my 1998 blazer 4x4 sputters lopes at > 60 mph. no trouble starting, idling. has 190 k on odometer and had complete tuneup at 130k which included catalytic conveter replacement along with o2 sensors. can cat clogg so soon after replacement ? have burnt 87 octane since buying her and wonder can that choke out a cat? ses light on and im going to write down codes after trip to advance auto. also new fuel pump and filter replaced less than a year ago. love my blazer and i want to drive her for many years to come. one last thing, overhead compass/ temp display quit working one day and i cant sem to find where to find fuse/relay wiring to test voltage. any help would be appreciated during these trying econpmic times. thank you

 

The octane rating has no effect on clogging a catalytic converter. However, if you engine has been running too rich or inefficiently, that can clog 'em up. Get those codes and come back here with 'em, that's the first place to start.

 

went to advance auto and scanner puts out P0325. i think my book says its knock sensor circuit as error code. now i think vehicle has 2 sensors one for each side of engine block. where are they exactly, and how do i test each of them to see which is bad? are they hard to replace ? any help would be appreciated thanks. lopes and sputters above 60 mph.

 

There is only one knock sensor and it is located behind the driver side cylinder head on the back of the block slightly more towards the center of the engine.

P0325 - Knock Sensor 1 Circuit