guard under the pod was split on the bottom section ofthe 90degree bend

was the stupidest little thing to fix and once my tuner found the drama it took a total of 10mins to fix

shame it had already been on the dyno for 3 and a bit hours...

What it was doing was taking the airflow reading and adjust fuel as per normal,but once the split pipe opened up again it was getting all sorts of bad air/mixtures and cutting power to the injectors.if we kept our foot in it it would eventually break thro the shudder and almost rev out as per normal

was also boost spiking like a motherf**ker,dyno sheet is a mess!

Just my thoughts,hope you get it sorted.I know I was so frustrated after ownig my laurel for 1 days before this shit started

nearly gave up a few times!

Good luck mate

[butcher]

Before you go buying new packs check all (and I mean all) of your incooler joiner pipes

wen I bought my c34 laurel (s2 rb25det) it was throwing out code 21 (ignition signal)

after changing plugs,taping coilpacks,changing afm,new fuel filter and 4 hours on a dyno

turns out the intercooler joiner that goes thro the guard under the pod was split on the bottom section ofthe 90degree bend

was the stupidest little thing to fix and once my tuner found the drama it took a total of 10mins to fix

shame it had already been on the dyno for 3 and a bit hours...

What it was doing was taking the airflow reading and adjust fuel as per normal,but once the split pipe opened up again it was getting all sorts of bad air/mixtures and cutting power to the injectors.if we kept our foot in it it would eventually break thro the shudder and almost rev out as per normal

was also boost spiking like a motherf**ker,dyno sheet is a mess!

Just my thoughts,hope you get it sorted.I know I was so frustrated after ownig my laurel for 1 days before this shit started

nearly gave up a few times!

Good luck mate

Cheers Rb. I've no intention of buying new coilpacks just yet. I've two sets there and pretty sure I can find some fully functional ones out of the 12!  Will do me for a while anyway. 

I did initially think there was maybe a leak somewhere, but I'm hoping it's sorted now. It's interesting that it could trigger fault 21 though..

[-RBD2-]

Yeah I know dude,wen it was at my tuners there was 3 of us working on it and we changed ecu,coilpacks,afm,put stock boost solonoid back in

all a waste of time!

Was a last ditch effort to triple check all the intercooler joins,and that's what fixed it

good luck with it buddy