Just bought 2001 Millenia S
 

I just bought a Mazda Millenia S (2001). It was running great when I bought it and now the check engine light came on and the engine seems to be missing. It seems to be exacerbated by turning on the AC. It is not losing power. There are no heat issues. It just misses. The check engine codes at Auto Zone are P031 and P041 (catalytic system below threshhold). I don't know if this means I need a new cat or oxygen sensor. While the engine missing (what I believe to be engine missing) did happen at the same time the engine light went on, I don't know if these two things are related.

If you have had similar problems or know what I'm talking about, please reply.

Thanks,

Ryan

your codes are missing a digit. pre cat codes are P0421/P0431. an engine that is missing means you are not getting a complete combustion of fuel, and raw fuel is killing the pre cats. the missing could be cause by weak coils, or wrong plugs. it is very common that idiots dont know which spark plug to use in the 2.3, or they listen to some dumbass parts guy who recommends iridium. gap is critical in the 2.3, and NO iridium plug comes with the correct gap. if the plugs are old, then the gap may be worn too big, and you get missing, then the coils die. and they cost about 200 each. and you have 6 of them. it is also very common with this motor that if it is taken to a shop to have the plugs changed, that only the front bank gets done. it is kinda intimidating to do the rear bank, and a lot of shops just leave it, but charge you for it. i would say start with fresh sparkplugs, ngk 3741 come with the correct gap. then, as you are changing the plugs, move the rear bank(1, 3, 5) coils to the front, and front to rear. make sure you number the coils. the rear bank gets a lot more heat, and stuff back there dies quicker. also, the front bank is so easy to do, if the coils do go bad, the front bank is way easier to change. if you cannot do the work yourself, get rid of the car now, it will eat your lunch

2001 Mazda Millenia S
 

Hello Kenin: This is what I posted again. If you believe it's the plugs and wires we'll check (these however were replaced very recently), or maybe this describes the problem better... Thank you...

Hello I have a Mazda Millenia S (2001) with a 2.3L Miller Cycle Engine. The engine is missing (sounding like a rumbling diesel) when in drive and at idle. It is worse when the air conditioner is on, and it is really bad when braking to a stop (such as slowing down and gliding into a parking spot - it rum rum rumbles like the engine is going to stall).

My brother had me put it in drive and I popped the hood and held the brake while he looked at the engine. I could see it through the windshield and it POPS! like it's going to come out from under the hood.

The dealership suggests replacing left and right catalytic converters and we did replace a broken Tee Valve (this seemed to improve acceleration but did not fix the missing).

Thanks in advance guys/gals for any of your help.

Ryan

My previous post on this issue read like this: https://www.mazdaforum.com/forum/maz...lenia-s-26390/