As i've heard, many of us with boost (turbos, at least) have seen a flashing CEL when running at very high RPMs for even short periods of time. Those I've talked to (hypsy) told me that it was probably the ignition system not keeping up with the engine speed, therefore missing a spark, therefore allowing unburned fuel into the cat, triggering the post-cat o2 sensor to flash the CEL, warning of a cat-damaging condition (unburned fuel). Has anyone come up with a solution to this problem? At one point, I had a dis-2 installed, but I had to take it out before I had the chance to see if the same result still occurred.
cel only flashes for engine miss fire
Try changing your spark plugs. Try some NGK TR6's (#4177 I think), gapped to .035. It solved my problem. However, it will sill multiple cylinder missfire if you're not running proper air/fuel ratio. When I was running really lean it did it to me near redline, even with my plugs gapped to .035. Hope that helps a little.
I have the same problem and i was about to make a post about this im going to experiment with some denso plugs for the eco the pn is ITV16 but on Denso's site it shows 16 as being a fairly hot plug
Denso Heatranges they have all the way up to a ITV27s
THeres still some things I dont understand like what gap I should be running with boost and what the changing of the gap actually does, and this concept of blowing out the spark under boost? Changes to this the msd might have an effect on? I'm not sure what heat range of those listed I should be running? Do I want the coldest plug out there? I just dont know so if someone can give me some details that would be great
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
Retard your ignition timing one or two degrees at high RPM, it will go away.
well im not turboed but i am supercharged and running 10.5psi. When i first got the car done and was tuning it i got the flashing CEL as well at higher rpms for a few seconds then it would go away, after scanning it and tuning it with my apexi and my plx wideband i found out a few things had caused this... 1) My plugs were gapped at .50 and this was way too large for the boost i was running 2) My FMU was set at about 12:1 so i was seeing way too much fuel under boost 3) I did not have my apexi SAFC2 tuned in right under boost
Basically the flashing cel comes from being wayyyy too rich under boost. Find a way to get your a/f ratio correct throughout the rpm range and you will see your flashing CEL go goodbye. The best way to do this is using a datalogging wideband but if you do not have one it can be achieved by simply being careful and reding your plugs, in the past ive tuned cars using this method in conjunction with a scan tool to read the knock counts, this isnt the best way to tune but it will work.
607 Motorsports is your one stop performance and car specialties shop, we can do anything your imagination holds. Check us out at www.cardomain.com/id/jimmyc99z24
I dont see how being rich is my problem being the afr is in the 13s and 14s when it does it
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
rob (the one with the vette) wrote:As i've heard, many of us with boost (turbos, at least) have seen a flashing CEL when running at very high RPMs for even short periods of time. Those I've talked to (hypsy) told me that it was probably the ignition system not keeping up with the engine speed, therefore missing a spark, therefore allowing unburned fuel into the cat, triggering the post-cat o2 sensor to flash the CEL, warning of a cat-damaging condition (unburned fuel). Has anyone come up with a solution to this problem? At one point, I had a dis-2 installed, but I had to take it out before I had the chance to see if the same result still occurred.
Ok question. You have a flashing (or had) a flashing CEL, but never checked for sure to see what it was? If you had you would have never posted what you did above. not trying to flame you. More than likely as said a flashing CEL is cylinder misfire. Could be plug gap(more than likely, boost blowing spark out).
FU Tuning
ive tried gaps all the way down to .030 and it still does it
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
Yeah i've been fighting this code forever it seems...all sorts of gaps an tried pulling fuel...still get it every few pulls. An i've asked a few times but never recieved an anwser of how the PCM determines the car is misfiring....can anyone explain please????
Kyle
ive been told a lean condition can cause this code also
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
Rodimus Prime wrote:ive tried gaps all the way down to .030 and it still does it
Good post. I'm running tr6's now and had my first cel flasshing (missfire) last night, after a month of no problems and 4 passes at track.
I'm open to ideas, as i'm trying to get a msd dis 2 to ensure its not blow by.
Jimmy, can i assume ur using an apexi tunnning tool to fix this??
Nate
Evolution of Cavyboy-->C22t--> C24na--->c24s/c
1995 Cavalier W/2k1 Engine
GM S/C 13.940@99.78pmh w/2.068 60ft
Nate you assume correctly, i use the apexi SAFC2 in conjunction with a plx wideband, i datalog some runs with the plx and then just correlate the rpms and a/f to the apexi, it takes a bit of math but right now ive managed to get my a/f pretty constant at 12.2, i dont really wanna go any more lean that that, i do have some curves we have set up though to run 110 octane in it next year. My ultimate goal is 12's
607 Motorsports is your one stop performance and car specialties shop, we can do anything your imagination holds. Check us out at www.cardomain.com/id/jimmyc99z24
i have a msd dis 2 , doesnt make any difference towards resolving the problem
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
i put the denso irridium plugs in #5339 i think straight out of the box. i have never had a problem. no cel codes what so ever. and the throttle responce is great.
i think im going to try those when i have some cash im down pretty low right now
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
