i have a 2002 chevy trailblazer 4x4 and this is the problem it has a puttering problem it does it at constant speed and its worse when u turn on the AC and when it climbs hills, also at a stand still But it wont stall or I cant get any light to trigger . it also sounds as it is back firing out the exaust and i have it at NUMBEROUS garages and they all said yes i see when you step on it it does loose power But still they all seem to be scrating heads can anyone please let me know if You may have a clue or had the simular problem with a trailblazer .. ?? please I need all the help I can get If u want u may emal me at Gordonsgurli24@aol.com thanks again

By "puttering" do you mean the engine is misfiring?Or just NO power?I presume you have had the usual basic tune up services performed,spark plugs,spark plug wires,fuel filter,air filter,etc.Catalytic convertor can restrict exhaust flow too,when they go bad,and cause a severe lack of power.

it has a puttering problem like it wants to stall and when ur at a stop light or climbing hills or just idioling it putters and i cant get any lights or make it stall and when u step on it , it sounds as its backfiring out of the exaust .. i had a oxygen sensor replace cause it was doing it thats the puttering and i finally got check engine light on and they replaces it and it ran good for about a week and its back to the same thing it did before the oxygen sensor was replaced.. it has only 78thousand on it

It could be another bad O2 sensor,there are more than 1...like 4,......O2 sensors on your vehicle if it's the 4.3 ltr 6 cylinder.Ford's sometimes use 6....O2 sensors.And BTW...you likely diagnosed the problem yourself just knowing the vehicle history.

it was all checked and all came back good and had scope done also and nothing !! there are 2 o2 censors on trail blazers 1 in front and 1 in back of converter they said so i am lost its at another garage go figure and lets see if thee can find the problem