What will cause LS1B to not report misfire ?!

[wesam]

I have one strange problem with 2003 C5
It will not repost misfire even if i unplug one of the spark plugs wire or injector wires
CASE already done many times
Stock tune file installed with same problem
Any help will be appreciated

Thanks in advance

[joecar]

Stock 2003 C5...?

[wesam]

No it has built engine with stock ls9 cam

[wesam]

Attached the tune file

[spedracr93]

I doubt I'm much help, but as a reference - My LS1B won't record misfires as a code either. I have double checked the MIL settings and it's set to do it, but I'm not sure what the parameters are for it to do so.

When I had bad misfires under load I would get a blinking CEL but still never got the hard code.

[joecar]

My theory: the non-stock engine's misfire somehow falls outside the stock misfire detection...

play with the misfire tables C56xx until you see misfires, and then back off a little

When you did CASE relearn, did engine stumble correctly, and after engine shutoff did PCM have time to save results...?



edit: this part somehow got left off by Tapatalk (on my phone).

[aaronc7]

I have a 2003 Z06 with a cam and since returning the misfire detection tables back to stock values, i get an occasional random misfire code and check engine light. Usually right after a cold startup at idle.

[Highlander]

If you have specific codes, misfire will be disabled. If you have any airflow codes or other codes. I've been considering on doing a custom OS just to eliminate this check and have misfire in speed density mode.

[wesam]

It has just p0102 because its SD tuned
No other airflow codes

[Highlander]

20764

[Highlander]

Then you won't be able to have Misfire detection.

[RADustin]

this is interesting. So basically all COS files that are SD do not have misfire detection?

[Highlander]

They have Misfire Detection if you are in MAF mode. if you are in SD mode then you don't... Do you really need this?

[RADustin]

actually - I think it would have helped a week or two ago when my brothers truck had an intermittent coil ground problem on the passenger bank. We had a SD file loaded in it trying to autoVE but kept having mechanical issues, eventually finding the problem. We always wondered why it didn't throw any codes.

It maybe isn't really needed, but its good to know it's not functional when in SD mode. the knowledge is more useful than the actual PCM detection.

[joecar]

I'll make a note of this somewhere.