Running lean

[builds4christ]

Hey all,

Seem to be posting a lot lately!

Got P0133/0153 and P1133/1153 with new 02 sensors and a clean maf. Also running 15-19% LTFT. The 02's are staying on the high end of the voltage range a little longer than they should, then dip down and back up pretty quickly.

This is a 08 Procharged 6.2L. I checked all piping for unmetered air and there is none. Made sure all clamps are tight.

Sprayed carb cleaner around intake, no change in rpms. PCV ports (both of them) are routed into a catch can and back into the intake tube of the procharger. As far as I can tell, they are working properly.

I'm kinda lost on what to check next, y'all. It does act funny too. Like when I keep my foot steady on the throttle, it surges a little. In park, the rpms will not stay where I'm holding my foot. It hunts.

Any advice would be appreciated!

 

[Fless]

How long have the LT fuel trims been high? I'd say to try resetting them with a scanner so it can start recalculating.

What fuel (E10, etc.) is it running, and what percentage of alcohol does the scanner show for the fuel system?

 

[builds4christ]

Thanks for the reply!

I would guess a week or two. It runs on 93 octane. I tried resetting o2s and trim data, but it didn't seem to work.

How do I check alcohol?

 

[OR VietVet]

Maybe the cats are not as efficient as should be and the downstream O2 is picking that up. Or, how old are the cats?

 

[mikez71]

Got P0133/0153 and P1133/1153 with new 02 sensors and a clean maf. Also running 15-19% LTFT. The 02's are staying on the high end of the voltage range a little longer than they should, then dip down and back up pretty quickly.

Possible the MAF is no good? I had that issue in my gen3, and cleaning the MAF with MAF spray cleaner did nothing.
Fuel trims were 15% to 25%. Didn't have codes for awhile, but ended up with P0101 a couple times.
With just a new MAF, my trims dropped to 5-10%.
I was getting more knock retard earlier on, so I wonder if I didn't have some old gas in there when I bought it.
Checking datalogs, old MAF was reporting about ~225g/sec at 1st gear redline. New MAF reports ~250g/sec.

Not sure about your O2 codes.. How is the thing tuned? Did it run better before?

Apparently, you want downstream O2's to read rich, that means the cats are working..
Unless you're super rich maybe?? (dunno, just speculating.. )

 

[Fless]

Thanks for the reply!

I would guess a week or two. It runs on 93 octane. I tried resetting o2s and trim data, but it didn't seem to work.

How do I check alcohol?

An advanced scanner can read what the ECU is calculating for alcohol.

 

[builds4christ]

I can check that. My scanner is pretty good. It's the Topdon Phoenix Lite 2. What will alcohol tell me? I've never heard of this before and it's intriguing!

@mikez71 @OR VietVet at this point, I might as well buy a new maf lol. But the downstream O2 sensors are fine. I'm it getting any codes for them. Honestly, I'm not certain they're set to report anything because it's a modded setup.

 

[mikez71]

Do you have long tube headers? Because I heard that can mess with O2 readings..
And because it's a modded/supercharged setup, I wonder if you have diffferent injectors too?

Interestingly, the factory wiring diagram specs Denso for precat and Delphi for postcat..

 

[builds4christ]

Do you have long tube headers? Because I heard that can mess with O2 readings..
And because it's a modded/supercharged setup, I wonder if you have diffferent injectors too?

Interestingly, the factory wiring diagram specs Denso for precat and Delphi for postcat..

I couldn't tell you on the injectors, unfortunately. I have to check into this kit they installed. There was some janky stuff going on for sure lol.

I bought it like this and have been working through it, part by part.

They are shorty headers, at least I think they are. They don't come down as far my long tubes on my Corvette.

 

[Fless]

I can check that. My scanner is pretty good. It's the Topdon Phoenix Lite 2. What will alcohol tell me? I've never heard of this before and it's intriguing!

@mikez71 @OR VietVet at this point, I might as well buy a new maf lol. But the downstream O2 sensors are fine. I'm it getting any codes for them. Honestly, I'm not certain they're set to report anything because it's a modded setup.

There are various mixes of ethanol in pump gas. One can find ethanol-free, E10 (up to 10% ethanol), E15 (up to 15% ethanol), etc. E85 is mostly ethanol, up to 85%, to be run in only Flex Fuel vehicles. Your pump should be labeled for the E-value, but don't confuse ethanol content with octane.

Alternative Fuels Data Center: Ethanol Fuel Basics

Running ethanol over 10 or 15% requires the fuel delivery system to significantly increase injector flow, and Flex Fuel systems generally have injectors that can deliver more fuel. Running any mix of ethanol can reduce the mpgs, and obviously the more ethanol content, the less mpgs. It does have a better octane rating than gas, so there's that. Flex fuel systems have different fuel maps to compensate for the different fuels that can be used.

 

[builds4christ]

Gotcha, mine isn't a flex fuel car as far as I can tell.

Cleaned the throttle body yesterday. Gonna give it a day or so of driving to see if it's still hunting. Getting the Delphi replacement MAF in today too.

I don't normally throw parts at things, but considering my time, the mileage, and the way the previous owners treated it, I'm just going to go ahead and replace some of these parts. May as well restart the clock on then, is my philosophy.

 

[builds4christ]

All right guys, here's an update.

It thew the same codes as before for the O2 sensors. I drove it around a little bit while trying to graph what's going on. I watched O2 sensors and long-term fuel trims.

The long-term fuel trims were acting really weird, jumping around, but since I'm not really used to watching the long-term fuel trims while I'm driving it, it could have been acting normally.

One thing kept happening that was interesting. The O2 sensors and long-term fuel trims seem to act normal when I was giving it at least 20% throttle. So during acceleration or a decent amount of RPM, everything seemed to be working well.

For instance, under those conditions the O2 sensors were cycling up and down normally. So it seems to be screwing up during idle mostly.

 

[LsHart]

Maybe the cats are not as efficient as should be and the downstream O2 is picking that up. Or, how old are the cats?

Here is a bit of info that was asked and not picked up on.

 

[LsHart]

Hey all,

Seem to be posting a lot lately!

Got P0133/0153 and P1133/1153 with new 02 sensors and a clean maf. Also running 15-19% LTFT. The 02's are staying on the high end of the voltage range a little longer than they should, then dip down and back up pretty quickly.

This is a 08 Procharged 6.2L. I checked all piping for unmetered air and there is none. Made sure all clamps are tight.

Sprayed carb cleaner around intake, no change in rpms. PCV ports (both of them) are routed into a catch can and back into the intake tube of the procharger. As far as I can tell, they are working properly.

I'm kinda lost on what to check next, y'all. It does act funny too. Like when I keep my foot steady on the throttle, it surges a little. In park, the rpms will not stay where I'm holding my foot. It hunts.

Any advice would be appreciated!

Is it programed (tuned)? And when did this start? After new add on? And to add, if computer is showing lean then that means it's compensating by dumping more fuel. So there is a lack of fuel or to much air.

 

[builds4christ]

Sorry I missed the question!

It doesn't have cats and the rear O2 sensors are off and not reporting.

Yes, it was tuned when the procharger was installed, before I purchased it.

It started happening about a week ago, but not after installing anything consequential. Most of what I've been working are things like mounts and stuff.

The only thing I am thinking of is there's a vacuum leak in a line somewhere.

I'm going to dig into it more today to troubleshoot. It's really only doing it at idle, but it could still be a number of things.

My 2000 jimmy was experiencing this and it had a leaky brake booster diaphragm. It took me a while to figure that one out, but I noticed whenever I hit the brake, the trims went to zero

 

[builds4christ]

Ok guys new info.

I found a bad seal on the map sensor. Replaced that.

Checked intake with the smoke machine. I connected the smoke to the port on the top of the intake that is usually connected to the rear driver's side PCV.

No discernable leaks.

I also changed the MAF for good measure, because it's old.

Reset fuel trims and took it for a drive. Now the LTFTs flipped to -18% from +18%. Super confused y'all.

I recorded a driving session at various rpms with the topdon. If anyone is confident and has the time to look at it, I'll put the YouTube link Here

Going to replace maf with the old one and see what happens. Any ideas?

 

[Fless]

One thing I notice is that the MAF appears to be way over-reporting. At the start of the video it looks like the engine speed is near idle but the MAF is at least double what it should read. At hot idle the MAF should report about the same amount in g/sec as the engine displacement in liters (e.g., 5.3 or whatever engine you have).

FWIW Note that short-term fuel trims reset with each ignition cycle. LTFTs have to be reset with a scanner; usually a battery disconnect WON'T reset LTFTs.

 

[donjetman]

If your oil is loaded with fuel from running rich before it will run lean for a while until the fuel is out of the oil.

Or you can just change the oil.

 

[LsHart]

Is there not a certain mileage u have to drive after resetting the trims? For it to relearn?

 

[Fless]

Is there not a certain mileage u have to drive after resetting the trims? For it to relearn?

It will start relearning the long-term trims right away, but the changes probably won't be very fast. One should be able to see it move in the right direction within a few minutes of running.

If there are fuel vapors in the crankcase and/or intake, it could take a few miles like @donjetman noted for very negative (rich) trims to move closer to zero.