Bad running after manual swap

[JPVortex]

If you don't have good ground engine-body and body-frame (and thus engine-frame), there may be tramp currents in strange places, and attendant voltage offsets (V=IR) between different "grounds" on the vehicle.

Ground wires are every bit as important as "power" wires, even more-so because grounds often provide a shared current path for multiple devices... which means, if the ground is bad, some devices can cause effects on others for mysterious reasons.

Can you tell me this: What's the return path for the current from the coil to the spark plugs? Remember, it has to get back to coil, somehow. Think about it.

Fix the grounds!

That is true, it's only $8 at the auto part stores for 15 inch ground straps, and I'll need 2.

For $16 and an hour of work its worth it. Even if it's not the "problem" it may prevent further problems.

The return path for the coil to the spark plugs probably isn't great right now. Lol...

 

[1998_K1500_Sub]

That is true, it's only $8 at the auto part stores for 15 inch ground straps, and I'll need 2

Make sure they're big enough (thick, wide) to handle some current, e.g., Standard Motor Products B12G Engine Ground (which I just happened to Google, as an example).

Much of the return current to the alternator has to find it's way through those straps.

Those itty-bitty ground straps 1/4-3/8" wide... I wouldn't use.

 

[JPVortex]

Make sure they're big enough (thick, wide) to handle some current, e.g., Standard Motor Products B12G Engine Ground

Much of the return current to the alternator has to find it's way through those straps.

Looking at the junkyard, they had factory grounds still. None of them seemed to be all that thick at all. Looked someething like this.

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[JPVortex]

Also, just took a copy of the wiring diagram and crossed off everything in red that can be ruled out as the problem. The ECM, ICM, fuses, the replaced black coil connector, etc. The green circles need to be looked into still.

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[Road Trip]

That is true, it's only $8 at the auto part stores for 15 inch ground straps, and I'll need 2.

For $16 and an hour of work its worth it. Even if it's not the "problem" it may prevent further problems.

The return path for the coil to the spark plugs probably isn't great right now. Lol...

I'm with the Nitro Junkie, electrical troubleshooting with a bad ground plane is
like troubleshooting on top of jello.

But troubleshooting on top of a solid ground plane is like troubleshooting on top of granite.

As you said, even if restoring the grounds to new/better than new condition doesn't fix
the problem, if it clears up phantom/ghost errors competing for our attention it's well worth
the improvement in our collective focus on the real issue.

Glad to see that you are taking the long-term outlook on all this.

This is gonna get fixed, one way or the other. Hopefully sooner rather than later.
:0)

 

[JPVortex]

I'm with the Nitro Junkie, electrical troubleshooting with a bad ground plane is
like troubleshooting on top of jello.

But troubleshooting on top of a solid ground plane is like troubleshooting on top of granite.

As you said, even if restoring the grounds to new/better than new condition doesn't fix
the problem, if it clears up phantom/ghost errors competing for our attention it's well worth
the improvement in our collective focus on the real issue.

Glad to see that you are taking the long-term outlook on all this.

This is gonna get fixed, one way or the other. Hopefully sooner rather than later.
:0)

Yeah the grounds HAVE to be fixed, not something to be overlooked, once I know that’s solid, if the issue still occurs I can move on from that, knowing that’s not the problem at all.

I’m hoping and praying i can figure this out soon! The shop I brought it to has exhausted all their options, so it’s time for me to figure this out.

 

[1998_K1500_Sub]

Also, just took a copy of the wiring diagram and crossed off everything in red that can be ruled out as the problem. The ECM, ICM, fuses, the replaced black coil connector, etc. The green circles need to be looked into still.

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Yeah, I think you got a couple of "wires crossed" in the drawing.

- The coil wire you've circled in green. I'm not too suspicious of it.

- The wires to the ICM are in red. They are still on my radar.

With hope, the new grounds may clean up some spurious voltages (assuming they exist now) that are causing the ICM to trigger erratically, generating the odd tach "jumps" and other ignition / engine anomalies.

... but if they don't, at least you're better off. GM put them there for a reason, that's a fact. If they weren't necesssary GM would have kept the money in their pocket.

 

[1998_K1500_Sub]

Looking at the junkyard, they had factory grounds still. None of them seemed to be all that thick at all. Looked someething like this.

You'll need to stuff a 3/8" bolt through one ring terminal to bolt it to the head.

I assume the other end, at the body, is similar... 3/8' or maybe 5/16"

Ditto at the frame.

The strap you pictured looks like one for grounding the hood to the body, pretty light gauge.

You want a strap that's comparable to the wire leading FROM the alternator (6ga maybe, 4ga?).

Think of it like plumbing; size all the pipes to handle the maximum flow.

All the current FROM of the alternator has to find its way back TO the alternator. It ain't goin' through the engine mounts

 

[JPVortex]

Yeah, I think you got a couple of "wires crossed" in the drawing.

- The coil wire you've circled in green. I'm not too suspicious of it.

- The wires to the ICM are in red. They are still on my radar.

With hope, the new grounds may clean up some spurious voltages (assuming they exist now) that are causing the ICM to trigger erratically, generating the odd tach "jumps" and other ignition / engine anomalies.

... but if they don't, at least you're better off. GM put them there for a reason, that's a fact. If they weren't necesssary GM would have kept the money in their pocket.

I dont know how it'd be the wires from the coil to the ICM though. The issue started with the old connector(its a double sided connector, 1 end to ICM and 1 end to ign. coil so easy to replace) and I did think it could be those, because the previous owner spliced into it for some reason and it was shorting, which gave my finger a shock, so at the junkyard I picked up a replacement of them. Replacing them made no difference at all, problem stayed the exact same.

 

[JPVortex]

You'll need to stuff a 3/8" bolt through one ring terminal to bolt it to the head.

I assume the other end, at the body, is similar... 3/8' or maybe 5/16"

Ditto at the frame.

The strap you pictured looks like one for grounding the hood to the body, pretty light gauge.

You want a strap that's comparable to the wire leading FROM the alternator (6ga maybe, 4ga?).

Think of it like plumbing; size all the pipes to handle the maximum flow.

All the current FROM of the alternator has to find its way back TO the alternator. It ain't goin' through the engine mounts

Would something like this do it?

I'm just worried it won't be at all long enough. I dont know if it'll be long enough for the frame to firewall OR the firewall to cyl. head.

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