The Check engine light on my 1990 Volvo 240 DL, automatic, 186,000 miles came on last week. The computer code, 1-2-1 indicated there is a fault in signal for air mass meter. The car started stalling at idle.
It was time for a tune up so I replaced the plugs, rotor, distributor cap, flame arrestor, and air filter. The problem didn't go away. In fact, the problem got worse after the tune up.... especially after the air filter was replaced. I have checked all of the vaccum hoses visually and do not see any cracks, and have cut a few of them to refresh the ends. Have also checked the clamps to be sure I haven't missed one.
One other problem was indicated by the computer. 2-3-1 Fuel system compensating for rich or lean mixture at cruise. After 45,000 miles the plugs were a little white, but not really burned up. I don't know if the two problems are connected or not.
Any suggestions on how to trouble shoot this problem? Thanks for any suggestions. Mike