Mysteries Misfire (r32 Gtr)

[itbmils]

OK guys

I surrender - I've had a VERY intermittent misfire in my R32 GTR for a while now - and I need some suggestions on what to look at next.

I have had a full engine rebuild, not to fix the misfire , but I did have it before the engine rebuild. Since then I have changed

ECU - now have a PFC installed and tuned

New iridium plugs

New splitfire coil packs

New SX fuel reg

New Fuel filter

New Tomei fuel pump

New Tomei timing belt

New pullies and tensioners

New Tomei Adj CAM gears

(New bloody everything)

The injectors have also been cleaned and flowed

I get the misfire once every 20-30 mins of driving - so not very often - but when it comes, it s big one. I get a big miss (feels like I've hit a pot hole) and I get a small back fire thu the engine (not the exhaust). It seems to be more dramatic when cold – but I still have the problem when hot. It can happen even under low load and/or full boost too.

No, my tuner does not know what it is either – but they are more than happy to charge me $70/hr (plus a shopping list of parts) to find it.

Could the igniter cause this, what about the coil pack wiring loom, battery, alternator (ARRRGGG!!) ?

If I get hold of someone with the PFC software – will that help to track things down. I could buy it myself, and run the car around attached to my laptop until I capture something ?

talk to me - this does not seem to impact performance - but it's FARKING annoying

[BookyVL]

What havent you changed then? If it is that intermittent, doesnt sound like wiring but still could be...

Does this happen when driving in a straight line, cornering?

[itbmils]

What havent you changed then? If it is that intermittent, doesnt sound like wiring but still could be...

Does this happen when driving in a straight line, cornering?

<{POST_SNAPBACK}>

OK - the things I have suggested are about the ONLY things I have not changed yet

battery

plug leads

igniter pack

alternator

is there anything else in the ignition chain that I have missed (I'm not a mechanic or auto electrician, so there must be) ?

It can happen any time - straight line usually now that I think of it - could a dodgy battery connection do this ?

I installed a 'grounding kit' a while back - and the -ve battery terminal is a little over sized for my battery - but still tightens up OK (I'm grasping at straws now !!!)

So - would the PFC software capture this sort of electrical fault ?

[Amaru]

Is it just a single miss every so often that makes the car jump a bit or does it constantly miss for a few hundred rpm through the rev range?

If its just a single miss, you will be happy to know my car does it A friends car was fine as well, he put a power fc in and it also does the same thing now. As for what it is, no idea. I have had the car tuned by multiple places and no-one can get rid of it. Two of the places have also said its a problem in the specific revision software power fc I have and its not fixable.

If you find a solution, let us know

[itbmils]

Oh VERY helpful

I'll get to the bottom of this some how - and will let you know

what version of the PFC software do you run ?

my tuner wants me to insall the new HKS CDDI system next !!

[Taran]

Try changing the leads

[BookyVL]

Yeah, i agree, try the leads first..

Also could try cleaning the plugs again, even though you have just changed them...

Where are the coils located? Are they like the standard coils on top of the plugs?

[itbmils]

Yep – the splitfires are a direct swap for the old coil packs (which are obviously fine BTW)

where would I get new leads - I'm thinking of the words

Nissan and wounded bull - right

Can I get a set made up ?

[Taran]

I think you can get splitfire ones but i'm not sure how good they are.

[ylwgtr2]

as far as i was aware gtr's dont have leads....or are we talking about the rubber boot?

[blur]

could be an air flow meter loosing a signal for a split second, or the wiring plugs to them a bit dicky?? that could do it, have they been swapped??

[itbmils]

could be an air flow meter loosing a signal for a split second, or the wiring plugs to them a bit dicky?? that could do it, have they been swapped??

<{POST_SNAPBACK}>

Well my GTR has leads - not high tension leads tho - more of a loom really. They run from the igniter to the coil packs. Mine look old and perished – and I would like to replace both the loom and the igniter – but I bet it's cheaper to buy the HKS CDI (Twin Power) – which is about $600AU delivered from Nengun.

No - I have not changed the AFMs - yet

I do have a pair of Series II RB25 AFMs to fit up- but I need the bigger suction kit (and a full retune) to do that - they are on the list

I will check / clean the connections tho – and let you know

[r33_racer]

what the hell are leads? Correct me here, but dont oldschool cars with dizzys and coils have leads to link em up to spark plugs right?

Coil packs which are in skylines sit right ontop of the sparkplug with no intermediate lead connecting the two. Unless you mean the plugs?

[itbmils]

what the hell are leads?  Correct me here, but dont oldschool cars with dizzys and coils have leads to link em up to spark plugs right?

Coil packs which are in skylines sit right ontop of the sparkplug with no intermediate lead connecting the two.  Unless you mean the plugs?

<{POST_SNAPBACK}>

the coil pack still needs to be connected to the ECU and a power source - right ?

so as I said - it's not a high tension 'lead' - but they do have a wiring loom that connects the coil to the rest of the ignition system

the coil packs take the place of a single shared coil in a typical car - which means the electric charge actually builds at the coil pack (stronger and faster than a single coil). But even a normal coil is connected to the battery somehow

trust me dude - I have leads that come off the coil packs

HtH

[saliya]

Hey,

if you have PFC and a dodgy AFM, you _might_ be lucky enough to see it on

the section that shows the sensor outputs. Have someone monitor the hand

controller, and see whether there is an AFM voltage out of whack (they should

be fairly similar, and I think always above 1V) when you have the miss.

Regards,

Saliya

[ylwgtr2]

your talking about the wiring loom then.....a simple check with a volt meter for continuity will be enough to decide...if its a closed circuit from one end of the wire to the other then there is no need to replace it.....igniter modules are a week point on that model.....i would be sniffing around that

[itbmils]

Hey,

if you have PFC and a dodgy AFM, you _might_ be lucky enough to see it on

the section that shows the sensor outputs. Have someone monitor the hand

controller, and  see whether there is an AFM voltage out of whack (they should

be fairly similar, and I think always above 1V) when you have the miss.

Regards,

Saliya

<{POST_SNAPBACK}>

OK - didi some monitoring - and the AFM reading clearly takes a dip when I geta misfire - but does that mean it's the AFMs

I mean - if I've had a miss for some other reason - that would imapct air flow - right ?

[itbmils]

your talking about the wiring loom then.....a simple check with a volt meter for continuity will be enough to decide...if its a closed circuit from one end of the wire to the other then there is no need to replace it.....igniter modules are a week point on that model.....i would be sniffing around that

<{POST_SNAPBACK}>

Yep - I've done that - problem is - it's very intermittent

I'm not sure this type of test would actually capture a dead short - as it only seems to happen from time to time

the wires are very old (brittle) but they still seem to conduct OK to me. The plugs seem OK too (also old)

I'd like to replace the leads and the ignitor – but I'm not sure where to get them from

[saliya]

OK - didi some monitoring - and the AFM reading clearly takes a dip when I geta misfire - but does that mean it's the AFMs

I mean - if I've had a miss for some other reason - that would imapct air flow - right ?

<{POST_SNAPBACK}>

Hey,

Sorry, I don't think I've made myself clear Yes, when you have a miss, your airflow will

go down (I don't know exactly by how much, because my car doesn't do that). But I _did_

have a faulty AFM, the behaviour on-car was much like a very intermittent miss.

If the AFM is giving faulty readings for enough of the time to alert the PFC, the PFC will light

the exhaust temp light (disconnect an AFM and start the car, you'll see what I mean).

But my one would only read badly occasionally, looked like a dodgy contact inside

the AFM itself - not long enough to light the light but long enough to have the engine hesitate.

If it's a faulty AFM, that particular AFM might have a reading that's out of whack (with the other one).

Say one AFM is reading 2.5V, but the other one is reading 1.1V, check the lower voltage one.

Or if at any time either AFM reading is below 1V, that is abnormal. In my case, when I had

the fault the person monitoring the controller could see that the voltage of that particular

AFM went down to nearly 0V. But it would only do it for a fraction of a second - hence, why

you will need to be lucky

Regards,

Saliya

[WazR32GTSt]

well i'm not an expert on mechanics or electrics, but i can only put in the following in hope that it might help

seeing as you have spent so much on an engine rebuild and obviously want it to run perfectly.. have you considered buying an entire new wiring loom and replacing your old, worn, broken wires with the new loom? who knows where you might have a broken wire that may be coming loose intermittently..

anyway good luck

Warren.