I'm new at this and did look through some other posts and didn't find the same troubles. I have a '98 Park Ave. Ultra and the SES light is on.AutoZone said it was aSpeed Sensor with codes PO503 and PO502. I replaced the one on the transmission but the problem still occurs: #1 - when the car is in park and I rev the engine, at about 4,000 rpm's it gets choppie and the rpms stop increasing. #2 - when I'm driving down the road, the car does not shift gears smoothly. It is as if it is being dropped into 2nd and 3rd. It will also stall after leaving a light at about 15 to 20 mph. I have put a new Speed Sensor on it twice both from AutoZone. I have also put a throttle Position Sensor on as well. The Speedometer jumps around but the rpm's stay the same, unless it drops into gear then the rpms jump.


Any help would be appreciated. Looking to get around the repair shop run arounds. As well have had no luck with some in my area. Thank You in advance.