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Overall the 4.0 V8 is a strong engine but do have a few issues. First the timing chain tensioners sometimes will crack. This can cause engine damage as the chain can jump and even break. You need to listen to any engine tap on first start cold as this is an indication of failing tensioners. This is also usually do to lack of maintenance from not changing the engine oil and filter regularly. The cylinders on the 1997-2001 engine are Nikasil lined which can wear out and cause the engine to lose compression. THis is usually caused by using a poor grade fuel over an extended period of time.