Diagnosing GM efi..

[Christopher Bruno]

peter paul fenske wrote:
> 
> Howday
> 
> Well that is high, huge vacum leak, injector not firing,
> low fuel pressure, clogged fuel filter, mismatched cal.

I'm thinking vacuum leak but I don't think it is the head
gasket 'cuz it used to run OK with the carb. and I haven't
done anything since.  I thought about the injector not firing
but it seems like the car idle does drop down a bit when
I unplug each injector one at a time.  Fuel press. measured
at 45-47 @ idle.  Now, the mismatched cal I hadn't thought
of.  Are you talking about the memcal?  On the 85's is that
the second smaller chip?  The car this came out of was an
IROC with an automatic and probably slightly different gearing
than I have but I would think that with my bigger tires that
should be negligible.  I would think overall the two cars
should be relatively comparable (85 Camaro vs 84 S-10 Blazer).
What do you think?


> 
> For the blm to creep up that o2 must be working
> >>scanner, the BLM was up to 158,

According to the scanner the O2 does swing back
and forth once it gets into closed loop. I even
replaced the O2 sensor for kicks...
> 
> The default MAF not working is a crude N-alpha
> Based on constants using TPS and RPM

That makes sense...
> 
> Naturally if BLM is outa wack the constants
> aren't gonna work well, My vette 88 cal
> runs nice with MAF disconnected albeit a bit rich.

How so?  Wont the computer use the N-alpha and then
just enrich based on BLM?  Or is that so crude that
it really couldn't hope to get close?

> 
> >Beleive that applies to the 165's 86-89 ecms.
> 
> Actually the default N alpha only sets when
> MAF is bad. Software mode is still operational.
> Not quite backup mode.

Do you think I ought to set to limp home mode and
see how it runs?  What could this tell me?  Possibly
bad IAC valve?
> 

Thanks guys! I appreciate your help...
> >
> >Cars hate Modonna clothing

LOL!

-Chris