P0420 code coming up(and yes I did a search)

[MustangEater8251]

Alright... been having a slight rattle in the exhaust. I was thinking maybe a little loose from where I unbolted and rebolted it back together... This unbolting process was done a good 1.5-2 feet behing the last 02 sensor never through a code, and had it uncapped for a good 2 weeks.

But this sounds slightly different then a loose exhaust would, had plenty of exhaust rattles in my old car to compare against and I tightened it down good, gave it a 2 full turns on the exhaust clamp with a 2 foot breaker bar.

Either way, I have had an ongoing problem slight stumble at the top end of a gear, around 4-5k rpms....

Which would lead me to believe it had a bad CAT, even before I got this code. But my car is at 36,500 miles, pretty damn premature for a CAT, my 94 lasted ~115k miles, and pulled nice times on it [img]smile.gif[/img] SO I sort of disregarded this as an option.

I did a search and people are throwing up explanations of O2 sensor wires cooked, EGR, and many other things... I believe its the CAT, but still new to 3.8L land so I am willing to take any and all input.


BTW... I had a problem is the code was not always constant(until now) so when it came on I drove to Advanced auto, and took the ignition off the ring, leaving the car running and locked the car up, Had the guy use his scanner, with car running picked up the codes with the motor running...

I did this because I have had the code go away when I shut off the car and it seems that the actual light has to be on, not on, then off, they cannot retrieve codes stored in the computer with their scanner.


Thank you...

-Eric

[ February 11, 2004: Message edited by: MustangEater8251 ]</p>

[RallyRed 98]

my cat went out at 43k but the car never stumbled... just a frequent rattle, like rocks in a tin can. don't be too surprised if it's your cat.

[MustangEater8251]

<blockquote>quote:</font><hr>Originally posted by RallyRed 98:
my cat went out at 43k but the car never stumbled... just a frequent rattle, like rocks in a tin can. don't be too surprised if it's your cat.<hr></blockquote>

Yeah, I am near certain of it but read some other people with same code but had problems with their o2s...

Just getting some input...

Either way if its the CAT, hope it holds together enough to get me down to south florida and back... and its not as bad as when my 3.4L CAt broke apart and completely clogged itself.

[malice10985]

My cat broke apart and completely clogged itself last month. It sounded like little rocks were rattling inside it, or something was not bolted down properly. Those symptoms are just like mine.

My computer threw a p0300 code though. Also, the engine never stumbled, it would simply run out of power. I couldn't break 65mph with my foot flat on the floor. The biggest giveaway was that my flowmaster cat back was no longer loud. It got strangely quiet. That was the dead givaway.

I wouldn't take chances with a clogged cat. Get it replaced. The dealer is required to replace it for free if your car is stock and is less than 8 years old/80,000 miles.

A clogged exhaust can destroy your whole engine relatively quickly.

Remember, Elvis pressly died of chronic constipation. Don't let your maro suffer the same fate.

[slow]

emmisions warrantys cover 7 years or 70,00 miles normally ;)

federal mandated

Ryan

[Go4broke]

I had the same code for a long time I just got rid of it by getting an O2 sim. I know it wasn't the cat for me because I had the old cat replace with a highflow cat.

[gen4]

A quick check with an IR thermo will tell if its clogged.

[navyblue2000]

my cat clogged up at ~54?k miles...i've heard of them blowing earlier too. With the way we drive our cars, especially the way you drive yours ;) , if you lean out just a little that can heat the cat too much and cause it to burn up. When the car's cool, tap the converter, see if you hear a rattle. that's all it took for me [img]smile.gif[/img]

yeah, P0420 is cat related too, fwiw

edit: by the time the car finally gave me the engine light, it would barely go to 2000 rpms...the computer had logged over 700 misfires :eek:

[ February 11, 2004: Message edited by: navyblue2000 ]</p>

[MustangEater8251]

I know its warrantied covered :cool:

Jsut have a plan to Ft. Lauderdale and doubt if I took my car in tomorrow it woudl be ready by noon friday.

It still pulls hard so I doubt its that bad...

I think I can make it throught the weekend.

but damn.... 36k on a CAT...

Wonder if that means my car was not at full potential on my 14.4 run ;) [img]tongue.gif[/img]

[PewterBird]

Do yourself a favor and make sure your cat is not clogged, if it is, get it fixed fast. Or you will be like me and the backpressure will **** up your EGR valve, and you will be 100 bucks lighter.

[MustangEater8251]

Got back from dealership...

Bad CAT... nearest replacement is in Jacksonville... so won't have it till tomorrow morning...

I planned on leaving at 12:30 in the afternoon... I'll replace it when I come home on monday maybe...


Also a stored code came up for multiple misfires... I had that once or twice but it was very rare...

on a good note it might be possible for me to run a little bit better [img]smile.gif[/img]

[malice10985]

MIne took about 100 miles before it got really bad. while you are on your trip, make sure you have some way to relieve exhaust back pressure. Perhaps bring tools to remove the aft o2 sensor or something.

[MustangEater8251]

I took it in today... hopefully it will not take all day... but at least its free [img]smile.gif[/img]

[malice10985]

<blockquote>quote:</font><hr>Originally posted by MustangEater8251:
I took it in today... hopefully it will not take all day... but at least its free [img]smile.gif[/img] <hr></blockquote>

I took mine to the dealer to get a free replacement when it went bad. The service guy said "what kind of mods do you have?" I said" intake, full exhaust, Camshaft, nitrous..." The guy cut me off and said "just go home, we won't warranty that" :(

[MustangEater8251]

<blockquote>quote:</font><hr>Originally posted by malice10985:


I took mine to the dealer to get a free replacement when it went bad. The service guy said "what kind of mods do you have?" I said" intake, full exhaust, Camshaft, nitrous..." The guy cut me off and said "just go home, we won't warranty that" :( <hr></blockquote>

Me: "I think its the cat, told him code, upper rpms, and rattle blah blah."
Service man: "Yeah sounds like the cat but if it isn't then its not covered and you have to pay a $90 diagnostic fee, but from what you said sounds like the CAT and its pretty common, it just was a steady light not a bliking light right?"
Me: "yeah it was steady, not blinking, why you think I was mistaking it for misfires,because that is waht I looked into first I thought it pretty wierd for a CAT to last 36k miles, and these cars are prone to ignition problems"
Service man: "Yeah the cats have been problematic as well, its not too uncommon for them to go out this early"
Me: "Its still under a warranty for emissions testing"
Service man: "Do you have any aftermarket parts on this car?"
Me: "Aftermarket stuff? like mods? you mean people actually race cars like these? ;)
No I don't have any aftermarket mods(now some of you may know why I am into the whole $0 modding thing [img]smile.gif[/img] )
Service Man: Alright we'll take care of it


:D