Quad-4 (1228707 ECM) Rough Idle Problem

[mike mager]

Uh, did anybody else catch that (or do I need better drugs?)?
[complete quotation below]

[this is quoted from the FTP site:]
<ftp://ftp.diy-efi.org/incoming/Quad-4%20Idle%20Miss.pdf>

>"Very high overlap cams will exhibit an "eight stroking" phenomena . . . "

Sure, well known, and a two-stroke-cycle may analogously 'four-stroke'.

>" . . . pumping out a cylinder full of unburned gas . . . "

Alright, lotsa unburned fuel (HC), sure
               - but -
lotsa unburned _air_(!). (at ~20% O2!)

>"The over-rich exhaust will not contain enough oxygen for the catalytic 
>converter . . . "

Here it is - What?
The unburned air is ~20% oxygen, radically more than _any_ combustion event 
could _ever_ put out!  The EGO reads the oxygen (O) in the exhaust (E) gas 
(G), not the HC.

<brag>
Ima ASE certified drivability mechanic, and . . .
</brag>

It is common for a plain-old Motor City rig to have the EGO read a dead miss 
as a too-lean condition, just _because_ of that ~20% O2 in the unburned air 
after a misfire.

What are they getting at?  (or what did I miss?)

Mike (an IR intake helps to 'tame' high overlap)


>From: Shannen Durphey <shannen at grolen.com>
>Reply-To: gmecm at diy-efi.org
>To: gmecm at diy-efi.org
>Subject: Re: Quad-4 (1228707 ECM) Rough Idle Problem
>Date: Thu, 06 Apr 2000 19:08:16 -0400
>
>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


______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com

----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org