Cadillac Repair: Oxygen Sensor 99 STS, throttle position sensor, oxygen sensors

Question
I replaced an O2 sensor on my 99 STS about a year ago along with some vaccum hoses.  The problem then was a bogging of the engine around 2200 rpm, well the problem is back.  Could it be the same thing all over again.   I have an additional problem this time at stop lights it feels like my car is going to jump into the car in front of me because the idle goes from 600-1100 rpm.  I believe the two problems are related to each other. Any help would be appreciated.

Thanks

Jon

Answer
Hi Jon, Scanning for codes or looking at the computor data might shed some light on the problem. As you are aware there are 4 oxygen sensors on your car and the same one might not be bad this time. The throttle position sensor, egr valve, fuel pressure, restricted or shorting fuel injectors, plugs and wire or the engine computor/PCM to name a few things all need to be tested and ruled out as possable causes for the bogging. As for the jumping idle the idle speed control motor or idle air control motor might be sticking or if you replaced the battery or it went dead and then the problems surfaced then relearning the idle might get things back to normal. If you can trace the problems to an event like a prior repair or such then that would help. Otherwise I have heard of faulty computors that act up when hot, cold or when vibrated over bumps. Sounds like you might need some help from a shop with this one for diagnosis. Bill