Need Help With My Gtp

i have a 97 gtp and in the pas couple of weeks my gas milage has gone to shit. i did plugs wires etc. im wounderin if the o2 sensors are easy to get to and where they are located thanks guys.

Welcome to AF.

Is your GTP stock? O2 sensors are easy to get at and replace DIY. One (pre CAT) is located on the downpipe right after the exhaust manifolds and the post CAT sensor is located in the u-bend after the CAT convertor. Recommended to use an O2 sensor socket which has the cutout for the wiring harness. Also, use PB Blaster at the bungs/threads for easier removal.

Be sure to use the OEM spec AC Delco O2 sensors. AC Delco part numbers are:

AFS109 - Front O2 Sensor
AFS123 - Rear O2 Sensor

But Bob, doesnt the PCM only use the pre-cat O2 sensor to monitor fuel delivery and the post-cat only as a cat efficiency monitor? Then why should he replace both to help with fuel milage? Couldn't he just change the O2 sensor before the cat to help improve gas milage?

(Its funny how the weather starts getting colder we start to see more posts on bad milage)

But Bob, doesnt the PCM only use the pre-cat O2 sensor to monitor fuel delivery and the post-cat only as a cat efficiency monitor? Then why should he replace both to help with fuel milage? Couldn't he just change the O2 sensor before the cat to help improve gas milage?

(Its funny how the weather starts getting colder we start to see more posts on bad milage)

Cold weather does affect overall fuel economy and is not the best time of year to gauge whether you are getting acceptable or abnormal fuel economy unless the figures are way off. Plus too many variables and conditions involved.

My suggestion is to replace both especially if they are the originals. True the front 02 sensor is the primary O2 sensor used to help control the air/fuel mixture ratio in the closed loop mode of operation which is at idle and cruising speeds and for optimum emissions control. But why overlook the rear O2 sensor depending on the age of the car or mileage especially since it monitors CAT convertor efficiency. A bad CAT which can definitely cause adverse fuel economy can go undetected especially if the post CAT sensor is flaky. :2cents:

But this discussion at this point in time unlike the other active one concerning poor fuel economy has not evolved to that yet. But it is important for the OP to post what figures he/she is getting.