That's true...under light throttle cruising, it pings pretty bad (IAC
controls idle). Had that happen to me twice (blown gasket).
- Bernd
-----Original Message-----
From: owner-dakota-truck@buffnet.net
Subject: Re: DML: RE: belly pan gasket
bernd@texas.net wrote:
> Vacuum leak.
>
> > Bernd,
> > Ok, you have to explain this one to me. If the pan gasket is leaking,
the
> > only effect is in the crankcase recirculation. The airway from the TB,
> > through the intake and heads, into the cylinders has not been
compromised.
> > Everything is metering normally. How can a lean condition occur?
Anyone with an A/F gauge (it really don't apply to everyone else because
they are
guessing) - do this simple test: While warm and idling (gauge oscillating)
pull
off one of your main TB vacuums and leave it open (massive vacuum leak).
Watch
the gauge - what happens? You get a very temporary lean condition but
shortly
thereafter - the PCM compensates by pumping more fuel - then the PCM
realizes this
is now a higher rpm than requested (idle) so it adjusts the IAC by closing
that
orifice (IAC is simply a controlled air bleed or in other words: a
controlled
vacuum leak) until the desired/scheduled rpm is reached. Guess what the A/F
gauge
is doing now? Oscillating around Stoich (14.7) as if a normal situation
(albeit
pretty jumpy due to the lack of a more precision "control" orifice. If the
vacuum
leak is so big that the IAC plunger closes completely before the
desired/scheduled
rpm is reached, a MIL is set.
Think about it.
Latr,
Shane
-- '96 IndyRam-HisIndy-MPI/TB/Pulleys/AccelCoil/MPComp/HookerSuperComps/CompTAs '96 IndyRam-HerIndy-numbered(#142)"Track Truck" '74 Triple-Black Dodge Challenger Rallye 360 home-brew EFI R&D vehicle '68 Black Corvette Convertible 427 (For Sale)
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