1996 Isuzu Trooper 6 cyl Four Wheel Drive Automatic 150256 miles
After several attempts to try to pinpoint the issue with my Trooper, I have replaced the fuel filter, replaced the battery, replaced the cat. Converter, checked all lines they appear to be solid no leaking or excessive wear, ect. I still have issues with my car, now apparently worse than before. The car now has a pick up in the idle speed to 3500 RPM and if I shift it into any gear it continues down to normal. After this if I put this in park or N, it will continue to idle at the steady 3500 RPM. What would be the issue?