2002 Grand Cheroke Laredo 4.0L with 238,000 miles.



Original symptoms: leaking from every gasket and knocking in the block. (4 of the 6 pistions where cracked around the skirts) Honestly it ran fine besides the knock. Transmission was rebuilt 50k ago.



New parts installed: trans gasket, radiator, thermostat, water pump, pistons/rings, honed cylinders, rod bearings, lifters, rear main seal, oil pan gasket, head gasket (head was resurfaced and check by shop), valve cover gasket, timing chain, timing cover gasket, idler pully, drive belt, spark plugs, all fuel injectors, MAP, TPS, AIC.



Completed rebuild and upon first start it ran/sounded good for the first 20mins of break in. While on the first drive it started misfiring and choking for power. This is when I replaced all the fuel injectors, then the sensors on the throttle body. No change in misfire. Code appeared for cylinder 4 - compression test confirmed low compression of 90. Others were all 125-130 (cold). Black water spitting from tailpipe.



Opened it back up to inspect rockers and valve ends. Remove rockers, tapped on valves with rubber mallet, and re-tourque rockers on cylinder 4. Closed it up. Cylinder 4 shows 130!



Restart vehicle and it runs great for a few minutes, then starts running rough, sputtering, and dies. Misfires a little while holding 1500 RPMs. Afraid to keep it running so no codes at the moment. Clear/black water still spitting from tailpipe.



I have new crank and cam sensors to install next.



What am I missing? What do you think is causing the rough idle? What would you do next?