Engine Wiring Harnesses Randomly Popping Loose?

[cc333]

My '94 K2500, once the major bugs were worked out (new water pump, distributor rotor+cap+wires, ignition coil, radiator, alternator and transmission), has been mechanically rock solid (good engine, decent body, nice interior), but every now and then, a sensor wire will pop loose under the hood and cause all kinds of problems (the TPS sensor harness once popped loose, and the truck would die unless I just barely tapped the gas pedal to get up to speed).

I'm sure the old plastic clips bending and breaking from age and heat fatigue is a probable cause, but is it normal? I could fix them with zip ties, I suppose, but I just want to know if it's a common problem, as I don't see many complaints about it.

It's been one of the major reasons I can't consider this truck to be 100% reliable, as this keeps happening, and I'd like to get to the bottom of this so I don't have to feel like I need to get a new(er) truck.

Even without this problem, I'm not sure I'd drive it across the country or anything (at least not without some upgrades to the interior, such as better seats), but it would be nice to be able to use it more regularly without worrying about wires popping loose al the time.

c

 

[Erik the Awful]

There are replacement pigtails for many of the underhood connectors. I've replaced a few of mine.

1994 CHEVROLET K2500 PICKUP 5.7L V8 Electrical-Connector Parts | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

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Use these to make your wire splices. Crimp them well, but don't try and crush them. Give a little tug test before you heat shrink them and they'll last a lifetime.
www.amazon.com/Haisstronica-Connectors-Gauge-Insulated-Waterproof-Electrical/dp/B07L29DLGN/

 

[xXxPARAGONxXx]

If the harness-side connector itself is the problem, you can purchase a new harness-side connector by itself. Remove the terminals from the worn connector using a terminal removal tool (e.g., Aptiv 12094429 and Aptiv 12094430), then re-install the terminals in the new connector. Most of the engine harness-side connectors are still available for purchase.

I would not cut off a stock connector and splice in an aftermarket pigtail unless you have to. If you can learn to just remove the terminals from the stock connector and re-install the same terminals into the new connector, that is the best practice. That way you maintain the integrity of the stock wiring harness and have a new connector. Best of both worlds.

 

[evilunclegrimace]

Most of the under-hood connectors are either weather pack (IAC, MAP, O2) or Metri pack (TPS CTS). You do need a special crimping tool to make proper crimps.

 

[cc333]

Hmm, I see. I guess connector wear out and replacement aren't as unusual as I thought?

If the harness-side connector itself is the problem

Yes, it's the harness-side. Specifically, it's the little clip that holds it to the sensor-side of the connector. The electrical contacts themselves appear to be fine.

Most of the under-hood connectors are either weather pack (IAC, MAP, O2) or Metri pack (TPS CTS). You do need a special crimping tool to make proper crimps.

Is this applicable when I remove the terminals, as @xXxPARAGONxXx suggested?

I forgot to add that when all the other stuff (distributor, water pump, etc.) was replaced, the dealership also replaced the harnesses and connectors for the ignition coil and fuel injectors, because apparently they pretty much fell apart when they removed them and the injector harness was particularly bad, as the wire insulation was severely frayed and at best was a short circuit problem for the ECM, and a fire hazard at worst because of their proximity to the fuel spray). For the ignition coil harness, I don't know if they replaced the whole harness or just the connector.

c

 

[cc333]

Also, while I'm here, what is the average life span of things like, say, the Throttle Position sensor, O2 sensor, the IAC, or any other engine sensor?

Given that most of them are likely approaching 30 years old (assuming none have been replaced in the meantime), should I consider replacing any/all of them as preventative maintenance, or is it best to leave them alone until something fails?

Assuming the odometer is correct and hasn't been tampered with, the truck has about 105k miles on it.

EDIT: And what about the injectors? The engine runs well right now (when all its wires stay put), so I don't think they're having any troubles, but should I consider rebuilding them with new seals and stuff so it stays that way?

EDIT #2: The transmission is newly rebuilt and only has a few hundred miles on it, so at least that shouldn't be a problem for a decade or two, provided it's properly maintained and not overworked/overheated

THIRD AND FINAL EDIT: My truck has the 7.4L V8, in case anyone's wondering....

c

 

[evilunclegrimace]

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[evilunclegrimace]

that is a weather pack connector ^ and here are the terminals.

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[evilunclegrimace]

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this is one version of a Metri pack connector

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[evilunclegrimace]

And here are one of the sizes available for Metri pack

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