Car smoking when I stop at a light

I can't believe my luck. I just get my car running after a bad injector and now this problem starts. Yesterday after 45 minutes of city driving, I stopped for a light and the car started smoking. You couldn't see the car behind me because the cloud was so large. After the light changed, I drove for 15 minutes longer and no smoke! On my way home, same thing happened. I pulled into Walmart and checked under the hood and the tailpipe. I had a little smoke from tailpipe, but that stopped after 15 seconds of the car idling and was very light. Today the car ran fine. The smoke looks white or light blue, but coolent and oil levels seem fine. Could the PCV valve cause this problem or is the throtle body leaking? I have a new gasket on it and the bolts are tight.

Any sugestions?

Could also be brake fluid. Gets in through the power brake booster, also check the transmission modulator if you have one.

Thanks, it's the modulator. I pulled off the vacuum line on the modulator and trans fluid poured out. I replaced it and now I'm trying to adjust the new one so the car doesn't jerk on deceleration. I got it to stop clunking when the trans downshifts, but now it acks like someone is stepping on the gas when rolling to a stop.

You may have a Torque Converter Clutch Solenoid problem. I had a Cavalier do that a while back. Eventually the car will start dying as you stop, but will restart in park only to die when you put it in gear. I just unplugged the connector and have been driving it for about a year now. It does cost a little gas mileage.