I have a 1992 mazda b2600i SE5, and on my way to work today, it started acting really weird. It was running fine for the first 5-10 minutes of the drive, then it started sputtering really bad and backfiring a lot. The thing that's throwing me off about it, is that it stops if I punch it. I know there's something wrong with the exhaust, but I don't know if that's the particular problem. (It's poorly rigged up where the manifold meets the cat converter) I would appreciate any help or insight in this. Thanks [8D]

Oh yeah, I forgot to put that now if I start it, and just let it sit there and idle, it dies out after a few minutes. And I have a new ECU in it, so I don't think it's that.

 

I would think by these symptoms that there is a fuel pump problem. Have you replaced the fuel filter any time recently? When the engine is running very lean, it will start backfiring along with no power and running erratic.

 

I had a similar problem awhile back. I have a '91 2600i and it would warm up ok, then start missing, then die. I got to poking around and found that the bolts that hold the distributor in place had loosened up, and my timing was off. All I had to do was reset it and tighten the bolts. It may not be the same problem for you, but it's quick, easy, and cheap to check.