Have a 1993 jeep cherokee 4.0 straight 6. Was just told that the exhaust manafold has a crack in it. The trany has over 278,000 miles, but it has a new egine five years ago...is it time to get another?

check the coolant level. check thermostat for correct operation. Have a compression test done to check for head gasket or cracks . All indications are that the motor is overheating badly.

Does you engine sound like it has an exhaust leak under the hood? 89 4.0 litres were NOTORIOUS for the exh manifold cracking between #5 and # 6 cylinders. If this is the case, the O2 sensor is not seeing the proper amount of exhaust, and it will send the fuel injectors a richer condition than needed.

Usually a bad crank sensor or a bad ecu computer.

In my opinion, that inline 6 is one of the best engines manufactured. The exhaust problem in jeeps is well known. If you let it go the force of it pulling down affects the exhaust manifold. I have had one cherokee and 3 wranglers. KEEP IT. My Cherokee never left me stranded and lasted over 200,000 miles. The only thing to concentrate on is the driveline. The driveline is bullet proof for day to day usage. It has a Borg Warner transfer case and Dana rears You can abuse this driveline and not maintain it and it will not give up. Take care of it.! Change the transfer case oil, the rears and the transmissions fluid at the correct intervals and the body will fall apart before the mechanics do. This engine is based on the old AMC 257. My father had one and never changed the oil. It had 400,000 miles on it and he overheated it at least twice a year seizing the pistons and locking up the engine. He would just let it cool off, put oil in it and drive it a couple hours later. Not saying you can do that now, but it's a very good engine and the Cherokee will never leave you stranded.

first look for vacuum leaks around the manifold you could have easily misseated the intake or cracked it if you improperly tightened it

The problem you describe is an inherent design flaw of the manifold and commonly cracks on most vehicles over time. As long as the crack is not in an area where exhaust gases can damage wires or other items it can be ok to drive although it technically can cause vehicles to fail state inspection in most states

By 4th gear, you mean O/D? Did you change the converter? Also, check the brake light switch: the circut there disengages the od...if it's always open od won't work!

1994 is the same as 1997. parts are interchangeable

no it wont work.they made too many changes with them about 2 years older and id say yes but no they wont interchange

these jeeps did have a small problem with the tp sensor. i would also have the back pressure of the exhaust checked to see if you have a catalytic converter choked up.