PCM Output Voltages - O2 Sensor Issue Diagnosis

[Cincinnatus]

Dtc's? Ohm all the injectors too

[evilstuie]

Dtc's? Ohm all the injectors too

No DTCs but working from a stock VY Commodore tune setup at the moment.

I didn't get a chance to ohm check the injectors yet tomorrow I'll check the bosch part number and find the spec and test them all.

I pulled the #5 & #7 plugs though, and strangely one looks like it's never fired, the other completely black and fouled.

So it goes:
#1 Never fired
#3 Black/Fouled/Wet
#5 Never Fired
#7 Black/Fouled/Wet

I'll test each coil tomorrow for spark, change the spark plugs again for another 4 and ohm the injectors.

Wondering if there's another way to test if the cat is clogged without removing it because it's a bitch to get to the bolts holding that piece of pipe to the joiner for the headers.

[kojab]

Forget about the cat. Get the engine to run on all 8 cylinders With so many cylinders not firing would explain why you have different temps on the exhaust pipes.

If the current engine has not been running for some time you might find #1 and #5 and more fuel injectors have become jammed and not opening.

Be aware a jammed fuel injector will still ohm correctly. You don't need to remove the injectors to check if any are jammed (stuck closed).

[evilstuie]

Forget about the cat. Get the engine to run on all 8 cylinders With so many cylinders not firing would explain why you have different temps on the exhaust pipes.

If the current engine has not been running for some time you might find #1 and #5 and more fuel injectors have become jammed and not opening.

Be aware a jammed fuel injector will still ohm correctly. You don't need to remove the injectors to check if any are jammed (stuck closed).

I don't think they're jammed as the clean ones were still wet.
I'm chasing plugs, coils, and leads at the moment to eliminate those.

[evilstuie]

Latest update:

All injectors have about 12.4ohms (left and right bank)
made up new spark leads, confirmed they were all good, 180 compression on all 4 cold (not that I have a choice at this point)

Tested shutting off 1,3,5,7 injectors while running with HPTuners and NO difference in engine.
Shut off 2 and got a stumble, shut off 4 as well and it died shortly after.

Tried again switch between 1,3,5 & 7 and it made no difference at all to the motor.

Continuity tested the injector wires back to the PCM, all good.

So far we have 12v on injector rails, good connection to injector ground firings on PCM end of the harness, coil grounds good, ignition control wires matching up.
As I suspected in the beginning it looks like the PCM has faulted.

[Phoenix]

Have swapped injectors between banks and see if the problem follows the injectors? Have you swapped coils between bans?

[Cincinnatus]

If injectors are firing, and coils are firing, how is it PCM? Need to know injectors are spraying and actual plugs are sparking (not a spark tester as plug could be fouled)

[evilstuie]

Have swapped injectors between banks and see if the problem follows the injectors? Have you swapped coils between bans?

Not yet, but I have a set of near new 36lb injectors I could throw in to check.

If injectors are firing, and coils are firing, how is it PCM? Need to know injectors are spraying and actual plugs are sparking (not a spark tester as plug could be fouled)

I've tested the spark plugs by removing them from the head and putting an alligator click on the thread and grounding it and looking for a direct spark visually.

[Gampy]

I've tested the spark plugs by removing them from the head and putting an alligator click on the thread and grounding it and looking for a direct spark visually.

Testing like that works good for everything up to the plug, although it is not a positive plug test, a plug may work in atmospheric pressure and fail under cylinder pressure ...

As has been said multiple times, swapping items from side to side or hole to hole, is the best low cost approach.

[evilstuie]

Yeah I swapped the plugs around 1 to 3, 5 to 7, but had the same clean/dirty result.
I'll try new injectors and another set of spark plugs though to see if there's any difference.

Plugs are TR6 as the heads had 30thou shaved off when they were ported.
I could try TR55's and see if there's a difference, but it would happen to both sides, not just one.