Missing in action - still

[Ed Kellock]

Try swapping spark plugs around.  I know they're new, but that seems
to be the only thing you haven't tried (unless I haven't been
following this as closely as I think).

Ed

On Sat, 02 Oct 2004 12:36:19 -0400, Robert Myers <robert at s-cars.org> wrote:
> 
> OK, I've been busy.
> 
> The miss in #4 ('95 urS6) is still with me - intermittently.  <grrrrrrr>
> 
> Yesterday I redid the wiring harness to the coil pack with solder joints
> and shrink wrap instead of crimps.  The reason is simply that I feel more
> sure of myself when soldering.  I put the coil pack back into the car and
> fired it up.  Miss still there.  Location #4 (as before).  Swapped PSO
> connectors.  Miss did not move.  Therefore (it sez here) the problem is the
> coil.  So, out comes the coil pack and in goes a new coil at position
> #4.  Put it back in the car and the miss is still at #4.  OK, I had to run
> an errand.  I took the truck instead of the S6.  Got back a half hour later
> and fired the S6 up.  NO MISS???  I took it for a 60 mile drive - no
> troubles whatsoever.  Came home parked the car in the garage and went to
> bed - exhausted.  This morning I fired it up and the miss is back.  Swapped
> PSO wires again.  Did not move (again).
> 
> Pulled out Bentley.  Checked the wiring diagrams and the component location
> diagrams and saw where what I though were the ground connection for the
> coil primaries are, in fact, the +12 volt supply for the coils.  Apparently
> the PSO grounds those lines to create a current change in the primary which
> then causes the secondary to pulse the spark plug.  That's opposite of how
> I thought it worked but...  I checked the voltage at each of those
> connections at the firewall with ignition both on and off.  All gave 12
> volts (nominal) with ignition on and zero with it off.  Did the same tests
> at the PSO connector end of the wiring harness with identical results.  OK,
> the wiring harness is at least continuous through the coil primaries and
> there are no shorts between any of the wires and ground.  I had already
> replaced coil #4 with a brand new one yesterday so the secondary for #4
> should still be OK.  Perhaps it's not impossible that the new one might
> also have been faulty but I kinda doubt it.
> 
> Since swapping connectors at the PSO did not move the miss the PSO and
> connections to the PSO from the ECU are OK.  If one of the PSO channels
> were not operating then the miss should have moved.  It didn't.  The
> ignition system appears to be OK.
> 
> That leaves injectors.  I checked resistances of injector wires from wire
> to ground.  One side showed high (infinite) resistance.  The other side
> gave a very quick reading which then shot up high before the el-cheapo
> meter could stabilize long enough to get a reading.  This behavior was
> consistent at all five connectors and with several repetitions at each
> injector connector.  I'm not sure exactly what this tells me but at least
> there appears to be no differences between position.  They all behaved the
> same.
> 
> I replaced injector #4 with one of the injectors I pulled out when doing
> the RS2 upgrade.  Miss still there.  The injector may be faulty - or
> not.  Can't tell from these results.  It's possible (unlikely but...) that
> the injector I swapped in might also have been faulty.  I doubt it.
> 
> The plugs are brand new.  The cigar for #4 was brand new with the coil
> yesterday.
> 
> If the problem is a fuel issue then about the only thing it could be is
> that injector #4 might not be getting the "fire one" signal.  How do I
> check this?  If the signal is missing then how do I solve the problem?
> 
> I suppose I could pull the fuel rail again leaving the injectors installed
> in the rail and see if #4 sprays when the starter is cranked.  Better have
> my fire extinguisher handy.  Any better suggestions?
> 
> Beuller?
> 
> Bob
> Random Bushism: "The future will be better tomorrow." Governor George W.
> Bush, Jr.
> _____
> Robert Myers  304-574-2372
> Fayetteville, WV
> urS6 - Cashmere Grey
> _____
> 
> 
> 
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