I am posting this so that people who search for this same problem in the future have one possible solution to a misfire under boost.
When I got the car on the road I had an old set of almost fouled ACDELCO's in the car... it ran fine but had a random cyl misfire at high rpm's......
I went and put in some NGK TR6's.... gapped them to .030. Right from the first minute I drove with them I knew there were problems...
Until the car heated up, they misfired at 4500 rpm's in 3rd no matter what I did... eventually this would clear up and it would drive fine. Now - this wasn't your regular misfire, it sounded like a machine gun in the engine bay and really REALLY hampered performance....
Then, the car started to run a little worse... and a little worse...
Until (get this) 6 days after installing them, they started to misfire right at startup - this would persist for about 10 minutes... I would literally run on 3 cylinders.
So - today I tore them out of the car, went and got some $2 Champion copper spark plugs (stock heat range), and gapped them at .032 and threw them in.
I have driven about 150 km now... NO misfires at idle, NO misfires when the car is cold, and NO audible misfires in the top end. My CEL did blink a random cyl misfire at me at 5500 rpm in 3rd but I think it was because I Might have hit the MSD Rev limiter which cuts spark. The car is far smoother in the power band now and it's VERY solid in the higher RPM's.. the car feels 4000x better now.
Either way, it has solved my problems. I will be putting in a set of 1 step colder ACDELCO plugs at the end of the week, these were just temps until I could get my hands on some.
All in all, I'm much happier, and now you have a bit of info to keep in the back of your mind.
Take care.
-Chris-
-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...
didnt I tell you to check the resistance of those NGK's?????
Glad you figured it out
SPD RCR Z -
'02 Z24 420whp
SLO GOAT -
'04 GTO 305whp
W41 BOI -
'78 Buick Opel Isuzu W41 Swap
dont go ac delco man, autolites, i had a set and have nothing but good things to say about them. ive had both a set of ngk and ac delcos break and the declos ended up ending my last engine. champion plugs are generally junk and these will fail on you too, autolites bud, youll like them.
btw what happened to those super expensives plugs you were so proud of?
parting out my built and boosted 97 z24 so4x4.com/cavy.html for pics and a parts list
Im running a/c delco rapid fire #5 plugs gapped at 035.I never got 1 misfire code.Ive had ngk's,champion,you name it,and i always got random missfire codes.I used to have denso irridiums.The car ran good with them,but there too expensive.Id go with #5's if i were you.The part number is 25164643 if you need it.
Peter
'06 Cobalt ss/sc W/G85 Package
Gm Stage II W/2.79" Pulley
K&N Drop In Filter
Custom Magnaflow Dual Exhaust
^^ I am also running AC DELCO RAPID FIRE # 5s gapped at .032 and after 10k boosted I finally had a misfire like he explains. A machine gun sound and it scared the crap outta me. MY CEL also came on and was blinking. I then replaced them and it is fine again. I strongly reccomend these plugs but you should change them or check them every so often . Good to hear you got it worked out.
<img src="http://img.photobucket.com/albums/v292/dragmyz24/shoppedcav2.jpg">
Rush Racing
http://www.gettherush.com/
Rapidfire #5's here as well. I had a misfire, but added a few grounds and helped clear it right up.
i have rapid fires #5 also.
For the Rapidfires is the part number #5??
FU Tuning
ive had the stock gm charger plugs, ( missfired) raped fire # 5's ( missfired) and the what ever the # 5 cross over to in the NGK plugs, only the NGK's dident miss fire.
gaped at like .030
and here im pulling 5 -6.5 lbs of boost.
i also notesed it ran alot smother,
chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
Hey Jay, where did you add the grounds? Thanks.
2000 Z
Running with the supplied plugs from the GM S/C's Delco & GM's recommended 0.050 gap, I had two misfires in a course of 9-months. Not bad, so I'll stay with these.
I will be getting the RKS boots to get a better spark.
In my case, closing the gap was not a good idea.
>>>For Sale? Clicky!<<<
-----The orginal Mr.Goodwrench on the JBO since 11/99-----
everybodys experiences will be different. What works for one, may not work for another. .050 does seem a little much but if thats what is working for him then mine as well not fix what is not broken in my opinoin. I do run rich at idle with mine gapped at .032 but when I widened the gap it caused mine to mifire. .
<img src="http://img.photobucket.com/albums/v292/dragmyz24/shoppedcav2.jpg">
Rush Racing
http://www.gettherush.com/
told you it had to be the plugs --- same thing with mine
Quote:
Ya maybe no misfires. But when I had them closed up (0.030) I had rough ilde, and it was not burning as clean. As if was not doing a complete combustion, and my fuel mileage was worse.
See I would not run a ..50 gap on boost, I also would not have went to a .032 gap from a .050 gap. I would go with a .045, or .040, and that would probably be great for you.
The crappy idle was because it was running rich at idle, which I get that as well with the 370cc injectors at idle.
FU Tuning
mine idles great at .030. hesatates a little when it first starts, but after it goes in to closed loop its fine.
chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
I might be opening up the gap on my 1 step colder delco's when I get them. These still don't want to run right until they're 100% warmed up... I have a feeling my rich startup coats them in carbon and it takes a lot for them to clean up...
-Chris-
-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...
mr goodwrench- save your $ on them RK boot thingy's.
^^I already bought them. As of now, I have heard mixed reviews (a little more good then bad) but the concept of these things is worth a try. Besides, it will not break my bank account.
John Higgins wrote:Quote:
Ya maybe no misfires. But when I had them closed up (0.030) I had rough ilde, and it was not burning as clean. As if was not doing a complete combustion, and my fuel mileage was worse.
See I would not run a ..50 gap on boost, I also would not have went to a .032 gap from a .050 gap. I would go with a .045, or .040, and that would probably be great for you.
The crappy idle was because it was running rich at idle, which I get that as well with the 370cc injectors at idle.
John,
Trust me I tried them all under 0.050 and none worked well for me. I guess my coils are strong and want a bigger gap.
When I get the boots, I will try for 0.055 and 0.060 as there is less resistance.
and
You are right, I was running lean, I did not like it one bit. With the large amount of soot to told me that combustion was not complete, after one day of easy driving my tailpipe looked like a 5-10 year old Mitsubishi, I even wondered if I was blowing out smoke.
Not to mention some shake at idle and gas consumption increased slightly. Like I said before, during the time I can say I did not get a misfire, but like a million other things happened
Seriously if GM says 0.050 then 0.050 it is. I was open for suggestions, I tired it and well... unfortunately for me it did not work.
>>>For Sale? Clicky!<<<
-----The orginal Mr.Goodwrench on the JBO since 11/99-----
Mr.Goodwrench-G.T. wrote:^^I already bought them. As of now, I have heard mixed reviews (a little more good then bad) but the concept of these things is worth a try. Besides, it will not break my bank account.
John Higgins wrote:Quote:
Ya maybe no misfires. But when I had them closed up (0.030) I had rough ilde, and it was not burning as clean. As if was not doing a complete combustion, and my fuel mileage was worse.
See I would not run a ..50 gap on boost, I also would not have went to a .032 gap from a .050 gap. I would go with a .045, or .040, and that would probably be great for you.
The crappy idle was because it was running rich at idle, which I get that as well with the 370cc injectors at idle.
John,
Trust me I tried them all under 0.050 and none worked well for me. I guess my coils are strong and want a bigger gap.
When I get the boots, I will try for 0.055 and 0.060 as there is less resistance.
and
You are right, I was running lean, I did not like it one bit. With the large amount of soot to told me that combustion was not complete, after one day of easy driving my tailpipe looked like a 5-10 year old Mitsubishi, I even wondered if I was blowing out smoke.
Not to mention some shake at idle and gas consumption increased slightly. Like I said before, during the time I can say I did not get a misfire, but like a million other things happened
Seriously if GM says 0.050 then 0.050 it is. I was open for suggestions, I tired it and well... unfortunately for me it did not work.
I understand. I will agree on getting the RK boots I have them as well on my n/a cavalier.. For the price I think they are worth it.
On the opther note you were nto running lean, but rich with the close gap.
FU Tuning
QUOTE]On the opther note you were nto running lean, but rich with the close gap.
Yes you are right... again. I was thinking one thing and typed another, my fault. Sorry for my misunderstanding.
I was running extreamly rich.
>>>For Sale? Clicky!<<<
-----The orginal Mr.Goodwrench on the JBO since 11/99-----
I ran a ground from, the wire that goes into the negative terminal of the battery, into the frame where the top of the radiator bolts to the frame.
And also, from one of my idi cover bolts, to one of the strut tower bolts.
Fairly simple.
I've had 1 misfire since my S/C install (Feb 05), and I'm pretty sure it was because I bounced it off the fuel-cut rev limiter with cheapo gas (swifty or something prolly)
I'm using the Kit's plugs gapped at .050.
I've been running pretty much nothing but V-Power gas since then (hey, the shell station's on my way home from work :p), and just last weekend (May 15) I went autoXing, and was RIDING the rev limiter (1-2 second's worth in 2nd gear per run) with no issues.
Talk about screamin demon, the corner workers in that section of the track knew something was up in my J
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Sleeper style, they don't see it coming that way.
