Whoever changed your distributor cap and rotor shouldn't have loosened the distributor housing at all. It's not necessary to loosen any bolts when those parts are being replaced.
If he did however, then yes, your timing could be off, and it would cause hesitation problems like you describe. If you have someone with a "Timing light", then you can have them check the initial timing on your vehicle. It should be set at 6-degrees B.T.C. (Before top dead center)
Also, the trouble codes that you named are:
12= Speed sensor pulse
44= Oxygen sensor (Lean)
The speed sensor is mounted to you transmission and tells the computer how fast the car is going relative to where the throttle position is. (Accelerator peddle)
The Oxygen sensor code is telling the computer that there is a lean condition. That does NOT mean that your oxygen sensor is bad. It means that you engine is not getting enough fuel, and the oxygen sensor is reading it, and passing that information on to the computer.
The reason why your check engine light came back on, is because you replaced parts that weren't the problem.
There can be several reasons why your engine is running lean. It could be the fuel pump, fuel pressure regulator. If you have injection, then one or more injectors can be bad. If you have a carburetor, then there could be several problems with that.
It is never a good idea to replace parts and hope they do the trick. Because that hardly ever works, and only cost you money that you could've just spent at a mechanic. If you have a suspected bad part, but no money to take it to a shop, then have the part removed, take it to a parts store and ask them to check it for you. They'll usually do this for free, depending on the part.
Finally, it is very important to find out why your engine is running lean. Because when a motor isn't getting enough fuel, it will surely blow.
Sunday, January 3rd, 2010 AT 8:38 PM