The 2.5L in my 89 YJ has been backfiring for a while. When cold, it idles smooth and runs fine. When hot the idle can drop as low as about 5-600rpms, but sometimes is smooth. Sometimes it will backfire on deceleration. This is only usually if you downshift to slow down. The backfiring is pretty bad, sounds like a gunshot. There is a hesitation off idle. Typically, the rpms will drop before rising when I press the gas pedal. This is all pretty much when the engine is warm. It's not over heating. I used to smell gas fumes when it was cold. Lastly, the tail pipe is pretty black on the inside.
Where do I even start?
Carl