Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
BACK AGAIN--PROBLEM WITH 1989 FORD RANGER 2.9-- "OBD 1" DIAGNOSTIC SYSTEM. DOGS DOWN WHEN ACCELERATING--RUNS FINE -STARTS FINE- NO ENGINE LIGHT--NO CODES. REPLACED MAP SENSOR -- RAN GREAT FOR 2 WEEKS-- BUT SLOWLY REGRESSED BACK TO NOT ACCELERATING AND SHIFTING HARD. (AUTOMATIC). ONLY 92000 MILES --ALREADY REPLACED DISTRIBUTOR MODULE--MAP- FUEL PUMP PRESSURE GOOD. TOP SPEED 50 MPH .
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"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.