Missing in action - still
robert at s-cars.org
Sat Oct 2 12:36:45 EDT 2004
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
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
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?
Random Bushism: "The future will be better tomorrow." Governor George W.
Robert Myers 304-574-2372
urS6 - Cashmere Grey
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