P0300 Issues 1997 K1500

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Spareparts

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Your misfires look like mine except WAY worse. Hopefully mine is a fuel pressure problem and a new pump fixes it.
 

Schurkey

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Enough misfires will kill a catalyst. Murder it, really.

That said, "I" would concentrate on the misfires and worry about the downstream sensors later.

What is the plug gap? I think GM spec is 0.060, but I'd be happier at 0.040 using plugs with a shorter ground electrode. Have you checked the resistance of your "new" plug wires? Take a look at your "new" cap 'n' rotor, see if there's any sign of premature failure. Did you find ANY scarring of the plastic between the high-tension terminal and the low-voltage terminals of the coil, where it was occasionally arcing?

If there's no problems on the ignition side...yeah, I'd install an upgraded spider injection system.
 

Brocktoon

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I ordered a new ignition coil and managed to get it installed just as it began to snow here in PA. Except for #8, which did worse for some reason, all cylinders had either the same or fewer misfires. I'll have to check the wires, cap, etc later in the week, but it looks like I'm at least going in the right direction.

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Cyl. Misses 2/25 2/27
1.) ------ 12 ----- 12
2.) ------ 2 ----- 0
3.) ------ 46 ----- 4
4.) ------ 10 ----- 3
5.) ------ 28 ----- 26
6.) ------ 12 ----- 6
7.) ------ 56 ----- 21
8.) ------ 2 ----- 19


For the O2 sensor, I unplugged it on Saturday and began hitting it with Kroil, I plugged it back in today, and when I scanned for codes the P0300 was still there as expected, but the p0161 was gone. Does unplugging a component normally clear any related codes, the way disconnecting the battery clears all codes? At any rate, B2S2 seemed to be more consistent today than B1S2. It would occasionally spike briefly, but mostly stayed around 100 mV at operating temperature.

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Schurkey

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Disconnecting the battery clears codes on OBD1. Not on OBD2.

Putting penetrating oil on an O2 sensor is a waste of effort. The thing is sealed gas-tight, oil can't get in to do any good.

Yup, looks like the converter for Bank 1 is toast, or in danger of being murdered by excess misfire. The O2 sensor results are not happy.
 

Brocktoon

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I just got done installing the upgraded MFI spider, and for poops and grins swapped the 0.060" plugs for 0.040" at Schurkey's suggestion. Cylinders 1 and 2 are still misfiring, 3 through 8 were all good. At this point, I'll probably just have to take the truck in and have it looked at. I've done everything I can think of. Hopefully the worst of it is taken care of, I'm just tired of fighting with it for now.
 
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