Could be a gazzillion things, but to a layman like me, my bet is on the mass airflow meter (MAF). When they go, they go as you have described - out of nowhere, with the check engine light suddenly coming on and the engine correspondently suddenly idling rough. A similar scenario can occur when the crank sensor goes, but when that particular situation happened to me, I believe the check engine light did not come on. Unfortunately, if these two parts are indeed the culprits, it's a pricey repair at the mechanic - in the $400-500 range. It'll also need a complete tune-up to go along with the repair - distributor cap, wires, plugs etc. as a matter of procedure. Also, from my experience, the MAF goes a lot sooner (150K and about 220K) than does the crank sensor (higher at about 280-300K).

As for the oxygen sensor, I've had good luck with the oxygen sensors on all my 240's - they've all been replaced as a matter of procedure, such as when the cat goes, rather than when they have caused a breakdown. But let's see what more engine knowledgeable people have to say...


1990 245 w/360K