Intermitent no start
 

I'm having a problem with my girlfreind's 90 legend. I just wanted to check with you guys to see if you've ran into this before. It usually takes a few seconds of cranking to get the engine to start up, sometimes it will take 3 or 4 tries to finally get it to start. Ocasionally it will start then die and I think a couple times she said it was jerking really bad when she was driving it. Every once in a while will get a check engine light. If checked and got a code for tdc sensor, but I always thought that if your tdc sensor died it couldn't run. Also in my book in perenthesis it say crank angle sensor next to tdc sesnor. Anyway I was just curious if any of you have ran into this problem, also I know the crank angle sensor is replaceable, but can you replace the tdc sensor or do you have to replace the whole distributor?