Misfire Not Coils... Spark Plugs Maybe?

[bombtrack]

I created a little post a while ago as well as doing a fair bit of research on the forum because my R34 GTT was missing, running like shit on and off... sounding like a wrx.

Anyway today I finally got around to chucking some splitfire coils in and long story short it's still doing it. On a positive note, the throttle response seems to have improved considerably.

Any tips on what's next for me to check/replace? Could I have done something wrong with the coil install? Seemed pretty plug and play to me. Could the sparks be fouled since I have been driving with this problem for a while? Could it be my O2 sensor? I have one to install, I just can't get under the car to install it. I also have a Z32 AFM and new injectors to install, which I will get my tuner to install so he can tune the PFC to suit at the same time. Anything else?

Any help would be greatly appreciated. Cheers.

[godzl1975]

could be n injector

[stolen_s15]

Throw in some new plugs mate, see if thats the problem. Otherwise as above check your injectors.

[bombtrack]

Would resetting the PowerFC have any effect?

[Sandeep]

Have you isolated which cylinder is the suspect? Turn your car on and starting from the front, disconnect the plug to the coilpack. The rpm should drop when you disconnect the coilpack connector. If the rpm doesn't drop then that means that cylinder(s) is the one you should look at closer. Do this for all 6 cylinders and try to make a note of which cylinder causes no rpm drop or a very small rpm drop.

check the sparkplugs and also while your doing the spark plug change, get a compression test done. I'm not sure what the compression figures should be for your car but the figures should be consistent accross all 6 (ie you don't want 150, 155, 160, 110, 155, 160)

[bombtrack]

Yeah this is actually pretty strange.

Prior to changing my coils... the car would occasionally run fine(i.e. run on 6 cylinders), occasionally it felt like it was running on 5 cylinders, sometimes felt like less... or that is what I interpreted the different feels to, if that makes sense.

Now that I have changed the coils, pulling the breather pipe, blow off valve, etc. off the car to get to the coils, then re-installing it all, the problem feels different and it is constant. It almost feels like I have a leak in my exhaust manifold (I only know what this sounds/feels like due to breaking a stud on my old VL Comm and then driving it down to the exhaust shop - bap bap bap bap).

Could installing the breather pipe or blow off valve incorrectly(showhow >.<) cause a lumpy wrx-like idle and shitful performance? Would a leak in the BOV connection cause something like this? I might get some gasket goo on the weekend and make sure I have a tight seal.

Cheers again.

[boostin_r33]

Had your 34 been sitting there for a while not being started? sounds like what happen to me only coz i hadnt started it for a week or so turned out there was just shit fuel!

[R334door(s2)]

have you gapped your plugs or got your mechanic to do it.?

what are they gapped at.?

i suggest 0.8 gap.

[Jmaac]

Have you put new sparkplugs in since?

Were they gapped already at 0.8mm to help with your old coilpacks?

[missusR34GT]

Hey

Sounds like a similar problem I had not too long ago.. at first we changed the sparkplugs.. bought iridium sparkplugs.. but it was still misfiring...

Then changed coils also to splitfires.. still misfiring.. kind of like a murmur in the engine..

Then had another mate look at it.. it turned out to be coolant.. it had spilled on one of the coils because when we put the splitfires in we took the cover off (a mate said that was ok).. but we should have kept the cover on for that reason.. so yeah just cleaned the coil with a paper towel and put it back in.. after that.. my car was sweet!

Hope that helps

[bombtrack]

An update: for you guys helping me out:

Coils changed but misfire persisted. In fact changed from an intermittant misfire to a constant misfire.

Changed sparkplugs - and gapped them to 0.8mm (the ones I pull out looked to be gapped to 0.1mm!!) - no improvement.

The coil cover has gone back on after each piece of work was completed. Unlikely the coils have been fouled in any way.

Possibilities:

The current tune is for spark plugs gapped at crazily small gaps (~0.1mm)?

I got some dirt/something in my cylinders when changing the spark plugs?

I might try regapping my plugs down to 0.1/0.2 but failing that I'm leaving it to the experts. I have a bunch of parts being installed by CREATD including a 2835 pro s turbo kit and cams so I will let Rob fix it!

[bubba]

Could be the plugs onto the coils, I know my car is a fair bit older but the insides of the coil plugs were falling apart causing a real nasty misfire when it got hot. Soldered on some new plugs off a mates' loom and it's all fine now, been meaning to get myself a new loom eventually.

[rych]

if all else fails, pls check on your intercooler pipping and oh might sound really stupid, but have you been using lower grade petrol? i know some gas station in my country sell mixed graded petrol.

[bombtrack]

98RON only mate, that what it's tuned for I use the same petrol station when I can as well as they have fuel that was proven to be good prior to the misfire issue and in my old R33.

[gts4diehard]

fuel and sparkplugs are the usual candidates.

IS the bad running all on the same tank of fuel? never discount the fuel especially when there is a shortage of the higher octane stuff around at the moment, who knows what the gas stations with premium really have in their tanks! maybe some octane booster or injector cleaner may help out here, fairly cheap and easy to do.

On the older skylines with original coils a common fix (as mentioned above) for misfires was to gap the plugs to 0.8 instead of 1.1 to make it easier for the 'old' coilpacks to generate the spark, however since you have new coils (assuming the other electrics are ok) then you should be able to run the std plug gap. copper plugs are fine to run in these engines, you don't need to go to the expense of platinums as the plugs are fairly easy to get at.

another cause could be the signal that the coils are getting to fire the plugs - maybe a crank angle sensor issue. fairly unlikely as the car is still not too old, more likely to be a plug or fuel issue.

The car isn't running any high boost numbers is it? it may need a different grade of plug if it is.

Edited April 26, 2008 by gts4diehard

[bombtrack]

Pretty sure the fuel is ok, although some octane booster might be a good idea. It does run the same though from tank to tank. Injector cleaner is also a good idea. I have new injectors going in shortly...might also fix the problem. I'd do it myself but I am not 100% on tuning the PFC myself.

Coils as you say are new... and the plugs are gapped to 0.8. i am not clear on whether the fact that the old plugs were gapped so small(0.1mm) and the new plugs are gapped to (0.8mm) as per advice from this board and numerous other people could make a difference given that th eold tune was done with the smaller gap but that doesnt seem very logical to me, it's just a matter of me pulling it all apart again and gapping the plugs back down to (0.1/0.2) to test.

I hope its not CAS or something more sinister.

The car is running ~12psi but I run plats normally so I doubt its a plug grade issue. I have some coppers in there atm while I am testing for all these issues. I am getting cams/turbo/injectors/fuel pump installed soon and have been assured that the car wil leave the workshop sans miss so if I dont fix it myself soon, I trust all will be well as soon as I can afford the install/tune.

My biggest worry now is I hope I am not doing any damage driving the car around while its running this way. I generally dont take it above 3k rpm and I dont drive too far but i do need it to get to work.

[AdamsFast1]

try a compression test and see if you may have a valve stuck open. also any history of head gasket blown? does your exhaust smell sweet? often a simple indicator that there is coolant getting into the cylinder.

[bombtrack]

No history of head gasket blown but I will get comp test done anyway. Comp test of 18months ago came up fine thats before the problem arose though.

Exhaust smells rich, don't think it's sweet. No real evidence of coolant in the cylinders. Coolant in the radiator looks normal also, no milkiness/oiliness.

Cheers mate.

[bombtrack]

Final update for the guys who were helping/interested:

Took it down to Creatd and after some initial worries about the motor they changed the coil loom and problem solved.

Apparently there were some other unrelated issues as well but the misfire is gone and the turbo's installed. Injectors/brakes/cams/cam gear going in shortly. Should get it back Monday with quite a few extra horses and some better anchors! Can't wait

Thanks everyone.

[Tomek]

Congrats man...

Having the same problem too .. back firing when building boost, changed the spark plugs snapped 2 screws on 2 separate coils .... took her for drive, firing worse then before..

Im 90% sure it's the snapped screws causing the problem.. lol.. I hope so

Anyways. have fun with the car on Monday!