Jump to content
SAU Community

Recommended Posts

Hi Guys,

Just wondering, it seems that when my car is idling it has a really faint miss every couple of seconds or so, nothing major and it drives fine under load and makes good power, just wondering if this is normal? It's hard to describe but its kind of like instead of having a constant purrr for the idle every 2-3 secs theres a slight quiet and then it starts purring again.

anythign to be worried about? Car is an R32 GTR.

Link to comment
https://www.sau.com.au/forums/topic/161260-slight-miss-on-idle/
Share on other sites

I guess its fairly normal. Try new plugs first see if it helps. If not then get your injectors cleaned see if that works. I've just got my injectors done and its a fair bit better. Yet to see if there are any improvements in fuel economy yet tho.

Mine has done it ever since moving away from the heat range 5 1.1mm gapped plugs.

If I open the gap up the idle smooths out.

The miss is stuff all but I guess it can be an annoyance if you expect it to be baby smooth. No such thing with a modified car. :)

Mine has done it ever since moving away from the heat range 5 1.1mm gapped plugs.

If I open the gap up the idle smooths out.

The miss is stuff all but I guess it can be an annoyance if you expect it to be baby smooth. No such thing with a modified car. >_<

I found the exact same thing going from 1.1 to .8 gapped plugs.

iv got his problem aswell and iv changed my plugs and put new spitfire ones on and no change

This can also be caused by resistor pack and wiring to the resistor pack.

Or even earthing of the resistor pack.

Most get a lot of heat over the years and need some attention.

You will know there is a problem when you operate the air-con.(at idle) and it misses regularly.

  • 1 year later...

Have we figured this out? I just changed from 5 plugs gapped to 1.0mm to 6 plugs gapped at 0.8mm and now I have this half miss stumbling sound coming from the exhaust every few seconds. Any updates?

Edited by cpt_impossible

Maybe get new coilpacks and clean the injectors like what others have said above?

I've noticed that this has started happening to my car as well. It's got splitfire coils and a change of the plugs about 3 weeks back and no change. A clean of the injectors might help, but too much a hassle. Everything is running good except for the idle so it doesn't bother me.

Yeah it happens when your spark plugs are gapped too close: from wiki

The gap adjustment can be fairly critical, and if it is maladjusted the engine may run badly, or not at all. A narrow gap may give too small and weak a spark to effectively ignite the fuel-air mixture, while a gap that is too wide might prevent a spark from firing at all. Either way, a spark which only intermittently fails to ignite the fuel-air mixture may not be noticeable directly, but will show up as a reduction in the engine's power and fuel efficiency. The main issues with spark plug gaps are:

· narrow-gap risk: spark might be too weak/small to ignite fuel;

· narrow-gap benefit: plug always fires on each cycle;

· wide-gap risk: plug might not fire, or miss at high speeds;

· wide-gap benefit: spark is strong for a clean burn.

A properly gapped plug will be wide enough to burn hot, but not so wide that it skips or misses at high speeds, causing that cylinder to drag, or the engine to begin to rattle.

I have mine gapped at 0.6 because my coilpacks are shit and i need new ones, but it fixes my hi-rpm misses, so until i save up for some splitfires i hav to put up with the missing at idle,

So yeah check the gap on your spark plugs, ideally should be 0.8

I have the same idle-popping issue.

Regarding plugs, I've read that the amount of resistance with power getting to the plug can change the ideal gap for your engine. So I guess a lengthy trial-and-error testing period is going to be the best way to get things the way you like them.

Edited by Legumis

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

    • For once a good news  It needed to be adjusted by that one nut and it is ok  At least something was easy But thank you very much for help. But a small issue is now(gearbox) that when the car is stationary you can hear "clinking" from gearbox so some of the bearing is 100% not that happy... It goes away once you push clutch so it is 100% gearbox. Just if you know...what that bearing could be? It sounding like "spun bearing" but it is louder.
    • Yeah, that's fine**. But the numbers you came up with are just wrong. Try it for yourself. Put in any voltage from the possible range and see what result you get. You get nonsense. ** When I say "fine", I mean, it's still shit. The very simple linear formula (slope & intercept) is shit for a sensor with a non-linear response. This is the curve, from your data above. Look at the CURVE! It's only really linear between about 30 and 90 °C. And if you used only that range to define a curve, it would be great. But you would go more and more wrong as you went to higher temps. And that is why the slope & intercept found when you use 50 and 150 as the end points is so bad halfway between those points. The real curve is a long way below the linear curve which just zips straight between the end points, like this one. You could probably use the same slope and a lower intercept, to move that straight line down, and spread the error out. But you would 5-10°C off in a lot of places. You'd need to say what temperature range you really wanted to be most right - say, 100 to 130, and plop the line closest to teh real curve in that region, which would make it quite wrong down at the lower temperatures. Let me just say that HPTuners are not being realistic in only allowing for a simple linear curve. 
    • I feel I should re-iterate. The above picture is the only option available in the software and the blurb from HP Tuners I quoted earlier is the only way to add data to it and that's the description they offer as to how to figure it out. The only fields available is the blank box after (Input/ ) and the box right before = Output. Those are the only numbers that can be entered.
    • No, your formula is arse backwards. Mine is totally different to yours, and is the one I said was bang on at 50 and 150. I'll put your data into Excel (actually it already is, chart it and fit a linear fit to it, aiming to make it evenly wrong across the whole span. But not now. Other things to do first.
    • God damnit. The only option I actually have in the software is the one that is screenshotted. I am glad that I at least got it right... for those two points. Would it actually change anything if I chose/used 80C and 120C as the two points instead? My brain wants to imagine the formula put into HPtuners would be the same equation, otherwise none of this makes sense to me, unless: 1) The formula you put into VCM Scanner/HPTuners is always linear 2) The two points/input pairs are only arbitrary to choose (as the documentation implies) IF the actual scaling of the sensor is linear. then 3) If the scaling is not linear, the two points you choose matter a great deal, because the formula will draw a line between those two points only.
×
×
  • Create New...