Uhrlto

I'm not even sure how to describe what may have caused this problem, right now my Z will not start, its a 1993 NA 300zx. Several night ago I moved the car from the driveway into the garage as it was going to snow. It was very cold outside and the Z had been in the driveway for two nights in 12 degree weather. I started the engine which turned right over, went into drive and pulled into the garage and shut the engine off, a total of 20 or 30 seconds of running. Even after the key was off and out the engine continued to run for like 10 seconds before it quit with a whoosh sound. I thought that was very odd but I was really tired and cold and forgot about it. Several days went by I went out this last evening and the car would not start. The stater turns the engine over no problem but it will not fire up. I did some checks and this is what I can report. First of all the timing belt is not broken, I pulled a few bolts and can see the belt going around as I crank the engine. second I am getting a spark, I pulled number two coil and plug, grounded them out and got a spark. I can hear the fuel pump going and it sounds like the injectors are spraying fuel and I can smell a little gas. I checked the ecu. initially I got a 21 code and a 34. I cleared the codes and tried cranking the engine again and now I'm getting a 55. I'm stumped, and need help as I cant afford to take this to a shop right now. I've dome a visual inspection of the connectors and they all look good and tight. Can anyone lend a suggestion as to whats wrong. I have never had a bit of trouble with my Z until that cold night I ran it for less then 30 sec and shut it off. Thanks very much

Tony

Edit: 1\10\2013 Well I don't know what happened but now the car is starting again. I went out the other day and slammed my foot to the floor on the accelerator and just held it as I cranked the engine. After what seemed like a long time it finally kicked over with a lot of smoke out the back. I held the idle up and after about a minute or two of warming up it ran fine. It continued to start all day long with no trouble. and started up intermediately this morning cold. totally do not know what happened, but I'm glad to know I don't have to take it to the shop.