Ignition Misfire, Or Something Else?

[harks]

Hey guys,

about a month ago my GTR developed a bit of "hesitation" around the 3.2-3.8k rpm band. nowhere else in the rev range, pulled hard till redline, but when accelerating, would feel smooth while off boost, start to come on, feel like little stutters, then pull smoothly. i was perpelxed for a while and not overly concerned. Now its gotten a bit worse, and when accelerating beyond 4.5k it hesitates randomly throughout the rev range, when it hesitates in the higher rpm band it occassinally backfires mildly.

I plugged my laptop up and tried to have a look to see if anything was amiss and nothing looked wrong. So the only thing i can think of is if its misfiring, would explain the poor power and uncombusted fuel with the minor backfire.. would also explain the exhaust smoke. but im not by any means a mechanical guru!!!!!

I'm unsure what exactly to look for in the data log to prove this, or if it will. Im running splitfire coilpacks so dont reallly want to go and buy without a fair idea that this is the problem. Any thoughts would be handy.

cheers

Dan

[GTSBoy]

I'm unsure what exactly to look for in the data log to prove this, or if it will. Im running splitfire coilpacks so dont reallly want to go and buy without a fair idea that this is the problem. Any thoughts would be handy.

Just because they're Splitfires doesn't mean;

A) that they are clean, not covered in soot/grime causing them to arc over the outside of their housings,

B) that the coilpack look is not borked.

Take them out, inspect, clean, look at terminals in the loom, etc.

[breaker1845]

Do what GTSBoy said and have a look at changing your spark plugs or checking their gaping if you haven't done it recently.

There is a thread on here that links to a YouTube video on how to repair or fix misfire on coilpacks.

From what you have explained it seems that you get irregular arcing from one or many of your coilpacks causing a slight hesitation.

Unless the misfire is bad or it happens while logging you probably won't be able to find it.

I suggest looking for the YouTube video, just google "fixing misfire rb26dett coilpacks" or something. It covers in detail some tests you can do at home and the method to potentially fix your problem.

[harks]

Ahh okay, I'll have a look at it and see if i have time to inspect them tomorrow after work

[harks]

well, i watched the video, got the coilpacks out. tried to remove the first sparkplug.. it was so firmly in it snapped the metal crossbar on the tool before i could break it....

I figured well... i might aswell clean up the coils, dielectrical grease em etc.. all coils appear fine. put back together... same problem.

so possibly an actualy spark plug issue. they SHOULD be 15k old. any tips for getting em out if they are rock solid stuck?? plus, what is the likelyhood of it being a spark plug issue vs a coilpack issue? this may quickly become something ill need to wait untill i can get to melbourne to have good workshop look at

[GTSBoy]

You probably need to soak a bit of penetrene in down next to the plugs. Then you need a REALLY GOOD QUALITY sparkplug socket and bar and a careful technique so you don't snap the bloody thing off in the hole. An 18v cordless hammer drill might provide enough shock to rattle them loose whilst still being able to be held directly over the top and stave off the risk of breakage.

[dermy]

If the spark plug is ceased into the head it probably means its been there awhile and would be your issue

[breaker1845]

Be careful getting them out and make sure nothing breaks off down in there otherwise you might have bigger issues.

Best thing is to remove the plugs with correct tools and you'll probably notice their condition straight up.

Change them and see if you still get the problem.

[harks]

Thanks for the points.

I've never had misfire before, but it just started so so gradually, and progressively gotten worse, I would have thought a spark plug would be fine or broken, (although carbon build up or something I guess could be the issue of not gap it's) and a coil would have greater scope for deterioration..?

Wondering if I just bite the bullet, buy new coils and plugs, and a better tool and replace both next week after Easter weekend??

And anyone know where to get a quality plug remover tool in wagga??

[harks]

Quick update: I managed to get the plugs out today and cyl1 was quite lean, the others were all black.. I put a set of NGK BCPR6ES plugs in and an instant95% improvement!!!!

There is still a hint of hesitation at 3.2-3.4k rpm, which leads me to think a single coil is playing up, or an issue with the tune not getting properly modified when my poncams went it.

I'll put some photos up when I get a chance.

[breaker1845]

Poncams are drop in and don't require modification (no shimming or tune adjustment required).

Pull your coils out and bench test them if you haven't already and see if you can pick a suspect one.

[Piggaz]

Poncams are drop in and don't require modification (no shimming or tune adjustment required).

They're drop in which means you don't need to modify the head and can get away without a spring change. To not check clearances and not check the tune..... Well you're a bloody idiot.

[Blackkers]

Lean looking plug on cylinder 1 means you could have issues with that injector. Too lean will cause a miss

[harks]

Poncams are drop in and don't require modification (no shimming or tune adjustment required).

Yeah, despite them being drop in, i was of the undertsanding that anything modifying head performance effects the volumetric efficiency of the engine. So on a MAFless set-up which to my understanding during tuning with a wideband sensor calculates VE so that it can work without the MAF, would mean that the head is flowing a different amount of air to what it thinks it is if not correctly adjusted after installation, so despite the ECU "thinking" its at a 11.8 AFR at WOT, it may infact be 10.2 or something. Although i dont think a poor tune could make the car so rich it fouls the plugs within an hour and almost kills the car. especially since i have done about 1500km on the tune without an issue.

I had to go for a 200km drive back home today and by the end of the drive the missfire was incredible. SO, i'm back to purchasing an entire set of splitfires and replacing them on arrival. I suspect if i was to pull out the spark plugs they would be fouled again. so i'll need to give them a good clean when i replace the coils.

I just think that it may only be 1 or 2 that are bad.. but if 1 or two have gone, whose to say in 3k km another might go, atleast if i do them all i know they will be good to go. If the coils doesnt fix it(which i suspect it should), then it may end up being injector related. as you suggest Blackkers, but the missfire i suspect is an issue for more then 1 cylinder. But i have no way of checking that, and im not sure i trust any mechanics in wagga to diagnose the issue!

[harks]

Okay this is REALLY frustrating me!

I replaced coilpacks and pulld out the plus to inspect (performance has deteriorated to almost vonstant missfire regardless of boost or not) the plugs having only done 300 or so KM since change were horrible. See below

No 1. Cyl

No 2 and 3 (all others are exactly the same)

As you can see.. they are in bad shape, and the car drives very very poorly... I am now at a loss. there must be an issue with a sensor thats causing the issue.. any ideas?

cheers

Dan

[zebra]

. Although i dont think a poor tune could make the car so rich it fouls the plugs within an hour and almost kills the car. especially since i have done about 1500km on the tune without an issue.sue!

Seriously?

[harks]

Seriously?

Yes, because the car has done around 10,000km on the tune before any issues came up. Has done Bris to Melb and back in straight drives twice in the last 5 months.

[harks]

The tune was looked at by the workshop after the cams were installed.. but it had very limited dyno time and just had some minor ignition adjustments made.

still, it has done over 1500km since the poncams before any issues began.

[Ben C34]

Did you get it tunes with the poncams?

Cylinder one looks like its still a bit rich, the rest are mental rich. The fact they aren't all the same is concerning.

Comments like 'it must be a sensor causing the issues ' are going to make it hard you for you to figure out the issue.

Edit.

You posted when I was typing......

You mentioned only the timing changes with the cams tune, and you're running a map sensor?

That's your problem. Get it tuned properly .

[harks]

Comments like 'it must be a sensor causing the issues ' are going to make it hard you for you to figure out the issue.

True.

I didnt want to come across like i had my finger on exactly what it was, because i evidently have no idea what the issue is.

That's your problem. Get it tuned properly .

I made the previous comment becuase from my observations and limited mechanical knowlegde, it seemed illogical that one day the tune could start a problem after 1500km of perfect running (after the cam install), then after a temp fix make the problem after only a few dozen km.. if the tune is the broken variable it doesnt add up.

It will be getting looked at though.. my issue now is limp it to canberra or tow it to melbourne because wagga is lacking in tuners/performance workshops.. hence trying to explore alternatives that dont require flying in and out of wagga to get it sorted

again, thanks for your input guys, i do appreciate it.