1994 960 full corrosion diagnostic reported
 

Greetings in this new year. Please help with information to this question. Volvo 960 was garage parked n non running for 4 years. When I parked it the motor needed decarbonizing as it would not pass NYS inspection. Car had only given me trouble total of 4 times since 1997 when purchased used. Mechanic diagnosed "it sat too long; all main lines corroded." I believe I know my car well enough so now I yield to expert forum. Is this diagnostic possible? Please help!!!

Not sure about the decarbonizing recommendation for a car that's been sitting for four years. What can happen is your gas can go stale, moisture can create rust and contamination, if the fuel in the rail evaporates, it can leave tarnish deposit and gaskets in the fuel system can harden and possibly leak. I'd drain the fuel tank (not sure where that old gas goes), put in a new fuel filter, disconnect the gas line at the rail then run the pump (you can jumper the relay) to flush out the gas lines etc. Then I'd do new plugs, wires, cap/rotor etc. Run a can or two of Techron (1 can per 8 gallons) to see if that will clean up the injectors. You didn't mention if you have a check engine light going on - but you may want to also consider cleaning the MAF, throttle body and idle air valve and inspect for any cracked vacuum lines. If any debris found its way into the injectors, they may need to be pulled can cleaned to unclog the nozzles. There are shops that will clean injectors for $10 to $20 per if need be. Finally, how did the car fail emissions? High HCs means its running rich or has a cold spark, high NOs means its running lean so that also gives some clues.

I doubt any mechanic can be sure of that, "all lines'? The problem is that it'd cost too much to have this done professionally (whatever it is, many systems have to be checked, like mt said). You can do it if you are handy and may not be all that much to handle... It all depends on what exposure the car got in four years...