2004 Jeep Wrangler, inline 6, 166K miles and daily driver. Several years ago, I had the battery cables replaced because of corrosion issues. The shop that did the work was sloppy and left the old cables cut, disconnected and dangling. I thought it was sloppy work but did not complain because I thought it was just cosmetic. I thought because these were disconnected on both ends that there would be no risk of shorting something out.
Fast-forward about 2 years. Been having intermittent starting problems. Cold start seems to be getting a little rough to turn over (relative to normal). I decide to just keep an eye on it. From a warm start, after a quick trip to the store for example, the start is even rougher. I’m starting to get worried that I might end up getting stranded somewhere. But the next morning on a cold start, all seems well. I had noticed this for a week or 2 and was just monitoring the situation. Battery is less than one year old at this point.
I try to do the easy things – replace air filter. Makes no difference. One morning, it won’t crank at all and all the gauges are bouncing when I try to start. I’m late already so I take another vehicle. As a precaution, I order a new starter, ignition switch and clutch safety switch just in case.
That evening, I decide to try the old bang-on-the-starter-with-a-hammer to diagnose the starter. It doesn’t work. I get to poking around inside the hood just looking for something amiss. I note the old, cut positive cable just dangling so I attach it to the engine block ground and try again. It turns right over but will not stay running unless the accelerator is depressed. I poke around some more and find the old negative cable just dangling. So, I attach it to the engine block together with the positive and try again. The engine starts and it runs good as new! While it is running, I remove both loose cables and it stays running. I drive around the neighborhood and park.
Next day, it starts up just fine and so I drive it to work. I go out to lunch and it starts fine. When I leave at the end of the day, it starts fine. I make one stop on the way home and again it starts fine every time. I make it home and park. Later, I need to run an errand and it won’t start. It is the same problem as before, it won’t crank at all. I reconnect the black cable. Same thing happens. It turns right over but won’t stay running. I reconnect the red cable. Once again, all is well. I disconnect the cables and it stays running.
What the heck is going on?