A couple of times when I was able to get it going it seemed to be grinding gears, but I had the car checked out by a transmission specialist and they said it was good. I also brought it to a mechanic who changed the coil ($200), then changed the fuel filter, air filter, spark plugs and wires, plus the PCV valve – basically a tune-up for $400. They also did say that the air mass flow sensor was at 3.3 grams, which my regular mechanic took a guess at being a possible problem, but he didn’t want to be guessing and just replacing parts. Can you help?

Mark Schelkly,

Waterford, Conn.

Mark, usually an intermittent drive-ability problem such as this is devilishly difficult to solve, but your excellent description of the condition and sequence of events makes this a snap. The fault is in the transmission – a faulty torque converter clutch solenoid.

General Motors mass air flow sensors of that vintage (related to engine management) were prone to intermittent and serious hiccups under certain temperature and vibration conditions. But it’s the consistent stalling as you place the transmission in gear that is the smoking gun.

The 3.3 grams per second of airflow is right on the money for the MAF. Had this sensor been the fault, the scan tool reading would have momentarily jumped to double or triple digits as the car was stalling.

To enhance fuel economy, a majority of vehicles employ a torque converter clutch (TCC). Torque converters let some slippage occur between the engine and transmission, to allow the vehicle to come to a stop while in gear, and to enhance low- to mid-range torque.

While a marvelous component, the torque converter’s slippage is unnecessary at higher vehicle speeds, wasting fuel and contributing to transmission heating.

A TCC-equipped vehicle uses a clutch, directed by hydraulic pressure within the converter, controlled by an electric solenoid, to lock the turbine and impeller, during warmed-up, light-load, higher-speed operation.

I believe your TCC solenoid is intermittently sticking in the applied position.

Remember your first time learning to drive a vehicle with a clutch, when you forgot to disengage it when coming to a stop – bang, bang, clunk, clunk. When the engine dies, it’s the same thing.

Fortunately, renewing the TCC solenoid requires only minor transmission surgery, and does not require transmission removal.

To verify my prognosis, try driving the Century for a few days with the transmission’s electrical connector disconnected. If the TCC can’t engage, it won’t stick. This also can buy you a little time to make arrangements for the repair.

Brad Bergholdt teaches automotive technology at Evergreen Valley College in San Jose, Calif.