I need some advice on how to locate a miss in my engine. A quick background on the car: I bought a 1995 Mazda 626 for $700 from an old couple in my neighborhood. It has been sitting up for quite some time. I had to replace the fuel pump and alternator. I went ahead and drained the old gas and have added fuel system cleaner in the tank and have ran about half a tank out already. The motor sounds great and performs well, except when the miss occurs. It was running fine until I drove it to get new tires, about 10 miles round trip, and it developed a miss. I'm planning on replacing the fuel filter this weekend. The miss isn't a constant problem, meaning the car will idle and even drive fine at times and then the miss will come back into play. When the engine does "miss", it occurs whether It's idling or driving. I was told my problem is most likely trash in the fuel lines and will "work itself out, I just have to drive it," but I don,t like to assume any problem will just go away and often use instances like this to learn something new about whatever project I'm on. This isn't my first cheap car to fix up, but is my first mazda and the first time I've encountered a miss. I'm not a mechanic, but know enough to usually figure out the problem and go about fixing it. However, I also know when to turn to those with more knowledge than I have.

 

Just a wild guess, Audio, but adding fuel system cleaner may have broken down some surface rust that developed in the tank while the car was sitting. This could find it's way to the fuel pump and be clogging the pump's inlet/filter/sock.
In any case, with a car that's been sitting for an extended period, it's not a bad idea to drop the tank, pull the pump and blow out the rest of the lines.
You also don't mention whether the car is a 4 or 6 cyl version?