Hello,
About a month or so ago I noticed my Century (3300) was idling rough at stop lights and such. Found that a mouse had chewed through a fuel injector wire as well as a spark plug wire. Replaced the fuel injector wire (spliced) and all spark wires, as well as all spark plugs for good measure. Engine ran as smooth as butter for about three weeks, and now is performing (rough idle) the same as before. I inspected the connections between the plugs and boots on the wires, and the wiring on the fuel injector wire. No damage or poor connections.

The only theory I have is that the wires are cheap and fragile, and one just failed due to poor quality. The plugs and injector wire are ACDelco, but the plug wires were thin, and Chinese made. In pulling a boot off its plug, the metal inside of the boot just stuck to the plug and came right off the boot. Have ordered new ACDelco spark wires.

Can cheap plug wires be expected to fail so early? Even cheaper ones? Or does another problem I haven't considered seem more likely?

What kind of 'splice'?

What carfixer007 said ^^^^^^^

. . . and yes spark plug wires that are cheap can cause this. No good reason to go cheap on plug wires. They are going to be in there for a long time.

hello, thanks for replying. Attached is an image of the splice of the new and old wire. Could be that’* the wrong term for it. Had it covered in electrical tape before but removed the tape to inspect the wires/connectors. Splice kit came with the new fuel injector wire.

I wouldn't rely on crimp splices for that. I'd solder it. It might work for a while, but a soldered connection will work better for longer.

Not a proper splice.

if you remove the tubing and the connectors from the left 2 injectors, then untape the harness you can get access to the wires better for any repair, not needing to lean so far and being able to put some heat shrink tubing over the fixed splice (whatever it may be)
If you have the right crimp tool, those are fine, but since it was never heat-shrunk id just assume it wasnt crimped right either. If you have solder skills you can easilly make a simple splice with the wires and flow solder into them.


But if you dont, they make a heat shrink tube with solder, its not perfect but they have a place. Any heat shrink tube you use, id recommend marine because it has epoxy inside that flows out when heated, making it much better sealed and strengthens it. The wires wont live a high stress life where they are at, thankfully

Replaced all spark plugs wires. Improvement in idling as to be expected (one wire was broken) but idle is still rough and engine lags on acceleration. Over the last few months it'* been getting harder and harder to start. I'm thinking it could have low fuel pressure. Thoughts, anyone?

Also good call on the crimp job. The connection is working right now (I unplugged it and engine sounded much worse) but I will solder it when I get home for winter break.

Thanks

Could be fuel pressure. Could be other things.

What is the fuel pressure with key on and engine stopped?

What is the fuel pressure at idle?