Re: Quad-4 (1228707 ECM) Rough Idle Problem

[remaklus@attglobal.net]

Shannen,

The ECM is correct for the engine. Unfortunately, I have not yet been
able to obtain the correct (factory) calibration.  This is because I
bought the engine more or less new (race team spare).  Hopefully I
will be able to get a copy of the factory cal.

All of the sensors came with engine and are likely the same as the
HO 2.3.  One problem which makes this more difficult to solve is
that GM did not produce very many vehicles with the W-41 (190 HP)
Quad-4 engine.  The HO 2.3 (180 HP) is plentiful, but not the W-41.

When I finally get this engine to idle smoothly (and more importantly
pass emissions), I look forward to tweaking the calibration to see
if I can improve things.

-Will

Shannen Durphey wrote:

> Will, I've got a few questions.
>
> 1) I know you've mentioned this, but please tell me again:  Do you
> have the correct calibration and ecm that was originally used with the
> HO 2.3 engine?  Is this what you are using now, while you
> troubleshoot?
>
> 2)  Are all your sensors the same as the HO 2.3 engine?  How different
> is your configuration from the factory HO car?
>
> 3)  Have you spoken to anyone that has a vehicle that was originally
> released with this engine?  Do they have the same problems?
>
> Shannen
> Will Remaklus wrote:
> >
> > david garnier wrote:
> >
> > > I haven't been paying all the close to this thread, I
> > > appologize if I am off base...
> > >
> > > I have seen rough, unsteady or idle that never seems
> > > to smoothly come down, until maybe the engine starts
> > > to warm up.  Dumb question, when was the last time
> > > you removed your IAC and cleaned the pintle and
> > > mating seat with gas or cab cleaner?  I am amazed at
> > > the difference cleaing the pintle and seat will do on
> > > idling.
> >
> > I pulled the throttle body about a month ago and cleaned
> > it and the IAC pintle.  There was very little build up
> > to remove and hence I did not get any improvement.
> >
> > Here are some new findings on the problem:
> >
> > In pursuit of trying to understand my rough idling problem I
> > decided that the 2X reference pulses from the ignition module
> > did not provide enough resolution.  Therefore, several weeks ago
> > I fabricated a 24 slot crank position sensor using an IR LED and
> > photodetector.  The .pdf file:
> >
> >  ftp://ftp.diy-efi.org/incoming/Quad-4%20Idle%20Miss.pdf
> >
> > shows the instantaneous RPM, that is RPM calculated based on the
> > time between two adjacent slots in the wheel, versus time.  I also
> > included the slot number off the wheel to aid in identifying the
> > relative position of the crank.
> >
> > The first page is the engine at idle.  Notice that it appears
> > that all four cylinders fire, followed by two revolutions of
> > little if any power.  In contrast, the second plot, at 1900 RPM,
> > shows a much better situation: an increase in crank speed as each
> > cylinder fires.  At first I thought that the engine control
> > computer was causing this, but now I am pretty sure that is
> > not the case.
> >
> > While surfing the net I located the following:
> >
> >   Very high overlap cams will exhibit an "eight stroking"
> >   phenomena at idle where each cylinder will completely misfire
> >   on every other compression stroke...  This phenonmenon is
> >   responsible for the loping idle of the older hot-rod V-8s.
> >   Unfortunately, with every other exhaust stroke pumping out
> >   a cylinder full of unburned gas, hydrocarbon emissions soar.
> >   The over-rich exhaust will not contain enough oxygen for the
> >   catalytic converter to complete its breakdown of unburned
> >   hydrocarbons, so even with the cat in place it will become
> >   ineffective.
> >
> > The above explanation seem to perfectly describe the problem
> > that I am having.  The exhaust is very rich, yet the catalytic
> > converter is not all that hot (or glowing red, like it did
> > years ago when I had an ignition coil go bad!).
> >
> > Therefore, it appears that the problem is likely caused by
> > something in the top end.  When I checked the timing chain
> > several weeks ago I verified that at TDC the camshaft alignment
> > dowel pins went in easily.  As such, the only things left to
> > check are the lifters and the cams.
> >
> > Any ideas?
> >
> > -Will
> >
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