The head gasket may seep oil externally. An updated head gasket is available that should correct this concern.
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Most reported 1990 Jeep Comanche problems
Exhaust manifolds commonly crack where the pipes are welded; the manifolds should be replaced.
The throttle body may accumulate an oily, black residue in the bore and on the throttle plate causing hard starting or possibly stalling when coming to a stop. The throttle body should be cleaned during regular maintenance but do not spray cleaners directly on or at the throttle position sensor (TPS) as this can damage the sensor.
The outer exhaust manifold studs can break and cause exhaust leaks, commonly noted as a ticking type noise. The outer studs, clamps, and nuts will need to be replaced and are now being tightened to a reduced torque value (20 Nm/180 in lbs).
Leaks at the front and/or rear differential pinion seal and from the transfer case are common. Leakage from the transfer case normally occurs at the case-mating surfaces and require removal of the transfer case to reseal.