I have a 2002 Protege5, and it has had a faint sputtering sound for about 8 months. I haven't felt it misfire until last week. I replaced the spark plugs and coils, as well as cleaned out the mass air flow. It does not idle rough, but I can still hear a sputtering sound when I accelerate.

My question: The exhaust already has a sputtering sound when idled, so could it just be my exhaust I'm hearing?

Thank you!

 

do you have any trouble codes?

 

have you had the car since new?
Did someone fart around with any catalytic converters?
Mileage?

 

It's giving me the O2 sensor code, I bought it used at 118,000 miles, and it currently sits at around 128,000 thousand miles.

 

That's a great point about the previous owner. I'll check my car for alterations.

 

READ: https://www.mazdaforum.com/forum/gen...effects-30404/

Gutting cats, although illegal, are not bad for engine. Nothing really much too worry about mechanically speaking unless you get a cel code then when you get another issue, you will never know as cel code always present.

 

the upstream o2 sensor is used to adjust the fuel trims. if the heater is bad, then it might work ok after the engine heats up. if the sensor is bad, then your fuel trims will be affected and you might get random misfires(another code). the downstream sensor just tells is the cat converter is working and has no effect on the engine. can you give us the code?

 

I'll swing it by the store today and get the code.