Runs good then very poor on 1993 Mazda B2600

replaced fuel pressure regulater no better. New plugs and wires,no better.had fuel pressure checked was fine.also new fuel filter. Can be running just fine then begins to just sputter and stumble on power.Any ideas??????????????? Please help. Thanks Dan

Asked by for the 1993 Mazda B2600
It could be many things you have to look at your diagnosis to figure out if it fuel, spark or mechanical. To find an intermittent problem like this I "tee into" the fuel line and tape a fuel pressure gauge to the windscreen so I can monitor fuel pressure when the problem occurs, if fuel pressure falls off, or drops to zero you know your problem is fuel related, you then start tracing the fuel pump, fuel pump relay and sensors that allow for fuel pump operation. I also drive around with a timing light attached to one of the spark plug wires, when the vehicle falters I pull the trigger on the timing light and see if I have spark. If the there is no spark I check the ignition system, wiring and sensors associated with the ignition system. Intermittent problems are hard to find and your vehicle has limited diagnostic capabilities. Your Mazda has computerized controls with sensors that provide input to your fuel/ignition computer, if any sensor or wiring is bad this too could cause the problem. I have heard the Mazda Computer have problems.
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I'm thinking air intake issue. Vacuum leak. Unmetered air leak. Or double check the ignition wires for proper routing.
ck compression what was fuel pressure amont 45 to 50 psi