flashing MIL?

[Thimble]

This has been a minor issue ever since I put in my cam in last year (240s duration 111 lsa) - 2001 C5 Corvette. The idle lope is pretty choppy, and this is known for setting off a false misfire detection.

I have the P0300 code set to "not reported" on C6001, and "no MIL" on C6002.

During periods of long idling only, the MIL flashes. No codes are reported (through the dash DIC) when this occurs, so I assume it's still the misfire detection having some effect. If I rev it up a little bit over idle so it smooths out, the MIL light goes out.

It doesn't bother me so much, as I know what it is...but anyone who looks inside the car while it's idling inevitably asks me about it.

I looked at the misfire parameters and tables. If I set C6602 to a high enough temp that misfire would never be tested for, will this work, or would it be unwise to do so?

Any other suggestions/possibilities?

Also, if it could be something other than a misfire detection setting this off...why can't I pull up a code for it?


Thanks,
Tom
:cheers:

[dc_justin]

Have you adjusted tables C5621 - C5627?

[Thimble]

Have you adjusted tables C5621 - C5627?
No, I have not.

Should I have, and if so, is there any info on how to properly do so?

[dc_justin]

If you're having misfires at idle, I'd start with raising the idle misfire value. This allows for a longer period of time between cylinder events before the PCM determines that a misfire has occurred.

[Thimble]

Thanks, I will try that.

I guess the thing I still wonder about though...if the misfire code is set to no MIL and not reported, why does it still flash the light?

:cheers:

[Blacky]

If I rev it up a little bit over idle so it smooths out, the MIL light goes out.
Hi Tom,

You could also try increasing C5606 to the RPM where the cam smooths out.
That way the misfire tests won't run when the engine is idling under that RPM.

Also to help deterine that is is in fact a misfire code (even though it is probably false misfire due to the cam), try logging the following PIDs:

GM.MFTOTAL,
GM.MFFAIL,
GM.MFPASS,
GM.MFCYLxC (where x is 1..8)

Regards
Paul

[Thimble]

You could also try increasing C5606 to the RPM where the cam smooths out.
That way the misfire tests won't run when the engine is idling under that RPM.
That seems a better method than what I was thinking. I will definitely give that a try.

Thanks a lot for the quick replies!

:cheers:

[Bruce Melton]

Tom,
Not to pile on here, but if you get a good VE tune done the cam will really smooth out at idle and transiton off idle much better.
You have plenty of cam there to sound snorty but it can be smoother I bet.
Bruce

[Thimble]

If I make it any smoother, I will want a bigger cam. :D