242 4.0L I6

AMC 242 I6
AMC 242 4.0L I6 – photo by CZmarlin

AMC 242 4.0L I6

Problems

All Engines

  • Squealing/chirping belt can be fixed by adjusting the idler pulley
  • The exhaust manifold may crack where the collector pipes merge, which can cause an exhaust leak while also sucking in fresh air and confusing the oxygen sensor. This can cause the engine to run rich and bog down.
  • The fuel injectors can get hot and cause the fuel to turn to vapor, which may cause the car to run rough or stall. Eventually, the injectors will push out all the vapor and start pumping fresh fuel again. This happens more frequently with old injectors, as the plastic housings can crack. Chrysler released two TSBs for this which involve:
    • Reprogramming the ECU to engage the electric fan earlier in an effort to reduce engine bay temperatures – this is largely ineffective
    • Installation of “heat sleeves” around the injectors
  • Oil leaks:
    • Rear main seal (RMS) – can be fixed easily by replacing the seal, which is accessible simply by dropping the oil pan
    • Valve cover gasket
    • Oil filter adapter
    • Oil pan gasket
  • Piston slap is unfortunately very common for this engine…but unlike most, it does not result in a quick death. In fact, the engine can live for tens of thousands of miles with slap.

Certain Vehicles

  • Engines that use the Renix fuel injection system (MY87-90): The bolts that hold the intake and exhaust manifolds to the engine can come loose and should be re-tightened

Usage