Hello;
Here is the situation. I have a 97 2.5 millena, the engine was replaced 2 years ago so new engine has only around 20k if that. I just purchased the car and the problems Im having were existent when I got it. I had a mechanic do several test, diagnostics and troubleshooting with little or no luck. The codes that are coming up are Cylinder 1 misfire and P0147 (O2 sensor code). The actual physical problems I am undergoing are mainly related to power and accelerating. Car starts great, idles slightly rough, if you rev engine in park it will cut out and backfire. When driving it will hardly accelerate, if I lightly tap gas it helps a little, once making it up around 40mph it will jerk and jump a little and sometimes kick in and accelerate fine to 60-70mph but you can still fill it jerking/missing while maintaining a set speed on hwy. If I floor the gas it completely bogs down and backfires loudly.

Here are the things we have gone over and tried to diagnose with no fix yet.
Compression in all cylinders perfect
Changed spark plugs
Changed Distributer
Changed wires
Took off exhaust and gutted CC (due to it being entirely plugged) and reinstalled exhaust (I forgot to mention that on one drive, we stopped car and CC was burning red color, revved engine and a big chunk of flaming hot metal came flying out of tail pipe! This is then why we gutted CC.)
Cleaned entire Throttle Body
Checked most sensors by unplugging and running car to see if any changes occurred
lastly we tore apart everything to get to timing belt and see if it had possibly jumped timing and the timing was perfect! (we were sure this was the issue causing the misfire and acceleration problems)

If I think of anything else we checked, Ill post, but this is all I can remember right now.

Please please please help! I can only hope this is something simple that we just havent caught... hoping its not a computer going bad .... any and all help or suggestions gladly appreciated. thanks

 

When you cleaned the throttle body did you look at/clean your EGR?

It wouldn't explain all of your symptoms, but it could be part of the problem.

EDIT: One thing, my old 626 used to act very similiarly, and it was always the ignition wires and the plugs. I know you said you replaced them, but that is ALWAYS what mine did when those went bad. Not saying thats whats wrong, cuz you checked it, but thats my experience. Sometimes the spark plug leads are cheap, and the claw that grasps the top of the plug can break off when you check em... That happened to me once, and the car barely ran. The backfires, in that case, would be cuased by a shorted connection, as the gas would buildup unburned and then all get ignited at once when the spark does actually go off.

Food for thought. Sorry I couldn't be more help, but no one else responded yet, so I thought I'd give it a go.

 

I was told in another forum it sounds like a bad injector problem... so that will be the next diagnostic method I check...

I thought this was the mazda forum, but no one seems to have any idea what miight be causing this problem??

thanks anyways.
it was worth a try i suppose : )

happy new year to all

 

if you do a SEARCH in the millenia forum in the upper right corner,im sure you will find more info than you can take in.alot of the problems on the millenia have come up time and time again over the past 10 years.try the search if no response comes up.what ive encountered is a problem cant be worked out over the internet,you have to be there,at least i do.i dont like telling soomeone to do something if im not sure what the problem is.you never know what level of experience the person has. happy new year to all the mazda lovers out there