New to forum having problems with rough idle with engine code p0171
#31
11-12-2013, 05:16 PM
long reading. if they work for you, use them. they did not work for me. a set of spark plugs is cheap. not a lot wasted if you replace them and the problem persists. im not trying to convince you. im just sharing my experience. i will never use iridium again in my protege simply because the car does not like them. my engine is stock, just in case. when i had the problem, i even replaced the spark plug cables and one of the coil packs. problem did not go away. i replaced the plugs and all nice again.
It's weird they didn't work for you.
Don't know what brand you used but NGK is preferred with Mazda. 
#32
11-12-2013, 07:19 PM
reading again, i noticed your fuel trims are a bit high. STFT should be around 10% or less and LTFT at 25% says that your car is running lean. that is the reason you have that code. we can forget about the plugs for now. if you dont have any vacuum leaks or intake manifold leaks, try disconnecting the vacuum line from the fuel pressure regulator. if you can see fuel coming out of the regulator´s tube, replace it. if that is ok, then try to check the fuel line pressure to see if you have a weak fuel pump or a dirty fuel filter.
#33
11-12-2013, 07:34 PM
your fuel trims are a bit high. STFT should be about +/- 10% or lower. and LTFT at 25% means your car is running lean. i think we can forget about plugs for now. if you dont have any vacuum leaks or leaks in the intake manifold, then check the fuel pressure regulator. disconnect the vacuum line from it and check that you dont have any fuel present at the regulator´s tube. if you do, replace it. if all is good, then try to get a fuel pressure reading. if the fuel pressure is low, you will have a lean condition and the reason could be clogged fuel filters or a weak fuel pump. or a defective fuel pulsation damper. before replacing parts, make sure the purge solenoid and the solenoid that provides vacuum to the fuel regulator(forgot its name) are working properly, and that all vacuum lines are connected where they should be.
Last edited by Juanky; 11-12-2013 at 07:40 PM.
#34
11-12-2013, 09:42 PM
Hey man i appreciate the help but i solved the problem by replacing the MASS air flow sensor and motor mounts now my fuel trims are under 10% usually rough 5-7% also my car started have a rough idle again just recently and found out my timing belt tensioner was gone so just recently did a full timing belt job and car feels very smooth
#36
11-13-2013, 01:00 PM
just curious,
after replacing the MAF sensor, what is the air reading in g/s your car is having on idle? i will like to know just to have in my notes. before the replacement, this was your reading, quote:"Also MAFS at idle is reading somewhere between 2.5-3.0 g/s is that normal?"
thank you.
after replacing the MAF sensor, what is the air reading in g/s your car is having on idle? i will like to know just to have in my notes. before the replacement, this was your reading, quote:"Also MAFS at idle is reading somewhere between 2.5-3.0 g/s is that normal?"
thank you.
#39
11-17-2013, 10:18 AM
Hey man i appreciate the help but i solved the problem by replacing the MASS air flow sensor and motor mounts now my fuel trims are under 10% usually rough 5-7% also my car started have a rough idle again just recently and found out my timing belt tensioner was gone so just recently did a full timing belt job and car feels very smooth