Persistent P0420 and P0430

[MrBishop]

You can run an oiled filter on an LS with stock tuning tables just fine. There’s plenty here who do that. There’s also plenty here who remove the entire resonance chamber/ intake tube and install a cheap CAI with an even cheaper oiled filter with a stock tune with zero issues. There’s nothing needed to change in the tables to accommodate either one.

Depends. Look at your fuel trims before and after. My 3 engineering degrees and 22 years at GM tuning those tables and doing air flow test on filters disagree with you. I did MOPAR's too by the way. It works on theirs because they haven't figured out how to use a MAF sensor yet and still use speed density.

Do you think the air under hood is hotter or colder than the air in front of the vehicle?

This what the first go round for the 55 Chevy looked like. Car would not start with this set up until I modified the air tables, but it would have been a one off cal for this filter.


The next version, with modified air tables!



What else is different?

 

[MrBishop]

I would put a paper AC air filter in the car....

If it flows more or less than the one it came with, the table, and your fuel trims will be off even with paper. With oiled, when you clean and over oil it, you get oil on the MAF and throw it way out.
When you use one of GM's (or anyone's that requires you mount the MAF) 'cold' air kits, where should you mount the MAF?

 

[Rocket Man]

Depends. Look at your fuel trims before and after. My 3 engineering degrees and 22 years at GM tuning those tables and doing air flow test on filters disagree with you. I did MOPAR's too by the way. It works on theirs because they haven't figured out how to use a MAF sensor yet and still use speed density.

Do you think the air under hood is hotter or colder than the air in front of the vehicle?

This what the first go round for the 55 Chevy looked like. Car would not start with this set up until I modified the air tables, but it would have been a one off cal for this filter.
View attachment 366115

The next version, with modified air tables!

View attachment 366116

What else is different?

I stand by what I said. If you want to puff your chest and argue I’m not interested. Clean looking engine bay btw but I’ve seen better.

 

[BG1988]

Hello All,

I’ve been searching forever it feels with no luck. I bought a used 07 Tahoe with a flex fuel 5.3. 165k miles. Decent shape but as I look into it more, maintenance was sub par. It had P0430 and a bunch of EVAP codes when I got it. Replaced the cats since it was rattling. 4 new GM O2 sensors. Cleaned the throttle body, new MAP and MAF sensors, new thermostat (was sticking), fluids etc. Runs fine until P0420 and P0430 codes pop then it runs like crap. Clear the codes and back running fine. When the codes pop it’s the same type of driving; slow speed coming to a stop in a parking lot. Feels like the converter is staying locked up and wants to die. Transmission doesn’t seem to be an issue; I think. Freeze data shows negative long term fuel trims between -6 and -10 usually at between 515 and 530 RPM at 0 MPH. Tried the spacer fix and no difference. Plugs have shown no evidence of coolant or other issues that I can see. Decided to pull the injectors and clean them. A couple of them were pretty crappy but in the end all had good spray patterns. When watching live data the long term fuel trims at cruise speeds are in the high negatives. Ranging from -12 to -18 on both sides. Post cat O2 readings are in the .09 to .1 range, which show lean (correct?). You can now feel a really significant surge. Acceleration is just fine though. Checked fuel pressure at idle and it’s 55. I read one post that leads me to look closer at the fuel pump assembly but not looking to throw more parts at it if I don’t have to. Any other ideas for things to check? Thanks.

is any other codes present?

i have gotten both codes before but something else was causing it.. the cats are ok and passed smog NO CEL for them in the last 12k miles

Negative fuel trims suggest a restriction in the intake.. clogged air filter? debris in the intake tube(before the filter?) bad/ dirty MAF???

0.9-1 means it's running rich , negative deducting fuel , possibly leaking injectors

 

[MrBishop]

I stand by what I said. If you want to puff your chest and argue I’m not interested. Clean looking engine bay btw but I’ve seen better.

It was purposely built the way it was for a reason you wouldn't understand. Hard to hear when your head is in the sand. Instead of spending millions of dollars doing research and testing, I'll just call you, ROFLMAO.

 

[MrBishop]

FNG lols

Another ostrich

 

[OldEngineer]

Well didn’t don’t any leaks in the intake system. Hooked up a smoke machine and the only place any smoke ever trickled out was the air filter. Nothing from the intake or the piping. Drove around and fuel trims were between -18 and -21. I reset the trims and it goes right back. Not seeing anything on live data to justify it pulling so much fuel out. MAF seems to be correct and adjust for throttle position. The one thing I couldn’t figure out was the PSI reading on the MAP. Is it supposed to be positive? Is it in relation to the barometric pressure value? I need to research this. At idle it’s around 5.5 psi and goes up with speed. But when I get on it the value still goes up. I would expect it to be high at cruise and a little lower at idle. But I also would expect it to drop when I get on it. No? Frustrating. Don’t want to burn a hole in a piston. Where to next? Thanks all.

Your last message was in Feb, 2022.

Any success?

Still getting the same error codes?

 

[5StarCustmSolutns]

55 psi at idle seems pretty high

Mine run same range as OP's?

Have you replaced the intake gaskets?

Do you have any exhaust leaks around the manifolds or at the connection between the manifolds and y-pipe?

I do have a broken bolt head on #8 manifold. No visible sign of leak on head. Could this be contributing to a rich run condition? I've propane tested the intake area three times and found nothing, smoke tested the inward side twice and found an either. Just about have myself convinced I have an intake leak that only manifests when the engine lifts/torques under a cell load??

Explain how it takes an electrical signal and converts to an airflow value.

More air flow lowers temp of MAF sensor wires and vice versa?
Never would I try and tell someone w/your amount of experience on any subject what was right and wrong about that subject, but I've been having these same rich running neg LTFT for 24 months now. Purchased the truck 8 yrs and 2 days ago. Installed and oiled K&N 7yrs 11mos ago. In fall of '20 I removed entire stock air intake system and built the DIY in the attached pics thinking it might fix the prob....which it did not. Exact same FT's, low mpg and ill sounding cold weather starts. Just my personal experience

I stand by what I said. If you want to puff your chest and argue I’m not interested. Clean looking engine bay btw but I’ve seen better.

see above post/photos




***There is one thing (Fuel Alcohol Percentage) I didn't see elaborated on in this thread that I believe to be the cause of my issue. When scrutineering through my live data trying to fig this out, I noticed that my FA% was/is always 60% or higher. 61%, 67%, 73%, 81%, even when putting 4-5 gal of E-0. Last summer I ran 3 straight tanks of E-0 gasoline and reset my FT's and my FA% at first fill-up and EVERYTHING went back to normal for the duration of that gas. Within 2min of starting truck after switching back to 87 octane everything went right back to rich??
Sorry for long-winded attempt to revive a thread that looks to have had potential to help me with something I haven't been able to figure out.

Thanks you all in advance

 

[B-train]

Is this a flex fuel truck? If so, I wonder if the fuel sensor has failed. If it thinks there is that much alcohol in there, it's going to dump in extra fuel trying to keep 14.7:1 ratio. I know when I ran a tank of e-85 in my 2008 denali (non-flex) it ran like a champ but I got lean bank codes after a number of miles due to it not being able to satisfy the fuel rate needed. No lasting damage as far as I can tell.

As a test, I wonder how it would behave with a tank of e85, or a higher blend to get to the 60% mark it thinks its seeing. Just a thought

 

[Fless]

Mine run same range as OP's?

I do have a broken bolt head on #8 manifold. No visible sign of leak on head. Could this be contributing to a rich run condition? I've propane tested the intake area three times and found nothing, smoke tested the inward side twice and found an either. Just about have myself convinced I have an intake leak that only manifests when the engine lifts/torques under a cell load??



More air flow lowers temp of MAF sensor wires and vice versa?
Never would I try and tell someone w/your amount of experience on any subject what was right and wrong about that subject, but I've been having these same rich running neg LTFT for 24 months now. Purchased the truck 8 yrs and 2 days ago. Installed and oiled K&N 7yrs 11mos ago. In fall of '20 I removed entire stock air intake system and built the DIY in the attached pics thinking it might fix the prob....which it did not. Exact same FT's, low mpg and ill sounding cold weather starts. Just my personal experience

see above post/photos




***There is one thing (Fuel Alcohol Percentage) I didn't see elaborated on in this thread that I believe to be the cause of my issue. When scrutineering through my live data trying to fig this out, I noticed that my FA% was/is always 60% or higher. 61%, 67%, 73%, 81%, even when putting 4-5 gal of E-0. Last summer I ran 3 straight tanks of E-0 gasoline and reset my FT's and my FA% at first fill-up and EVERYTHING went back to normal for the duration of that gas. Within 2min of starting truck after switching back to 87 octane everything went right back to rich??
Sorry for long-winded attempt to revive a thread that looks to have had potential to help me with something I haven't been able to figure out.

Thanks you all in advance

If this is about the 2011 truck in your signature, it has NO physical flex fuel sensor unless someone added one. It's all done by the PCM/ECM calculations.

If you know for certain that the actual alcohol percentage is low, reset the long term fuel trims and reset the alcohol percentage.