Bought a really nice 99 Cherokee a while back on the cheap knowing the engine was blown. Found a newer 4.0 engine that was supposedly out of a grand Cherokee with about 60 k on it. Fuel rack wouldn't wire or connect to the harness or fuel line so we ended up putting all the old engine parts on the new block. Car starts and runs but seems to be missing. Stalls if you take foot off the accelerator. Won't restart after engine warms up. Replaced throttle position sensor with one from autozone that looked similar but not identical. Don't really know for sure what year and model this engine came out of which makes parts n procurement challenging. Visibly checked harness wiring and although stiff all wires looked ok. Changed plugs and distributor wires with new ones. Anyone have any ideas?