Engine Performance problem
1997 Nissan Altima 4 cyl Two Wheel Drive Automatic 175000 miles
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Nissan dealer mechanic diagnosed head gasket as cause. $1000+ repair cost. No white smoke or leaks are experienced. Motor runs ok with plenty of power when not idling. Another local mechanic we use, at a large used parts dealer, doubts it's a blown head gasket and suggests we get thorough cleaning of injection system done prior to consider head gasket repair.

What do you make of it. Should we get injection sysyem professionally cleaned: $130. Should we consider head gasket repair and can you suggest a product?