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So finally got my motor built tuned and AFR pretty much dead nuts 14.67 or Lamada 1.00 for those guys.
BUT always a butt - Been chasing a gremlin CEL light that will just Randomly start flashing for about 1 to 2 min max then will turn off completely like nothing happened. Mind you when it comes on the car runs perfectly fine and honestly I dont even notice it sometimes except for the flashing orange light catches my eye and like wth...
I have scanned the car for codes multiple multiple times cause this happens everytime I drive the car and it always goes back off like it never happened without me doing anything I just keep driving and it goes off. And when I check codes there are ZERO codes found, ZERO Pending, its like nothing ever happened. Drive cycle is still complete in the scan tool nothing pending its very odd.
Now my engine is a 5.3 Alumimun Darton Dry sleeved block punched out to 427. It does have a lil Custom cam in it Ported LS7 Heads, c6 Z06 Bottom end running a wet sump oil system LS3 pan. Fast 102 intake NW 102 all the basic NA bolt-on Goodies.
Car runs fantastic just cant figure out why that dang light comes on then goes out just really bugs the **** out of me.. I dont know where to start cause car runs so strong and i have ZERO Codes. Great oil pressure plugs look clean ect...
Electrical issue maybe? but where to start I just dont have clue...
Thank you VERY MUCH for ANY ideas or help in tracking this gremlin down!
Flashing CEL is a failure that can cause damage to a catalytic converter. 90 percent of the time it's a misfire. Knock sensors can cause a CEL flash too.
if you have a scanner that can look at live data look at the misfire counters.
If you have access to a snap-on scanner look in obd2 generic under group 6 and you can see misfire counts for the current drive cycle and the past 10.
Flashing CEL is a failure that can cause damage to a catalytic converter. 90 percent of the time it's a misfire. Knock sensors can cause a CEL flash too.
if you have a scanner that can look at live data look at the misfire counters.
If you have access to a snap-on scanner look in obd2 generic under group 6 and you can see misfire counts for the current drive cycle and the past 10.
i have access to HP tuners an i can defintily log all live data and have logged misfire as you suggested which i do have some because of the size of my cam. I have been told some misfire with cams are going to expected an normal? I just dont know how much is to much an why it triggers an then goes off like nothing ever happened.
Again why would there not at least be history stored in the ecm of the event i guess is my question?
i guess my confusion is why its not being stored in the ecm in pending or history? Its like the misfire never happened?
why no history?
You're not getting ANY codes? I had an intermittent miss a while back, and the code (forget the #...) was dutifully stored each time. If I tried to accelerate it would go to limp mode sometimes. Good thing I could clear them on the spot....
You're not getting ANY codes? I had an intermittent miss a while back, and the code (forget the #...) was dutifully stored each time. If I tried to accelerate it would go to limp mode sometimes. Good thing I could clear them on the spot....
Yeah zero codes stored or saved. An the car runs fine even when it is actively flashing. Or at least runs good enough i cant tell any performance change an def does not go limp mode.
Just about every cammed vehicle needs the misfire tables adjusted at idle/low speed depending on how big of a donkey dick cam you have. The "chopity chop" from the cam makes the PCM thinks its missing.
However, IMO, it's a bad idea to max out those tables and turn the DTC's off becacuse if you ever have an actual misfire, it's not going to throw a DTC.
Something else you can do, even if the DTC's are turned off, you can log each cylinder misfire counter in the HPT scanner and see which cylinders are showing misfires.
You mentioned that you tuned it to a 14.7. Is that at idle or cruise or both? With something with a big cam, they run better if they are a little richer than stoich at idle. The other thing with a big cam, you can't really trust the WB at idle because if the cam has a lot of overlap, the WB is going to "show" rich.
When I tune I always disable p0300 because it's a joke of a code. But while you're looking to see if p0301-p0308 are enabled, check if they are on Mil on first error
Also the reason I look at misfires on mode 6 in obd2 generic is it has better luck at seeing misfires vs looking at the actual misfire data on the vehicle specific side.
Just about every cammed vehicle needs the misfire tables adjusted at idle/low speed depending on how big of a donkey dick cam you have. The "chopity chop" from the cam makes the PCM thinks its missing.
However, IMO, it's a bad idea to max out those tables and turn the DTC's off becacuse if you ever have an actual misfire, it's not going to throw a DTC.
Something else you can do, even if the DTC's are turned off, you can log each cylinder misfire counter in the HPT scanner and see which cylinders are showing misfires.
You mentioned that you tuned it to a 14.7. Is that at idle or cruise or both? With something with a big cam, they run better if they are a little richer than stoich at idle. The other thing with a big cam, you can't really trust the WB at idle because if the cam has a lot of overlap, the WB is going to "show" rich.
Thanks for the reply LilJv10
So it does it when just normal driving really not even getting on it or anything. Never seen it come on at idle at all that i noticed.
AFR is 14.7 All around for 90% or better of the time minus when i get in it of course And yes when cam is Choppy at idle AFR will dip rich some not to bad though corrects quickly..
CAM Specs - attached
I have logged each cylinder for misfire in hp tuners and all seem to be about the same. But I need to do some more data logging tbh and note when it comes on the CEL so i can review that part of the log.
So got out and did some logging today and definitly confirmed with my HP Tuners Scan tool that Cylinder 4 is my misfire culprit. Now how to solve the issue... I have already changed the wire and plug right out the gate and that didnt solve it. So I am guessing Swap a coil test, then swap and injector and test, and if all 4 of those plug, wire, coil, injector fail - What would be the next thing to test or check Crew?
In many cases it has been reported that the cylinder labels on the hptuners misfire detection do not always correspond to the cylinder numbering the motor uses. I would make sure which cylinder is really misfiring.
In many cases it has been reported that the cylinder labels on the hptuners misfire detection do not always correspond to the cylinder numbering the motor uses. I would make sure which cylinder is really misfiring.
This is a good point to bring up. It's not just HPT though. It's the nature of the beast so to speak.
Double check that the plug wire is not resting against (or extremely close) the exhaust. I suppose you should check all the plug wires for that matter since tracking misfires by cylinder can be misleading. Is the CEL flashing at the same intensity all the time or is it sometimes flashing less brightly on occasion? I ask because I had this issue a long time ago and the flashing was brightness was inconsistent. My issue was a plug wire arcing on the header tube. Good luck!
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Flashing CEL Randomly - IDEAS/Thoughts? 
And yes when cam is Choppy at idle AFR will dip rich some not to bad though corrects quickly.. 
