2008 Escalade P0455, P0172 & P0175, pulling my hair out.

[93M6Formula]

With LTFTs like that I'd say you have a massive vacuum leak. Check the intake and intake gaskets. Get a spray bottle and watch the trims or O2 sensor graph as you spray water around the intake connections and gaskets.

Wouldn't that cause a lean condition though? I thought about replacing the intake itself since this EVAP issues showed up after the valve issue and I can't find a problem elsewhere, and I used this intake on the 6.0 also. I don't know if debris may have poked a hole somewhere in the intake?

 

[Fless]

I had a thought -- believe it or not -- early today, showing that the coffee is working. Have you looked at the fuel ethanol content PID to see if the computer thinks there is more or less ethanol in the gas? Theoretically if you're not running any extra ethanol (over 10%) the computer might be confused about it. SWAG but something to check.

 

[93M6Formula]

Is it running the original carbon canister full of those wonderful carbon pellets?

I'm not sure on that honestly.

 

[93M6Formula]

I had a thought -- believe it or not -- early today, showing that the coffee is working. Have you looked at the fuel ethanol content PID to see if the computer thinks there is more or less ethanol in the gas? Theoretically if you're not running any extra ethanol (over 10%) the computer might be confused about it. SWAG but something to check.

I attempted to do this but apparently 6.2 powered rigs don't have a flex sensor. I thought the exact same thing and unfortunately it doesn't exist.

 

[93M6Formula]

This pretty much pinpoints it to a faulty sensor or actuator or the circuit connecting it. Do you have a way to monitor the VVT cam phaser (probably CMP), MAF, MAP, TAC and TPS to compare them all?

I do but everything seemed normal from what I was reading. Had it on a snap on scanner and HP tuners.

 

[93M6Formula]

It's the opposite -- the codes showed that the PCM was taking away fuel (negative trims) because the O2 sensors were saying it's too rich. With the LTFTs reset to zero, and the STFTs within 5%, there shouldn't be any rich codes. That is, unless the STFTs start going way negative again.

EDIT: so what is the remaining issue, hard starting?

Hard hot starts and low on power is the main issue. LTFTs are WAY negative and get worse the more miles I have on an oil change i've noticed too. Right now it sounds like it has a mild cam when you start it cold. I just cannot figure out what is making it run rich, and I assume this is what causes the hard start is because its just dumping fuel when it shouldn't be.

 

[Doubeleive]

Common Problems That Trigger the P0455 Code​

• Missing fuel cap
• Defective or damaged fuel cap
• Distorted or damaged Fuel Tank Filler Neck
• Torn or punctured Evaporative system hose(s)
• Defective Fuel Tank Sending Unit gasket or seal
• Split or damaged Carbon Canister
• Defective Evaporative Vent Valve and/or Evaporative Purge Valve
• Defective or damaged fuel tank
• Defective Fuel Tank Pressure Sensor

 

[Geotrash]

I attempted to do this but apparently 6.2 powered rigs don't have a flex sensor. I thought the exact same thing and unfortunately it doesn't exist.

It's typically a calculation based on input from the O2 sensors. I am 100% sure that the flex fuel engines like the L94 work this way, but only 80% sure that the non flex fuel L92 does. I own both. Lol.

 

[Fless]

It's typically a calculation based on input from the O2 sensors. I am 100% sure that the flex fuel engines like the L94 work this way, but only 80% sure that the non flex fuel L92 does. I own both. Lol.

Right, if it calculated ethanol at all it's a virtual sensor, not physical. I think the last physical sensors were either 2004 or 2005 (maybe as late as 2006, but not after that).

 

[petethepug]

Replace the carbon canister if your not sure. The clip below @ the 3min mark shows what gets into your fuel system. Amazon had the best price as well as free shipping for prime.

Is it running the original carbon canister full of those wonderful carbon pellets?

I'm not sure on that honestly.

 

[Fless]

Would like to see the freeze frame data if it's available.

 

[93M6Formula]

So that EVAP code hasn't come on for awhile now and I checked the canister and it seems just fine, never had issues filling up.

But this thing is just so hit and miss right now and it's so frustrating. So I replaced the MAF just to see and nothing changed of course. Yesterday morning I started it, and it just ran like garbage right off the bat, chugging and loping like it has a small cam and eventually kind of smoothed out but the FTs were still around -15 for both banks. Went to town, it sat for an hour, did it's typical hard start crap and was just running terrible and no power. Later on in the day, I went and beat on the thing and came back and the FTs were more like -5 and it was running a little better and had power. Still started hard when hot like usual. I seriously have no idea where to go from here, those rich codes are so generic so it could be literally anything, and that's frustrating.

 

[93M6Formula]

These finally popped up again when it was running like trash in the morning.

 

[93M6Formula]

First pic is what it was doing when running terrible. Second is after I went and flogged on it.

 

[Geotrash]

Did you *swap* the O2 sensors or replace them with new? I'm with @Snowbound and suspect either plugged cats or weak O2 sensors.

 

[Doubeleive]

if it were me, I might start taking a hard look at the wiring, grounds, ecm/pcm, fuse box.

 

[B-train]

You me me mentioned the EVAP system. Are you able to see if there is a pressure change in the tank from cold start to hot restart? I had the vent solenoid stick open on my 08 with the 6.2L and hot restarts were sluggish, fuel economy went in the crapper as well. Put on new OEM solenoid and has been good since

Since the motor was in/out, are you sure all the vacuum lines are connected and not cracked or dry rotted?

The only other thing I can think of is maybe the fuel pump and/or the control module is getting flakey. I had a 2009 Denali that started stumbling and almost stalling out in 107F Temps. I filled with cool gas and then got on the highway for air movement and it seems to clear up. Inspection after the trip showed grounding issues at weird places (seats, air compressor). Maybe do a voltage drop test and see if you have a poor ground possibly.

 

[93M6Formula]

Did you *swap* the O2 sensors or replace them with new? I'm with @Snowbound and suspect either plugged cats or weak O2 sensors.

I only swapped the bank 2 sensor 1 O2 but nothing changed and they seem to be reading like they should.

 

[93M6Formula]

if it were me, I might start taking a hard look at the wiring, grounds, ecm/pcm, fuse box.

This is what i'm afraid it's coming down to. Literally nothing about this whole thing makes sense, because besides the fuel trims being all over the place, all other sensors seem to be doing what they're supposed to. Something during the engine swap happened and I have no idea what. With that said, this thing was from chicago before I got it and lived in the salt, I had to replace stupid things like the power steering pump, alternator, starter, accessory bracket, and even the manifolds because of corrosion, so it worries me that some wiring may be bad somewhere but I have no clue what as no codes for any sensor are popping up.

However the other day with that thought in mind, I checked the grounds for the coils and I believe the crank sensor on the lower end of the block, it was clearly corroded and the corrosion went up about 8 inches, so I cut that all out and replaced it, of course nothing changed though... And the grounds on the passenger head are clean also.

 

[93M6Formula]

You me me mentioned the EVAP system. Are you able to see if there is a pressure change in the tank from cold start to hot restart? I had the vent solenoid stick open on my 08 with the 6.2L and hot restarts were sluggish, fuel economy went in the crapper as well. Put on new OEM solenoid and has been good since

Since the motor was in/out, are you sure all the vacuum lines are connected and not cracked or dry rotted?

The only other thing I can think of is maybe the fuel pump and/or the control module is getting flakey. I had a 2009 Denali that started stumbling and almost stalling out in 107F Temps. I filled with cool gas and then got on the highway for air movement and it seems to clear up. Inspection after the trip showed grounding issues at weird places (seats, air compressor). Maybe do a voltage drop test and see if you have a poor ground possibly.

So even though the EVAP code hasn't popped up for awhile, I think I am going to replace it just to eliminate it, its cheap enough at least and i'm running out of things to replace or check.