New DP Opinions Please

**EJOUIE** · 08-12-2015

I am getting a p0420 code for the cat. I have had the zzp dp on there for 12,000 miles and now its throwing codes. This may also be due to the fact that during those 12,000 miles I had failing LIM gaskets (felpro metal ones) which caused misfires and significant coolant burning. I do need to replace it so the question is do I go and get another ZZP dp or do I get this Walker Ultra one off of amazon.

http://www.amazon.com/Walker-54627-U...ter+direct+fit

Or this one

http://www.amazon.com/Walker-54758-D...ter+direct+fit

I am not looking into having one welded as the labor rates around here are crazy. I got quoted about $120. Add in a decent cat and now we are more than these direct fit ones.

**REDCRAPGP** · 08-12-2015

Spark plug fouler trick... Google it before you spend money on a cat!

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**EHB** · 08-12-2015

your cat isn't necessarily shot. sometimes it takes awhile before they throw a code due to the high flow design. some people get the code right after install , some take a few weeks or months , some never throw a code. i'd make sure the cat is actually bad first. are you getting any symptoms other than the code ? smelly exhaust ? loss of power ?
have you ruled out the down stream O2 sensor as the source of the code ?

**EJOUIE** · 08-12-2015

Down stream o2 is bouncing along with the upstream in voltage. 0.1 to 0.9. Seems to be reading well. Car does not seem sluggish per se but my fuel economy is significantly lower.

It did not do this before the code. Downstream was fairly steady before.

**EHB** · 08-12-2015

hmmm..the downstream o2 doesn't affect fuel mileage like the upstream does. if you shut the CEL off does it come right back on. exhaust leaks can also throw the p0420. i had a cracked front mani and didn't know it until i took the heat shield off to install a plog.

**EJOUIE** · 08-12-2015

I assume that a partly clogged cat could affect mileage, but an exhaust leak also could be it. How would I go about checking that? Where are the trouble spots to look at first?

**Scottydoggs** · 08-12-2015

the chances of the cat being clogged up in 12,000 miles is unlikely. zzp cat is hi flow too.

clear the code with a scanner, or unplug the battery for 1.2 hr or so. that will re set the pcm and clear the code. it may never come back on. or maybe in a week.

if the light comes back on, id toss a fouler on the o2 and see what happens.

**EJOUIE** · 08-12-2015

I've reset 3 times in the past week. Something is definitely up.

Which non foulers are recommended for our cars?

Also this fix seems to defeat the purpose of the downstream o2, how would I tell that the cat is bad in the future? Just gotta see if the other symptoms show?

**EHB** · 08-12-2015

the easiest way to find an exhaust leak is seafoam through the vacuum line and look to see where the smoke comes out. hey it might be a clogged cat , but to have a significant decrease in fuel mileage without the car running noticeably different at the same time just seems odd. have you ever changed the O2 SENSORS ? remember the sensors got fogged with the same crap the cat did.

**Scottydoggs** · 08-12-2015

if it was clogged up it would feel gutless and feel like it lost 50 to 100 hp.

they kinda sound like a vacuum with a full bag when on the gas hard. trying to suck, but cant. like when you put your hand over the suction tube.

**EHB** · 08-12-2015

zzp even warns that the high flow cat can throw a code. but that wouldn't make you lose fuel mileage. clear the codes again and unplug the battery like scotty says.

**EJOUIE** · 08-12-2015

I have not changed the o2 sensors. They appear to be working but they are old. Thinking I may change them because of murphys law at this point.

**EJOUIE** · 08-12-2015

So probably not clogged then. Still could be: exhaust leak, old o2 sensors, picky rear o2 sensor.

**Scottydoggs** · 08-12-2015

Originally Posted by EHB

the easiest way to find an exhaust leak is seafoam through the vacuum line and look to see where the smoke comes out. hey it might be a clogged cat , but to have a significant decrease in fuel mileage without the car running noticeably different at the same time just seems odd. have you ever changed the O2 SENSORS ? remember the sensors got fogged with the same crap the cat did.

my car dont even know wtf a rear o2 is any more. i got a up stream o2 in the bung to just seal the hole, the wire is tucked up in the heat shield to fake out inspection lol. cat code is also deleted. but even catless it passed the cat test and went "ready" its only deleted now because i can delete it. i got a hi flow cat now cause NJ wants to see a cat.

**EHB** · 08-12-2015

a front O2 not throwing a code yet can still cause you to get bad fuel mileage. replace both of them and ONLY use acdelco's. amazon has them pretty cheap. about $30-35 each. do that first...100,000 miles they should be replaced anyway. i'd also change the plugs if you haven't done that since you had problems...they to were fogged. and clean your maf while your at it...lol

**EJOUIE** · 08-12-2015

Acdelco and not Bosch?

**Scottydoggs** · 08-12-2015

get delco o2's for sure.

**EHB** · 08-12-2015

Originally Posted by EJOUIE

Acdelco and not Bosch?

NO BOSCH !!! only ac delco...lots of people have problems with bosch.

**EJOUIE** · 08-12-2015

Done. Came to just about what my father owed me so only a little out of my pocket.

If these don't fix the issue, I'm fairly certain they would fix another down the road. Car has 162,000 on it and to my knowledge the o2 sensors are stock.