Have a 2001 t4r with ~280k miles. Have recently had issues with acceleration. It initially started happening when hitting about 1800 rpm on acceleration and would hesitate, as if it was towing a heavy load up a hill. I went ahead and changed the spark plugs and wires (both NGK) and the fuel filter, but the problem still existed. I put an ohm meter on the fuel injectors and they were within normal limits. Then things started going south...the RPMs would shoot up to 5k on startup and stay there. I checked the throttle cable and it was not sticking. I found a 4 pin throttle position sensor, installed it, and it corrected that problem. I went to take it for a test run (idles fine on startup) and the truck hesitates when attempting to accelerate. I heard an air leak from somewhere, got up under the vehicle, and found a hole in the weld bead where the O2 sensor mounts on the exhaust. I ordered a magnaflow from exhaust/catalytic converter and went ahead and got a new O2 sensor as well. Started it up, went to accelerate, and the same thing is happening. I am at wits end And hoping that someone on here has had the same issues before and can shed some insight.
