PO421 code and PO303

[brett02]

I am going first apologize for all of the posts about, what seems to be, the same issue. You all have helped out a lot with helping me trouble shoot this issue.

CEL came on and has these two codes, PO303 cylinder 3 misfire and PO421 I believe is the warm up cat, cat at the header.

Question is: Is the cat the same for a Protege as it is for the MP5? I am wondering because Magnaflow only lists the Protege.

Also, do you think that it would be better to just do a header and eliminate that cat, secondary cat is already gutted, if that makes a difference.

With the cylinder 3 misfire and doing all of the things mentioned on other posts, what else would cause this? I have looked into the fact that the ECM could be bad as well.

Thanks for your help in advance.

 

[TheMAN]

all the protege engine related s*** is the same as the P5

your misfire caused your cat to melt

 

[brett02]

Cool, thank you for the quick reply.I thought someone had told me that, I was just double checking. I saw a header for sale in the, obviously, for sale section. Sent a PM to them to see if they still have. Its a little cheaper than a new cat.

It's crazy how much crap I have gone through trying to get this misfire taken care of, and of course then my cat goes bad, yeah.

I did change out that EGR valve like you had suggested, man I could not get that old one cleaned good enough to look like the new one. Got good at taking it off and putting it on though.

I appreciate the info and the help boss.

 

[TheMAN]

a header is just going to make your car fail emissions and stink since you punched out the 2nd cat (which nobody does except for the 1st one)

 

[brett02]

Kansas does not have emissions, lucky me. I am planning on getting that second cat replaced with a new one. So it will smell bad? Guess I am kinda the odd man out punching the second one huh.

 

[Jamie123]

this is weird im actually having the same problem or was rather...i had the P0303 code the car had a miss and was hesitating pretty bad the cel was blinking and messed around with it and later in the day decided to replace the spark plugs and wires (i had taken my valve cover off to paint it and i think thats what caused the problems) the car has ran perfect for a 3 hour drive except for after about a hour tho it did throw a cel and it was that warm up code u have but i HAVE a header it still ran fine it just threw the code...im confused about it and came on here to look stuff up and seen your post.

 

[Jamie123]

well after looking more stuff up and also talking to my boyfriend because i have a header the oxygen is the same at both censers so the cat is not doing its job...but because i have no cat i only have a header its gonna do that for me lol
at least i can shut my cel off good luck to you you probly have a misfire and it caused your cat to go bad and thats why your throwing both codes.

 

[TheMAN]

does every one of your posts have to be one big run on that gives anyone a headache reading?

 

[brett02]

Yeah, I had plenty that seemed to go wrong. I have a list of stuff that I changed, within the last two weeks, new egr valve, wires, plugs, coils, cleaned the MAF sensor, electrical connectors, and IAC solenoid. Yep, I have been working on this thing a bit lately. So you have no cat at all? I guess technically I don't, but I plan on putting one back in on the secondary cat.

 

[Jamie123]

does every one of your posts have to be one big run on that gives anyone a headache reading?

sorry i thought people would be more concerned with what i was saying not whether i used proper punctuation or not...just dont read my posts if they give you a headache problem solved!

 

[br289165]

Comeon man be nice unless he ***** wit you like some of the idiots on here will do

does every one of your posts have to be one big run on that gives anyone a headache reading?

 

[TheMAN]

Yeah, I had plenty that seemed to go wrong. I have a list of stuff that I changed, within the last two weeks, new egr valve, wires, plugs, coils, cleaned the MAF sensor, electrical connectors, and IAC solenoid. Yep, I have been working on this thing a bit lately. So you have no cat at all? I guess technically I don't, but I plan on putting one back in on the secondary cat.

have you ever looked into a bad fuel injector? swap 3 and 4 and see if it follows it

 

[brett02]

You know someone mentioned to me maybe injectors. I will give that a shot tomorrow and let you know. Reset the ECU first of course. Thanks.

 

[slavrenz]

Comeon man be nice unless he ***** wit you like some of the idiots on here will do

You guys gotta get some thicker skin. If you're on here for any reasonable length of time, you're gonna get heckled by TheMAN. Honestly though, the run-on sentences are annoying to read and a little punctuation is not too much to ask for. Yeah, we want to help you, but if just reading through the post takes a great deal of effort, we're going to be less inclined to want to put in the effort to help.

 

[TheMAN]

sorry i thought people would be more concerned with what i was saying not whether i used proper punctuation or not...just dont read my posts if they give you a headache problem solved!

you're right... I stopped reading your post halfway through the first line of your first reply.... yes I TRIED

sorry, this place is not myspace or your sms... omgz!youdonthavelimitedspacetotypesoyoudonthavetotypeitalltogetherk!tnxc2!

making your post in a mess is downright rude, and you're just going to get a rude response or ignored at best... just like anything else in life, if you're rude to someone, they're rude back to you

so its really simple... type it all out clearly so people can easily read... then they can easily help you.... we don't expect perfect spelling, punctuation or grammar, but we expect readability... so don't come back and say anything about "grammar police", "english teacher", or "english class"

 

[brett02]

Ok, got the injectors swapped, 3 to 4, 4 to 3. CEL code was random misfire, car drove like complete crap, would die in drive at the stop light and acceleration sputtered until about 15-20 miles an hour or so.

Any ideas? Fuel injector(s) you think?

I found them on rockauto for about $30 each, thinking about overnighting them for Friday.

Oh yeah, and no PO421 code this time either.

 

[TheMAN]

sounding like injectors

if that fixes it, it's not the true solution to the problem
you need to go to the source... the fuel filter... replace it!

 

[brett02]

Should I just replace all 4 to eliminate any possibility of another fuel injector, or just the one, since it was the one on the cylinder that has been having the most misfire codes on it, cylinder 3.

Fuel filter was changed about a year and a half to two years ago, but its cheap enough, I will tackle that this weekend, so much for labor day.

Let me know if you think I should just do all four and be done with that part.

Thanks so much for your help.

 

[brett02]

Went ahead and ordered all four, why the hell not. I will get the strainer/filter, whatever they want to call it, this weekend and change it.

How much of a pain is it to change the strainer/filter?

Thanks again for your help.

 

[shadowncs]

<start flame>
How about the 2nd filter in the pump?