Hi everyone, I've got a start-up issue which seems to be the opposite of others' start-up issues in the forum. Here's the deal:

I've been overhauling my 96' Jeep Cherokee Classic XJ since February, and I recently used two fuel injector cleaners for the gas tank (not at the same time). I've also used injector cleaner under the hood.

Recently, my Jeep began to act up upon warm start-ups. She starts up just fine when she's cold, but when she's warm, there are about 7-10 seconds of cranking and sputtering before she basically revs herself and then she goes back to normal. Also upon the warm start-ups, as she's sputtering, black smoke comes out of the tailpipe. She also drips a little bit of black liquid.

The black smoke etc. dissipates pretty quickly. She runs great and she idles just fine (actually much quieter than she used to). This also first started happening the same day that I changed the thermostat temp sensor, although I don't think the two things are related. (I'm dealing with AC overheating issues as well, which I believe is either the compressor, relays or high-pressure switch—but one thing at a time right?)

I'm thinking that this is largely related to gunk-build up that the fuel cleaners loosened up. She does have about 163,000 miles on her (hence the overhaul). I replaced the fuel filter yesterday hoping that would make a difference but none so far. No one else seems to have this issue, and her symptoms don't really match anything I've researched in terms of the fuel pump, injectors, valves, etc., so I'm not 100% sure where to start.

Has anyone out there have this happen?

Thanks in advance!