I am running the hahn lvl 5 kit and for the longest time i have been noticing (even before turbo) i have had a missfire at idle only, not enough to throw the light or code but enough for me to notice the pop out the exhaust at idle and the lean spike in the afr confirms a missfire as well as the drop in rpm recorded by hpt...

i have a few things i have tried, i have tried different gaps (my god have i tried em all )
also i have tried switching to regular stock oem plugs.
i have tried BKR7E and BKR8E (stock is BKR6E)

i have a feeling that it is a tunning issue because when i was running the stage 3 ecm this problem was not there i had even made note of it and would switch the ecm out and the problem would come and go with the change...


any help would be great.

 

who tuned it?

 

My car always pops and spits at idle. It's done that since I went to 60# injectors. I don't really worry about it.

ON another note I was throwing 0300 alot recently, but I think it was because of the WOT box.

 

well hahn, zzp, me, angelo (ravenss), jimboss....

thats what is weird it has been there threw out the whole time i have had the car no matter what set-up or tune i was running except the one and only GM STAGE 3 did not do it.

yeah i treat it as normal especially cause its not enough to throw the light.

yes, i agree that you problem was probably the box i have since disabled p0300 and 301,302,303,304 to avoid the light from 2-stepping

 

could be one of the coilpacks, is it the same cylinder misfiring?

 

mostly 2-4 but it is random through out all cyl.

 

do you have any head work done by chance?

 

I have had this same problem since I got my 60's.

 

nope! just a little massaging here and there on the intake and exh but nothing touched in the bowl area or no valve job of any kind.

hmm i heard that these pen style inj are **** for idle and drivability... i have no drivability issues but it does have a shitty idle, im thinking of switching to a walbro 255 and some 79# inj that are disc type that are supposed to be much much better.

anyone have any thoughts or comments on the RC 79#

http://www.racetronix.com/01D129xFM.html

 

i've been gettin that same problem recently and the only mod i have is a cai. i thought maybe it was cuz of the cold but i have no idea.

 

Those are the injectors paul uses.

 

It's pretty much a Cobalt thing. I have seen more people with "Random misfires" than any other problem with this car. Any mods at all cause it to misfire at idle, and every now and then when driving. Sometimes really bad to where it almost idles out the car.

Good luck figuring it out, no one else has yet. If you want some hints, I can tell you what it is not.
It is not any compression style problem,
It is not the plugs
There are a bunch of other things, but I forget now, its been a while. Good luck with it though.

 

hmm which leads me to belive that it is a issue with spark timing at idle... cause that flucuates at idle, and i think i have found a pattern with the timing and the missfire...

 

its supposed to fluctuate at idle though. The ECM maintains a consistant idle by advancing timing when the idle drops below its target RPM and retarding timing when the idle is above its target RPM. Its similar to the closed loop AFR feedback at idle. It's never quite at the exact number, so it always fluctuates to try and get it. I would try and raise the idling RPM and see if that does anything, course i know you manual guys have idles that are already pretty high

 

Try playing with the Idle Spark advance a little bit. It wont fix the problem as there tables we dont have access to in hpt that allow us to fix the issue. But it will help it some.

 

My car has done it since stage 2 was installed, it's annoying but hasn't ever thrown a code . I can see it on a tech 2 but only at idle or when downshifting.

 

with the right fuel tables they idle fine with zero misfires. check the adders. also, move the coils around and see if the misfire moves

 

dont listen to area...your misfiring cause your wingless..you want my sunburst highrise

 

which adders? im working on this bug again

 

shoot me your e-mail in a pm. i'll send you a fuel map that works well

 

my 60's started making my car throw a p0300 sometimes at idle. we had to disable it so i could pass inspection.

 

yeah im trying to find a solution not a band aid, lol i have already applied the band aid mod...