Thread: Po420 help

Yes, i meant to come back and post that last night.... Both o2 sensors were replaced about 6 months ago with Bosch sensors.

I've also cleaned the throttle plate/body about every other oil change.

If i occasionally plug in scan tool.... It usually has said there is a pending po420 code.... And eventually sets the light/code on.

So there is something going on, she doesn't like.

As others have mentioned, im wondering if i just need a dealer cat.... I never had any SES lights until aftermarket cat from O'Reilly was installed.
And OE was only replaced due to a crack in mounting flex flange causing a minor leak.

Are the E3 plugs platinum? If so, pull those out and stick a normal set of NGK iridium plugs in it. These ignition systems hate plats, just in case you weren't aware.

As far as the cat, could be too high flow or low cell count and it's tripping the light. I know Walker seems to have good luck as far as a replacement cat goes, as does OEM. Not sure what brand of cat Oreilly's sells.

I would look at your ltft and stft (long and short term fuel trims) to see if you have an underlying issue such as a vacuum leak. If the fuel trims are within 5%+- while driving, then your options are to 1.) replace with a stock oem catalytic converter 2.) ignore the code 3.) have the code tuned out with hptuners 4.) blow up and/or sell your car

Good luck!

According to the receipt and comparing that p/n (20205) to OReilly website, it is a Magnaflow cat. Direct fit.

The e3.44 spark plugs per their site does not say anything about being platnium or iridium.

@fivefingerdeathpunch tell me more about this non-fouler trick.... How, what do i need and can you link to any other posts on this?
Is it permanent, if it doesn't help?

And
@wstefan20 I've seen fuel trim numbers in my scan tool before, but can you be more detailed on what to look for? As my scan tool doesn't record. But i can look at all the data stream.... Examples of good vs bad numbers please?

My scan tool is a "Launch Creader VIII"

although i think if there was a vacuum leak, there would be some kind of driveability issue, there is none... Have done the old school trick of spraying carb cleaner around intakes and gaskets and such... Looking for idle changes.... Again none found.

Per Oreilly's website:

Product Information

• Warranty: 5 Year Limited Warranty
• Unit of Measure: Each
• UPC: # 894489000442
• Hex Size (In): 5/8 Inch
• Thread Size: 14mm
• Center Electrode Design: Standard
• Thread Reach (In): 11/16 Inch
• Preset Gap (In): 0.04 Inch
• Short Style Spark Plug: No
• Resistor Plug: Yes
• Center Electrode Tip Material: Nickel
• Ground Electrode Tip Material: Nickel
• Center Electrode Core Material: Copper
• Seat: Tapered

Looks like those plugs will work for now. Check the long term fuel trim and see if it's 16.4%+ at idle in park. If so then you have a vac leak somewhere. Suspect the EGR tube and injector O-rings.

Fuel trims usually read as a percentage plus or minus to indicate rich or lean condition and normally I run plus or minus 1-2% depending on acceleration or deceleration. Anything between 5-10% won't cause a drivability issue or check engine light for fuel trims, but could cause your code.

The carb or propane trick works for large leaks but not small ones. I've got a good post on here about a diy smoke machine that works wonders, but again, only if your fuel trims are off.

Warning about the spark plug non Fowler trick. Yes, it works, but over time, water condenses around the o2 sensor and corodes it. It works for a quick fix, but not a long term solution.

Thanks for the help all!
This project will be on a short hold (hopefully short).
I hit a deer the other night.... Car still runs and drives, no injuries and it could have been much worse but visually Bambi damaged the hood, bumper and headlight.... I still need a body shop to look it over.

Just wanted to ask everyone to stay tuned.... As after this mess is over, i will get those fuel trim numbers and revisit this.

Thank you for your help.... Please stay tuned, I'm sure I will have more questions!

do they test for emissions in your state? you could have bought a tuner and tuned out the code for less than half of what you paid for an oem converter.

Originally Posted by mguzzo

did I just read that you spent $1200 for a new downpipe and converter? You could have gotten a new OEM style premium DP and cat off RockAuto for less than a third of that

...and gotten an HPT to tune and monitor the situation for peace of mind.