regarding lack of power...slight update

Jim Green
Tue, 27 May 2003 20:14:40 -0700 (PDT)

--- "Michael S. Williams"
<> wrote:
> At 7:17 PM -0400 5/27/03, Eric wrote:
> >>Are you sure on your cam timing?  This can cause
> backfiring even
> >>just a few teeth off.  I suggest the cam because I
> have done it
> >>before.
> >
> >im almost 100% positive i have it completely
> correct... the little
> >hash mark lines up EXACTLY with the top of the
> gasket for the valve
> >cover, the 0 on the flywheel is looks like "(" as
> it it perfectly
> >lined up w/ the marker on the bell housing as the
> bently states to
> >do, and the distributor is spot on.
> >
> >now, i did try moving it a tooth counter-clockwise,
> which should be
> >retarding it, correct?  i did not, however, try
> advancing it a
> >tooth... but if i advanced it a tooth, then that
> would put the mark
> >on the cam gear way further down compared to where
> it is supposed to
> >be...
> >
> >i guess i could try advancing it a tooth and see if
> that helps at
> >all... i'll go do that now, and report back..
> ok... reporting back... i advanced it a tooth (well,
> turned it
> clockwise), from the position where i said that
> everything lined
> up... it started harder, and the idle is even
> worse... but, the
> backfiring stopped...
> took it out for a short drive... same issue... as
> soon as boost hits
> full, the power starts cutting way back... it felt
> slightly faster
> than last time, but that was probably just a
> function of the timing
> being so advanced... im gonna put the cam back to
> the previous
> setting...
> i forgot to mention in the first message that
> someone suggested a
> vacuum leak, but when i did the oil cap test, the
> car immediately
> died... so it doesnt appear that there is a major
> vacuum leak that is
> happening, and i dont think that a vacuum leak would
> cause the power
> issues...
> one thing that i DID notice, however, was that there
> was a slight
> <pfft> if i went from boost to closed throttle...
> so, that would
> indicate that there is a hole in some part of the
> intake plumbing...
> but if that were true, then wouldnt that register as
> a vacuum leak?
> once thecar cools down... or maybe justtomorrow,
> i'll undo the intake
> plumbing and see what's going on... i didnt notice
> this sound before,
> though... so it might be something that i JUST did
> during my last
> adjustment session (i did take off the intake
> plenum)

If it was leaking under boost it would cause a rich
condition which would kill the power.  That's what I'd
look at first.  Doesn't explain the backfiring though.
 I'd venture to say that could be an idle switch not
letting the ECU know it should idle.  I've found most
low rpm backfires related to timing, so I bet
something is off sensor wise since you seem to have
the base timing set right.


Jim Green
'89 90tq

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