Mizz96Z28

As the title suggests I'm going through spark plugs for some reason. I had NGK g-powers in the car last season (car details in sig) and towards the end the car starting misfiring and idling rough. So I made new wires to see if that was it and it didn't make a difference so I changed the spark plugs to stock heat range AC delco rapidfires gapped at .045" and it's starting to misfire again with only 300 or so miles on them. In my procharger manual it says stock plugs should be ok for using with the low PSI system and since it's intercooled and that .045" gap should be fine also with a high energy ignition but somethings obviously off. If my car is running lean under load could that make the spark plugs die quicker? I need a better A/F gauge to find out if it is in fact too lean or not, but now that it's not running right I don't want to drive it to find out. Anyone else have a similar set-up as me with spark plugs that last or any other recommendations? thanks

Myles

slick1hunting

do some reading on how to read plugs preferrably with good pictures. It is pretty easy to tell if the heat range is good. I also would check gap on plugs you pull. I would probably try a smaller gap. I am loving my wideband setup it sure makes a guy more confident. Have you tried running any data logs? I also would look under the hood in the dark for any arcing.


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slick1hunting

an ir temp gun can also be handy to tell lean and rich cyllinders


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Injuneer

What went wrong with the plugs .... carboned up, electrodes burned, gap opened up excessively?

Running lean increases combustion chamber temps, which will burn the electrodes and open the gap. Pull a plug - check the gap, check the appearance, as noted in the posts above, compare the plug appearance to online photos on spark plug manufacturer's websites showing various plug conditions. Or even post a photo.

Other than that, there's no way we can tell from your description what is causing them to "die".

Mizz96Z28

I have an IR gun and used it to try and find which cylinder was misfiring, figuring it would be colder since it was only firing occasionally but I couldn't seem to get consistent readings. One the 1st set of plugs I took out (the NGK g-powers), the gap is at .038" and I set them to .037" so that didn't change much. The electrode tips seems fine and the coloring is a light rust brown color with some light gray coloring on the ceramic part of the electrodes. 2 plugs have some black soot and look wet which should be the ones that were misfiring and I think they were cylinders 7 and 8, which is weird it was both back cylinders misfiring. I should've marked what cylinder each plug came out of so I can take pics of each and note where they came from, oh well I'll remember for next time. All in all the plugs to me look OK physically.

Myles

slick1hunting

A few things I will mention 7-8 usually are a little colder as they have to fight the hardest to get the air so they may or may not be the misfires. If you look at individual cyl fuel trims you will see the differences. Pretty much the o2 sensors get the average of all four cyl on its respective side so one could be lean and one rich and two decent and their would be little fuel correction and plugs would indicate what each one is doing pretty much spot on. What I am saying is sometimes (because of the fuel correction ) the good looking or bad looking plug may not be the problem cyl. Seeing the fuel correction is very helpful. Thats why fouled o2 sensors can have a noticable effect and why datalogs and live data are helpful in troubleshooting. Read your plugs for the heat range and run the right heat range for your car(not what is said may be ok). Confirm you have your ltcc grounded well. For me I use my temp gun roughly an inch from header flange( I vary it a little but maintain an equal distance from flange). Idle will probably read different than off idle unless your tune is really close. Off idle I place something in throttle linkage to hold it between 1500-1900 rpm (a button works pretty good). This may show the misfire or it can show the individual cyl fuel trims may be off(given good reading as its a low tech way with room to error) . A wideband or egt probe on each cyl is the "real" way of doing things........... What makes you think your problem is the plug rather than injector or valvetrain or ... I also would ohm your wires to be sure you got your ends on good without damage.


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Mizz96Z28

It's the plugs because I've already changed them once because they were doing the same thing and it went away for awhile when I put in new plugs. I also changed the wires 1st just to rule them out since it's alot easier to do wires on my car than plugs. What's throwing me off is the car was running awesome, felt right and sounded right, and then boom, starts misfiring and doesn't clear up until the plugs are changed. So something is causing them to fail (in my mind anyways) and that's what I'm trying to figure out, like whether I have the wrong heat range for the car or what. Was hoping people with an LTCC system on their car and an intercooled supercharger might've had a similar problem and fixed it by using a certain heat range plug, etc, and replied to this post. The heat range for my 1st set of plugs according to the way they looked (brown and gray color) seemed to be the right range for the car ( I think they were colder, will have to look up part # to find out) and they lasted longer than the ones I have now which are stock heat range but they still failed so could that mean I need to go 2 heat ranges different than stock maybe or not necessarily? Is it likely iridium plugs might be a better choice with this ignition?

Myles

slick1hunting

I think your not reading your plugs correct for heat range. Disreguard any color and all that and look only for this( will look for a link)


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slick1hunting

how to read spark plugs - Google Search


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slick1hunting

look at the ground strap only looking for were it has the color change you want it near were it begins to bend or curve. My guess(total guess) is you should be two steps colder and gapped between .035-040. Call nkg tech line or one of the plugs tech lines also.


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slick1hunting

that link didnt bring up the picture I was trying to show. its the second picture I believe ( a single plug closeup). You can see the change in color on the ground strap


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97WS6SCharged

I always ran TR6 plugs with my Vortech even with the LTCC. I would give them a try and gap them at 0.035. Also try swapping your 7 & 8 coils for 1 & 2 and see if the plugs on those cylinders display the same symptoms.

Fatdog2

My # 8 plug was always covered with gunk and oil,till I got the intake manifold gasket replaced.Not a blown car,but the repair fixed that issue.hope this helps.

Mizz96Z28

Alright, I have an update. I pulled the latest set of spark plugs (2nd set to misfire thus far) and remembered to number them when I took them out this time. Cylinders 1-6 are running way too lean. The ground strap has white/light gray ash on them and the porcelain is white. Cylinders 7 and 8 look good with no white/gray ash on them at all. So at this point heat range I think is a secondary problem, meaning the least of my worries at the moment. Why would 6 out of 8 cylinders run lean? It could be clogged injectors but that seems odd since its the 1st 6, or maybe a clogged fuel filter. My fuel pressure regulator is stock with 118,000 miles on it so I think I might change that to a brand new adjustable whether its the problem or not. I have a fuel pressure gauge so I was going to use that tomorrow when I get home from work to see what my fuel pressure is and maybe that can lead me in the right direction. What do you guys think? Could it be a tuning issue? My tune was done by MadZ28 a few years ago. I wanted to have it dyno tuned but it won't run well enough for long enough for me to get that done (don't have access to a car trailer). I also don't have any tuning software at the moment either to see what the car's doing while running.

Myles

Injuneer

How do you add the extra fuel required for boost? 2-bar MAP/tune? boost refeferenced FPR? FMU?

What were the gaps on the plugs you pulled that you indicate appear to be running lean?