New guy from New Jersey

[no rotors]

Just want to say hello. I just bought a Mica Green '99 ES with 97k miles, 1-owner car, super clean in and out. $2,300. And yes,...It does have the Random Rough Idle and CEL! Other than that, it runs great.
The PO changed the coil, IAC valve, EGR valve, and MAS, but the random rough idle still persists. Sometimes it's bad enough to cause the engine to stall.

If there is a known cure for it, I would be EXTREMELY APPRECIATIVE if someone would clue me in!

Thanks,
Pete

[goldstar]

Welcome to the Forum.

If you're still getting the MIL have the code read.

Happy Motoring!

[no rotors]

MIL? Don't know what that means.
I did have the code read, and it's PO 171, Engine Too Lean. I know there are many possible causes for that.

After seeing the parts (above) that the PO changed, where would you suggest I look next? The downstream O2 sensor was also changed, but not the upstream one.
Coolant temp sensor?

Is there one particular thing that goes on a 3rd gen ES (1.8 engine) to cause the 171 code? Other than the random rough idle, it runs great.

Thanks,
Pete

[Mazda_Powered]

I know the 2.0 had issues like that from screws coming lose from an emissions/butterfly system in the intake manifold, and the screws would bounce around in the combustion chamber causing issues...but idk if that's the same as yours.

welcome to cp by the way! lol

[wgnths]

welcome to CP and try searching or posting in the 3rd gen section on here for help.

[goldstar]

MIL? Don't know what that means.
I did have the code read, and it's PO 171, Engine Too Lean. I know there are many possible causes for that.

Pete

MIL = malfunction indicator light. This is how it's referred to in the FSM - what some call the CEL (check engine light).

The most likely cause for P0171 (Fuel Trim System too Lean) is deterioration or failure of the front (upstream) O2 sensor.

Happy Motoring!