Quad-4 (1228707 ECM) Rough Idle Problem

[Shannen Durphey]

You sent a message to the list describing how the timing was erratic. 
I found the post, and the answer to my question.


> I have deciphered a little more of the ALDL data stream.  At idle:
> 
>  * Advance varies from 10-20 degrees in a somewhat random manner.
>    Why is the advance moving around?

You will not be able to measure the timing with the EST disconnected
unless you remove the appropriate terminal from the connector on the
IDI cover. 

If the timing really couldn't be adjusted, none of us would be here. ;
)

The 1991 W41 442 (Cutlass Calais) came with an MU1 transaxle, 3.94:1
final drive.  Calibration BCC is AXRM/3681, part no 16163680.  The W41
package was manual trans only.  If your local dealer can't get the
correct calibration for you to start with, you might try these
companies:

Jim Pace Pontiac, 888 - 748 - 4655
Allied, Inc., 800-589-4419 
Lakeview Automotive, 734-427-5800
KMB Warehouse, 800-475-1227

Tell them they were listed on Partsvoice.
Shannen


remaklus at attglobal.net wrote:
> 
> I didn't measure the timing with the EST disconnected, just listened
> to engine continue to idle roughly.
> 
> Also, the timing on the Quad-4 cannot be adjusted, the computer
> controls everything.
> 
> Shannen Durphey wrote:
> 
> > Hold on....  Tell me again how you checked timing, and what your
> > results were?  On the dizzy equipped 4 cyls, GM wants the timing light
> > connected to the coil wire so it flashes with every plug firing, and
> > the timing is set by the "averaging" method, a service manual way of
> > saying "a good guess".  The timing can really fluctuate on some of
> > those older engines, and I know that trying to time by #1 alone gives
> > bad results.
> > Shannen
> >
> > Will Remaklus wrote:
> >
> > > I also tried disconnecting the EST output from the ECM such that
> > > the ignition module controls the timing: no difference.
> > >
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