[Diy_efi] Effect of detonation on measured mixture?

[Shannen Durphey]

Shawn Fogg wrote:
> 
> Shannen,
> 
> "and that it only lights the malfunction indicator lamp if the misfire is severe enough to cause catalyst damaging emissions."
> 
> Nope, it actually has 10 different faults for misfires. 4 for each cylinder 'non-catalytst damamging', 1 for > multiple/random cylinder misifire 'non-damaging' 
This means "We can't determine which cylinder is doing it but we need to turn on the
light."

> then 5 more the same again except for catalyst damaging. No damaging will be logged as pending the first time around then will light the MIL on the second fault. The damaging codes flash the MIL on the first occurance.

 This is what I meant.  I should have been more specific.  You do realize these are
mandated failure conditions by the US EPA?  These are not exclusive to, nor
indicative of the quality of, the engine management software in your car.  

> 
> The system is actually pretty sensitive. With the original version of the software in the DME I know a few guys that added the same supercharger as I have and they started getting misfire faults at idle. The extra load, and this is an Eaton with a bypass valve, was making enough of a change to trigger the non-damaging faults. Later software versions for the car actually desensitized this a little.

Early gm systems were so "sensitive" that they would flag bumps on the road as
misfires.  Well, they did cause changes to the crankshaft acceleration rates.  But I
wouldn't call that sensitivity, I would call it "in need of improvement."

> 
> If you put a bad plug in or have a slightly loose wire it will 'see' it and give you the fault.
Just like the gubbamint says it should.  You can buy a Chevrolet Cavalier and get
the same "sensitivity." 

Oh, well.  It was just a suggestion.
Shannen

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