Jump to content
SAU Community

R33 gtst Slight missfire on idle... Spark plug gap suspect


Recommended Posts

Hey guys, ive done some reading up on this but want to get other peoples opinions on changing spark plug gap and whether it will affect my tune. So far i've checked coil packs and replaced with brand new splitfires, new ignition module a few years ago, new fuel pump and injectors, New z32 afm, all vaccum hoses replaced as well as headgasket and intake and exhaust manifold gaskets with genuine nissan items. Tps and aac valve are both relatively new as well. Car is tuned on e85 running a power fc. Made 408rwhp on stock motor and pulls hard with no missfires or hesitation. The only time it does miss is on idle and seems to splutter a bit under 2500rpm. Its only a very slight miss like a cylinder dropping sound but is more noticeable when warmed up. Im running ngk bcpr7es plugs gapped at 0.8 but was wanting to see if 0.9 gap would iron out any idle miss im having and not massively affect my tune. Cheers guys

^^^ as per GTSBoy says, That gap is only needed when you're boosting.  At idle or just above, it won't matter.  Generally at idle you could have just about any gap in the 1.2 to 0.8mm range and it wouldn't matter.

See if it still happens with your A/C turned off.

Cheers for the input so far guys. So with the a/c switched on there is literally no miss! It idles at 1000rpm but the miss comes back when its switched off. Once the car is at operating temp it idles at around 850-880rpm. I also noticed when i unplug the o2 sensor the miss goes away completely but the afr's drop to around 13 on idle instead of sitting on around 14.7 which i imagine is normal as it was tuned with the o2 sensor. Does this mean theres an issue with my o2 sensor or possibly the wiring?



Missfire on idle? That's just called 'having any RB engine'


Thats what the tuner said too lol he couldnt pick up any faults with anything but surely it cant be normal. It sounds shit on idle! Slight miss every few seconds rather than idling super smooth like it did before. Oh well i might just have to live with it then
O2 sensors get old and slow.  The heaters also stop working and they don't then work when cold (ie at idle).
O2 sensor was also replaced not too long ago with a genuine nissan sensor as previous one was getting on.

Just an update guys...had a mate of mine double check the gap on my plugs and turns out it was only around 0.5mm! Pretty pissed off as a reputable tuner gapped them for me too! Anyway they're now gapped to 0.8mm and no more miss what so ever and the car obviously feels smoother too. So...yes, spark plug gap can affect a cars idle lol

I wouldn't call someone that doesn't know the difference between 0.5mm and 0.8mm spark plug gap a reputable tuner. Did they have a reason for the small gap?
He didn't mention anything to me about the small gap. He told me he was originally going to gap them down to 0.8mm. The plugs really shouldnt of needed much adjusting anyway as the bcpr7es come pre gapped at 0.8mm. He was also trying to say the miss was a 'skyline' thing lol the car feels great to drive but now im a bit skeptical on the tune if he cant even gap plugs.
15 hours ago, Ty1 said:

but now im a bit skeptical on the tune if he cant even gap plugs

Yeah I'd be too. It's strange when people say "reputable tuner", where did they get the reputation from? Instagram/Facebook or here on SAU? Or did they start off good and then got lazy/sloppy/dodgy (reminds me of a certain welder)?

Yeah I'd be too. It's strange when people say "reputable tuner", where did they get the reputation from? Instagram/Facebook or here on SAU? Or did they start off good and then got lazy/sloppy/dodgy (reminds me of a certain welder)?
I totally agree with you! The tuner did look after me though during the whole process and didnt charge me for a couple of dyno runs as we were diagnosing issues. And from what i could tell, he was a very honest, upfront guy. A mate of mine recommended him and a few of the boys on sau have had good results too. Im not too familiar with the pfc hand controller but is there a way i can view the fuel map/settings and post a pic on here so someone might be able to tell me if it looks like a decent tune?
On 28/04/2018 at 7:52 PM, Ben C34 said:

Keep in mind it probably wast the turner who gapped the plugs, could have been a different guy so not really fair to blame one guy

Yes sorry, I meant to finish off my previous post with this but I got distracted and hit the post button too early.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • So, I started this repair and got as far as "fixing" the holes with some fibreglass. God all those years working on boats came back quickly. I decided I'd reach out to some rust guys just to see what they would say about it. I came across a guy about 40 mins away and went to see him. He said the windscreen needs to come out, that there might be some more bits around the windscreen and he'd quote them at the time. But his quote was $300 to remove and replace windscreen and $3k for the damage he can see. He said he could respray the roof for $1200 and the bonnet for another $800 (somebody has previously rattle canned it, its horrendous). This is $5300 + any small additional bits. It's a lot, I get that and the name of one of my fave youtube channels 'Not Economically Viable' comes to mind.  I'm not being financially rational, but I've taken him up on the quote. He's opening a new shop in November with more room, so we're waiting for that. I'll leave the currently missing headliner out until then. I'm looking forward to it being fixed and having the paint looking nice again (lots of clear coat issues on the roof too). / flame suit on.
    • Oh and some up-and-comings; New rear drivers wheel bearing. I'll do that this weekend while the diff is out. The car is already up and the d/c axles and missing exhaust will help with space. This is the last bearing for me to do and I've been dragging my feet on it. I also have some new EBC blue stuff pads for the car and some new brake fluid. I haven't ever flushed the fluid in this car and looking forward to it. I have 600 degree fluid to put in. Not exactly "race fluid" but better than the typical stuff I have been using.
    • A proper clutch/plate type mechanical diff with quite a lot of pre-load and high locking % is better for drifting. Much more consistent in its behaviour. A helical can be annoyingly vague and inconsistent in how it responds under the sorts of abuse found in drifting.
    • Some updates here. I pulled the entire interior out, minus some trim to respray the seats with Colourlock dye. It turned out really nice though I accidentally let the dog in the car after and she scratched up the front seat.  This is what it looked like before, the colour was just washing out everywhere but thankfully the leather was in good nic. Then after the respray   And after the bloody dog jumped in The headliner is out waiting to be retrimmed, but it will stay out now until Nov - see why below. I replaced the stereo/headunit with a period-styled Android headunit. I have no after pics, but I'll get some. This is because of the missing pixels. I tried to fix this twice with replacement ribbon cables but couldn't. Also the bluetooth interface I'd bought for this was crap. Then there's the rusty roof. Pics and info in this other thread. I have decided to get this repaired professionally, but I'll update that thread. This is why the headliner will stay out for now. I'll be getting the roof and bonnet resprayed at the same time the rust is fixed. I also had an interesting issue with my drivers door lock.  For a small period I was having issues getting any 12v power to the car - I mean *any*. It would have no dash lights, nothing. It happened while I was at the shops and I couldn't get in the car. So, we had 2 problems. The most pressing here is that I was locked out. I have only a single physical key hole on the car, the drivers door and no amount of turning would unlock the car. Surely it doesn't need power for this? The second issue is why am I losing all power periodically, The battery isn't dead, its almost like the battery isn't even there. Two issues that were surprisingly easy to fix. You fellow BMW over-engineering lovers will appreciate this. The lock in the door has 5 states; mechanical lock, electric lock, neutral, electric unlock, mechanical unlock achieved at -90 degrees, -45 degrees, 0 degrees, 45 degrees and 90 degrees. Although, the unlock is towards the front of the car, so opposite for LHD countries. Sticking the key in and turning 45 left or right is what is used 99% of the time. It activates the central locking etc. 90 degrees is for dead battery access and, obvs, only un/locks the one door. But because the mechanical lock is never used and is 27 years old, it seizes up. I was totally unable to turn the key far enough to get to the mechanical unlock (At the time of locking myself out, I didn't even know this was a thing). I eventually did it with some vicegrips and teflon spray.  I made a quick vid for other E39 peeps.   The battery issue is totally new to me also - It wasn't making sufficient contact between the post and the terminal. The terminal was bolted on tight, but the car wouldn't have power. After checking the battery with my multimeter I accidentally contacted the terminal and the battery post and the car got power. The battery was only a few years old and in good condition. I cleaned the post and the terminal with a wire brush, bolted it back on tight and never had the issue again. I'm still surprised that despite having solid contact it didn't work. Also, the car was getting Warragamba sized pools of water in the back when it rained. My initial concern was another rust problem. But when I went out on Weds while it was raining and while I had no headliner in I could see a steady stream of water coming through the roof mounted aerial. As this aerial is for the (now removed) car phone I pulled it out and whacked a blanking grommet in the hole. It seems fine now. I'm thinking I might get the hole permanently filled when the rust is fixed. Moving forward and things in progress; The tailgate needs some attention. I have taken all the trim off to clean it all and address some small rust spots. I have partially done all of this but I'll finish it up hopefully this weekend. As all the trim are now entirely devoid of trim clips I have bought a heap of strong velcro and I'm hoping it does a good enough job as any of this trim in good condition is super expensive and usually in Europe as we dont have many of the wagons here. Suspension and brakes!!! This is exciting. In the front; New control arms New sway bar links New lower Eibach springs (the only modification I'm planning on this car) M Sport shocks (these came with the car and will replace the longer shocks in the car) New top mounts Used 540i calipers (stock brakes suck!) New 540i disks and pads (22x296 mm for 528 and 30x334 mm for 540i) New front wheel bearings (thank all that is holy for bolt on bearings!) Annnnd in the back; New control arms New sway bar links Adjustable air suspension arms (fool the car into what the current height is so the self levelling suspension can match the new front ride height) New ball joints I'll also be doing a brake fluid flush while I'm in there. I'm planning on switching the car over to the 16's that came with it so I can clean up and respray the M Sport 17's. They've lost a lot of colour over the years and have some gutter rash. None of this will start until the E90 is back.
    • You mean you will regret it for drifting duties? I don't quite follow.
×
×
  • Create New...