Okay, here we go...
'99 XJ, 4.0, Auto, NP242, 280K miles, big battery & ground cables, but mostly stock with a mild lift & 31s.
Reman AW4 a couple months ago, which by the end involved a new battery as well, after a weird grounding issue killed the Red Top I had before.
Engine is a reman 4.0 installed 4 years ago, and now with about 71K on it.
Started with a rough idle a while ago, CEL but no codes, tried with my brother-in-law's much more powerful scanner, and it didn't come up with anything either. Rough idle seemed to work itself out after a couple weeks, then the CEL went away for a few days, then back, then gone, lather, rinse, repeat.
Replaced the TPS & crank sensor with MOPAR parts, cleaned & checked connections, checked grounds, O2 sensors replaced (Bosch) just because.
CEL finally went away beginning of last week, then Friday night battery was dead when I was trying to leave work. Starting it up with my little jump box took forever, because it would run a few seconds then quit. Thought it was the SKIM/Sentry system, because that's been an intermittent issue previously, but unlike those instances, if I kept giving it gas, it would keep running. As soon as I took my foot off though, it would quit again. Finally managed to get it started and drive away, and it still kept trying to die on me anytime I came to a stop. By the time I made it the 10 miles home, it was running a little better, and I could see the voltmeter was slowly climbing back toward 14, whereas at first it was around 11.5-12.
Got in the driveway & got to work again. Quickly found another bad connection, this time the positive lead for the headlight relay upgrade I did a few years ago. Got it situated, pulled the battery to charge, and left it overnight. Next day, I pulled the battery tray to better inspect wiring. Found one of my big cables had been routed under the battery tray at some point (it wasn't like that when I replaced them) and it's got a pretty significant crimp in the cable now, but no exposed wire. Rerouted it, checked all my other connections again, got under the dash to check what connections I could see there too, made sure the SKIM/Sentry wasn't loose or disconnecting either just in case. Popped the battery back in, started up immediately.
Took it to O'reilly's and asked them to check the battery & alternator, and both came back fine. All this week it's been starting just fine, but still idles rough sometimes, CEL is intermittently back (still no codes...) and when coming to a stop the RPMs sometimes drop like it's about to stall, then it pops back to just over 1000 for a moment and levels off around 700-750.
Then this morning, fast clicks and no crank. Jump box worked, but died if I took my foot off the gas. Got it running enough for me to make it to work after about 5 minutes, and it died twice on the way, both times after coming to a stop & putting it in neutral. Realized it wouldn't die but would drop the RPMs & pop back if I kept it in drive, unlike years ago when a bad alternator kept stalling me out if I wasn't in neutral.
Holy crap, y'all. Where do I look next?
-alopeks