Problem with 3.1V6 (Ignition related)

[Shannen Durphey]

Have you tried tapping the ecm while the engine is running?  That's a
good, technical test to see if the ecm is working correctly. : )  Use
a screwdriver handle for it, firm but not damaging taps.   If you
remove the 5V bypass line from the module, does the car run better? 
Can you scope the REF input and EST output signals?  What happens if
you ground the ALDL terminals?

Are the injectors firing?  Some of the 6 cyls would lose one injector
driver, killing 3 injectors.  This shouldn't set code 42, but it would
cause the ecm to richen the 3 firing cylinders.  Simple noid light
will test that.

Ain't diagnosis fun?
Shannen


Scott Feaver wrote:
> 
> I am having a problem with a 3.1V6 engine, ignition related.  This car has
> DIS and a 730 ECM.
> 
> I changed the module because a pair of cylinders werent firing.  Didnt seem
> to help, so I had that replaced and got three coils as well (I have to drive
> 45 miles to get to the USA to buy the stuff at reasonable prices so I got
> all three :).   Changed the crank sensor and am getting a good reading off
> of it (about 1.4 volts AC with starter spinning motor).
> 
> I've done testing according to the factory service manual and it would
> indicate that the module is good because it is switching properly.
> 
> But what is happening is the motor wont rev higher than about 400 while it
> is trying to run.  And only indicating spark on two or three cylinders it
> seems.  Runs real rich, cat gets hot as hell, motor is running so rough it
> is almost falling off the mounts.
> 
> It is setting a code 42 after running for a few seconds according to Diacom.
> Also, a couple of times it said it was in Backup mode as well.  I am not
> getting any indication of Advance or reference degrees (they show zeros).
> 
> Anyone have any ideas?
> 
> I have also switched the wires for a new set as well.
> 
> Thanks,
> Scott
> 
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