I agree with Roy. If Nestor6804 has the overhead cam 4.0 the it will require the removal of the engine to remove the heads. So well over $2300.
Also if the check engine light is flashing then find out what trouble code is related to what cylinder is missing to isolate what cylinder. If Nestor6804 has compression on all 6 cylinders within 20% of each other. Than it could be a bad plug/plugs wires or coil pack.
I really doubt that you need a valve job-I haven't heard of that being a remedy in ages..Ignition and other controls need to be in proper order first,before jumping to a mechanical repair.
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I agree with Roy. If Nestor6804 has the overhead cam 4.0 the it will require the removal of the engine to remove the heads. So well over $2300. Also if the check engine light is flashing then find out what trouble code is related to what cylinder is missing to isolate what cylinder. If Nestor6804 has compression on all 6 cylinders within 20% of each other. Than it could be a bad plug/plugs wires or coil pack.