LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Help me read a few plugs?

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Old Jun 24, 2011 | 09:24 PM
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Default Help me read a few plugs?

Guys,

I have been chasing a lean condition on the passide of my motor and I pulled 2,4 and 6 plugs tonight. Can you take a look at these and let me know if any look like that cyld. is running lean?

CY 2:



CY 4:



Cy 6:



I know its hard to tell but CY6 is very sooty and looks to be rich where CY2 is pretty clean and the conductor on top is not even black, just a little white ashy color.

I'm going to swap my injectors from bank to bank as well and see if it could be one of them causing the issue.

I haven't pulled CY8 yet as I have to get to it from under the car.
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Old Jun 25, 2011 | 07:46 AM
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Anyone???
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Old Jun 25, 2011 | 11:16 AM
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I would say cyl. 2 looks a little lean.
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Old Jun 25, 2011 | 11:17 AM
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white= lean. black= rich. coco brown= GOOD
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Old Jun 25, 2011 | 12:31 PM
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for what its worth if you have the haynes manual or access to one there is a color page in the back that shows some mild to extreme spark plug situations.
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Old Jun 25, 2011 | 01:29 PM
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Yes, the PCM scanned thru datamaster is showing leaner on the passide and it's very prevelant at just before and at WOT. No vac or exhaust leaks and not sure what's going on? Trying to isolate it down to a cylinder.
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Old Jun 25, 2011 | 05:51 PM
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Originally Posted by guppymech
At WOT the PCM reverts to open loop and disregards the O2 sensors for fuel mixture and all fuel injectors receive the same pulse signal, correct? If so then maybe you have a bad injector like you thought. Have you swapped the injectors to see if the lean condition followed to the other side?
Correct, however it's happening even before PE mode is set and I'm thinking it's ignition related as the same thing was present in my previous recordings with the SVO 30s I had on there. I can try swapping them, but I don't think it's gonna do much good as Cylinder 2 is a little lean, so I'm gonna have my tuner play around with the individual cylinder fuel trims.
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Old Jun 25, 2011 | 06:10 PM
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It is often hard to get a good reading on LT1 plugs. This is due to the fact that the throttle body is at the front of the intake the front cylinders get the first look at the air. After running at low engine speeds and especially at idle the plugs will be progressively darker towards the back of the engine.
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Old Jun 25, 2011 | 06:33 PM
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No one tries to read plugs that have been driven on / ran for any amount of time.

If you're trying to look for a WOT lean condition you will need to put in brand new plugs, do only your burnout and a 1/4 mile WOT run and kill the ignition at the end if the run.

Then you will need a quality otoscope or you will need to cut the threads off the plug.
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Old Jun 25, 2011 | 06:37 PM
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Originally Posted by 1toofastlt1
white= lean. black= rich. coco brown= GOOD
On a WOT run the porcelain should be CLEAN (white) with a pencil thin fuel ring at the bottom.

If you're talking plugs that are old, as stated before, you're not going to get a good read on them. Idle can darken the plugs and tell you nothing about the rest of the operating range.
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Old Jun 25, 2011 | 06:45 PM
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Originally Posted by gregrob
On a WOT run the porcelain should be CLEAN (white) with a pencil thin fuel ring at the bottom.

If you're talking plugs that are old, as stated before, you're not going to get a good read on them. Idle can darken the plugs and tell you nothing about the rest of the operating range.

bingo...

The only thing that these plugs can tell you is if they are in the right heat range for your motor..
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