99 protege - P0420 code, rattling, accel issues, shifting weirdness

[mixologist03]

hi everyone,

just found this forum, and am trying to diagnose my 99 protege, which i've had for almost five years.

about two years ago, the check engine light came on with code P0420. never affected anything, it went away.

recently, the light came back. a check shows the same code.

also, fairly recently, a few interesting things have started happening.

one, when accelerating through 2.5K RPM, there's a loud metallic rattle that goes away as the car downshifts. the best way to describe the noise is as if something is hitting a moving fan blade.

once the car accelerates through 3-3.5K RPM, there's a little lag in shifting, so it feels like. sometimes, some jumping as it shifts, or hesitation.

all of this is concerning me, as i'm not really wanting to dump a ton more money into this car (already did new brakes, lots of work on various parts about a year and a half ago).

any ideas? thanks!

[Deenoe]

P0420 OBD-II Trouble Code
Technical Description

Catalyst System Efficiency Below Threshold (Bank 1)
What does that mean?

The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

At first I would of said EGR Valve.. but I thought code read P0402, not P0420.

So definitely a problem with the catalytic converter according to the read (especially that the code is triggered if A = B... so you can't really go wrong there).

[99ProtegeKV]

mixologist, i have the same problem. well similar. when i rev the engine while in park or nuetral, or accelerate and hit over like... 3.5-4.5K RPM, i hear that metal grindning sound too.. my engines a 1.6L 4 CYL, Auto, Stock. im getting a K&N Air Filter and a AEM SRI soon, idk if that will help anything, but ill try.

and how can i check if my O2 sensor is broken, i was told when my moms bf gave me the car, that it needed to be replaced, and the check engine light was on constantly, for like 2 years he drove it like that., but i brought it in for an inspection and the guy reset the car, and the check engine light isnt on anymore... how important is the Oxygen Sensor, and should i bother replacing it. idk exactly what it does.

[wolffan69]

My wife's 99 protege has the same problems that you guys have been describing. Have you figured out what the rattling was? Have you figured out what caused the P0420 code?

Thanks,
-Andy

[99ProtegeKV]

its weird. its only at 4.5 to 5k rpms that it grinds. if its over 5 it doesn't grind and when its under it doesn't grind either. I can't figure it out.