[plkettle]

Hi all,

Before anyone says it - i have done plenty of searches but have tried all of the stuff already...

I have an intermittent misfire when off boost between 2500 and 400 revs on light throttle.

I have checked the plugs (iridiums), cleaned the AFM's (nismo's), tried switching off the 02 feedback in the power fc, have splitfire coils, checked that no intercooler pipes are off, replace the ignition amplifier, checked injectors etc...

With the fault being intermittent it is proving hard to track down, it seems to clear out when you give it a blast but then returns after a while on light throttle at low revs (my tuner said that on the dyno the A/R looked fine)

Does anyone have any suggestions as to where to look from here ? any methods i can use to track down what is causing the fault ?


Any help is massively appreciated,

Pete

 

[SIHethers]

Pete

Sounds very much like the PFC glitch/intermittent misfire. Mine started doing it from the very first run after fitting the PFC. It's very intermittent on mine, like often doesn't happen, then can happen 2-3 times in a short journey. Always at mid rpm on light load, usually after a small increase in throttle. I've monitored everything when it happens and nothing registers untoward.

 

[plkettle]

it never used to do it though, had a power fc for ages and never had a problem before ? it is very similar to what you are describing but when it happens it misfires almost every time under those conditions until i give it some full boost and it seems to clear out for a while ?

Never misses a beat when on boost, and I dont like it when everything isnt running perfectly as i dont like driving it util i know the cause

 

[chaz_r33_gtr]

Try the earth fix that seemed to work for the Skyline Australia guys. Search this forum and you should find it. Basically get nice thick audio cable with gold plated spade terminals on there and bolt one end to the ignition amplifier ontop of the engine at the far back (ribbed metal thing with 4 screws holding in onto the engine) and the other direct to the battery (if R32) or to the negative terminal in the terminal block on an R33 or a suitable earth point.

Im gonna try this when i get time as my R33 seems to do it too ever since i had an apexi though not to the extreme yours seems to be

 

[pupsi]

Mine has started doing it since I had the poncams fitted, before that I had no problems, it only misfires when giving it some and then smoothes out.

 

[kennyc]

is it heat related Pete? Mine did it after I sat in traffic for a bit then tried to pull away it happened or at traffic lights

 

[chaz_r33_gtr]

I fitted a big fat earth lead from the ignition amplified to the chassis (using the factory MAP sensor bracket). Bought some 70Amp battery cable from maplin (£4/m) and some big gold plated spade termials (£3) and soldered the cable to the terminals and then fitted.

It hasnt missed like it used to do yet but only been on for a couple of days, however it does seem quite a bit smoother and has more immediacy when i press the throttle. Very strange i wasn't expecting anything other than stopping the 'Apexi hiccup'!. Anyone else done this mod asnd noticed the car being more spritely? I use iridum plugs and splitfires by the way

Cheers,
Chaz

 

[plkettle]

thanks for the help guys , i will try grounding everything better and see if it sorts it out

 

[tarmac terror]

Thought I'd resurrect this thread as I'm having the same bother and running out of ideas. Here is a list of things I have added/replaced recently:-

NEW NISMO AFM's
NEW Splitfire Coil Packs
NEW Trust Iridium Plugs (8's)
NEW GTROC Earthing Kit
NEW Ignitor (Ignition Amp)
NEW Coil Pack Wiring Loom
NEW 700cc Sard injectors
NEW NISMO Fuel Pump
Recent Remap by Abbey

Car running PFC on std turbos at 1bar.

Now, up until about 10 days ago the car was fine with the occasional PFC 'hiccup' (as discussed on another thread). Car would be quite rough and miss quite badly when cruising at 2800rpm(70mph), get better by 3000rpm(80mph) and be pretty much clear by 3200rpm.
Replaced the ignitor and coil loom today and took it out for a test to find its now missing REALLY badly and is having problems breaking through to higher rpms..say 1000-3500rpm whilst revving in the driveway. I've also checked all the boost pipes and they seem fine.

This is driving me MAD and looks like its going to have to go to a specialist as I cant think of anything else that it could be :chairshot :chairshot .

Any words of wisdom folks???

 

[tweenierob]

First thought would be to check you have no moisture around the plugs.
Second thought would be, did you replace the clips when the injectors were fitted? ive had 4 gtrs in in the last fortnight with missfires as the customers hadnt replaced the metal clips.

Rob

 

[tarmac terror]

Abbey fitted them but from memory there WAS one with no clip prior to me taking it to them. I shall have a look tomorrow.

Cheers Rob

TT

 

[tarmac terror]

Went out this morning and checked the injectors and all the other underbonnet wiring. Nothing amiss and all clips in place.
Started her up and it seems that the miss is there now at idle topen the throttle briskly and it pops and misses like crazy!!
I'm really all out of ideas...Its also got to the point where I reckon that I'm unable to DRIVE it to a specialist
BTW, how do you switch off the O2 sensor thing as described in the first post??

TT

 

[tarmac terror]

Well...went out yesterday and swapped the new ignitor for the old one; no change. Swapped the new coil loom for the old one; no change. Swapped the plugs with a spare set I had; good bit better but still missing slightly...

Checked vacuum and its reading what it always has.
Noticed that when it warmed up it was MUCH better. I'm thinking possibly water temp sensor???

Anyone else had one fail/start to go and what symptoms did it generate??

TT

 

[ExScoobyT]

The PFC `funny` a single defined event manifest as a single misfire, not a short period of `rough` running........

 

[MIKEGTR]

Check your plug gaps

 

[Adam Kindness]

plug gaps unless mega wide wouldnt cause it to run so badly on his drive way

 

[plkettle]

the cause for mine was an incorrect setting on the AFMS - i had changed the setting and when changed it back it somehow lost the nismo afm curve that had been programmed in.

1. check what AFM your powerfc is set to.
2. then go into the ETC menu, check the sensor readings and see what the lambda sensors are doing.

 

[tarmac terror]

The PFC `funny` a single defined event manifest as a single misfire, not a short period of `rough` running........

There are 2 separate events going on here......
Firstly the 'hiccup' as many refer to has been happeing since I bought the car and has still surfaced despite a remap.
The more serious issue of constant misfiring has only reared its head over the last few days. I am not suggesting that my current mishaps are linked to a PFC 'hiccup', in fact I've discounted the ECU being the problem. Maybe thats foolhardy as,TBH, theres not a lot left on the ignition/air/spark side of things that I havent checked already.


Strange though how it gets better as it heats up........??


TT

 

[zbloke]

You haven't got a broken wire or a bad connection at the resistor pack for the injectors have you?

 

[tarmac terror]

I shall have a look mate.
:thumbsup:

TT