2002 Mazda Protege 5

[themodefanatic]

2002 Mazda Protege 5 - P0421 & P0300 OBDII CODES

HELP! I posted once before and have done everything I can think of nobody can seem to help me with problem. Trouble codes 1) P0421 - Warm up catalyst below threshold(bank 1) 2) P0300 - random/multiple cylinder misfire detected. Only happens at 70MPH. Replaced all vacuum lines . Replaced EGR Valve. Replaced plugs/wires. All new. Replaced fuel injectors (ALL 4). Had intake manifold cleaned out. Replaced Pre-cat(the one that bolts directly to the exhaust manifold. Replaced BOTH O2 sensors. Had exhaust system checked for leaks. Have taken it to multiple mechanics. No mechanic can find any other problems. Have spent endless amount of money to try and fix problem. Ready to blow the damn thing up. HHHHEEEELLLLPPPP!!!!!! I'm frigin losing my mind. After i replaced the pre-cat it ran fine for about 3 days then started to act up again. At 70MPH it kicks down no power with a few kicks of the gas pedal it kicks back in. As long as I keep it over 70MPH or under 65MPH its fine. Any help would be appreciated..

 

[winston3x]

Unfortunately the random misfire code can be caused many different things.
are you getting a flashing CEL when you lose power @ 70 mph? Looks like the only possible culprit you haven't changed is the ignition coils. They are fairly inexpnesive form NAPA or similar stores, very expensive from Mazda.

also, if you are getting misfires, that will clog up your precat so the p0300 may be your real problem and the p0421 is a result.

lastly, edit the title of your post, put the OBDII codes in there and you'll probably get more views/responses. best of luck

 

[themodefanatic]

replaced all of those to. and how do i edit the title of post. new here sorry.

 

[themodefanatic]

CEL blinks right after it kicks down.

 

[winston3x]

I had a similar problem a while back. blinking CEL as the misfires were happening, same symptoms - temporary loss of power etc.. p030x code

are you sure the mechanics installed new ignition coils along with the new plugs and wires? new coils fixed my problem, although now a year later my precat is dead - getting the p0421.

like I said, random misfires could be caused by lots of things, and by list above it seems like most of them have been replaced, hopefully some one else can shed some light.

as for changing the thread title - hit the edit button on your original post, then click the "go advanced", you should see where to change the title.

 

[P.O.E.T.]

* The catalytic converter is no longer functioning properly
* An oxygen sensor is not reading (functioning) properly
* A sparkplug is fouled up