2 lean banks and runs like crap


Siddhartha

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2000 3.0l flex fuel engine is throwing P0171 and P0174. Replaced MAF, Egr Valve, fuel filter, fuel pump, pov valve, o2 sensor S2B1, fuel injectors and have done a smoke test and still getting the codes and it runs worse everyday. STFT is at around 30 after it warms up a bit at idle I have bank 2 trim at +or- 7 and bank one is at 24 to 30. o2 sensors seem to be changing voltage as they should at 1hz or once every second. Downstream sensor takes some time to show any voltage used to sit at .7volts going up hill or underload, but it sits at .1 now. Could I actually have a clogged CAT? Any ideas? Thanks in advance
 


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Welcome to TRS,

Reads like a possible intake gasket leak. Do you have a way to get a vacuum gauge on it? The vacuum gauge readings can guide you towards a vacuum leak or clogged exhaust.
 

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Yes, Welcome to TRS :)

Passenger side is the issue, Bank 1, 30 STFT, thats O2 B1S1
So you shouldn't be getting P0174 any more?

O2 B1S2 would be the downstream O2

Downstream O2 should stay at about .7-.8volts once Cat is warmed up, and steady
If not and O2 is newer then could be bad Cat

O2 sensors read Oxygen Levels, .1v is High Oxygen(Lean), .9v is low oxygen(Rich)
The downstream Cat sees exhaust that should have most of the oxygen burned up as Cat cleaned the exhaust, so .7-.8volts
So its not actually "Rich" exhaust, the terms lean and rich don't really apply, they just use them to confuse DIY, lol
 

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Have you recently switched ethanol content?
 

Siddhartha

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Welcome to TRS,

Reads like a possible intake gasket leak. Do you have a way to get a vacuum gauge on it? The vacuum gauge readings can guide you towards a vacuum leak or clogged exhaust.
I changed the intake gaskets and vacuum pressure is 25in hg at idleand drop down at higher rpms. So I am leaning against vacuum leak, my fuel trims are all over the place.
 

Siddhartha

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Have you recently switched ethanol content?
Nope, use the same fuel from Safeway or the
Pilot station. That ethanol switch is an expensive bugger. We don't have to much ethanol in the NW.
 

Siddhartha

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Yes, Welcome to TRS :)

Passenger side is the issue, Bank 1, 30 STFT, thats O2 B1S1
So you shouldn't be getting P0174 any more?

O2 B1S2 would be the downstream O2

Downstream O2 should stay at about .7-.8volts once Cat is warmed up, and steady
If not and O2 is newer then could be bad Cat

O2 sensors read Oxygen Levels, .1v is High Oxygen(Lean), .9v is low oxygen(Rich)
The downstream Cat sees exhaust that should have most of the oxygen burned up as Cat cleaned the exhaust, so .7-.8volts
So its not actually "Rich" exhaust, the terms lean and rich don't really apply, they just use them to confuse DIY, lol
My bank 2 o2 sensor takes forever to show a signal, then will usually just show .1v or .9v then will actually act "right" after around 20min. Starting to think I have an issue like a short of the heater circuit, and the ECM is compensating by dumping fuel when it should be cutting fuel. Testing my o2 circuits this afternoon.
 

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I've also measured the temp on my cat and they seem to be in working order.
 

RonD

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Each O2 Heater circuit is monitored so you would get a code if it was the problem

Have you changed the B2S1 O2 sensor?
If not do so, if you have then swap it around with either other O2 and see if problem follows O2(faulty O2) or stays at bank 2(wiring issue)
 

Siddhartha

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So my battery died, I disconnected the battery while I charged it. Think my 5yo battery is going bad. Changed B2S1 a couple weeks ago, for same issue. While over analyzing stuff and looking at trims and watching some videos, I learned that the ECM will compensate for a bad o2 by using the trim values from the "known good sensor". That sensor isn't getting hot enough. Found a historical code for heater circuit B2S1. Even after clearing KAM it didn't take long once the system went closed loop to start compensating. Now I have to check for bad wire. Or 2. Think that a slowly heating o2 sensor has been causing all of my confusion. Just wish my arms were thinner and longer so that I could back probe the wires easier.
 

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All 3 O2 heaters get 12volts from fuse #13 in engine fuse box, they share common wire from this fuse

Each has a separate Ground wire that runs to the computer, thats how the computer can monitor if heaters are working, if no 12volts thru the heater then it would set a code for that one O2, or 3 codes if fuse was blown
i.e.
Upstream
P0135 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P0155 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1) <<<<<
Downstream
P0141 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

The connector for the drivers side O2 would be where to check for 12v and ground, unplug it
Key on activates heater 12volts and computer's Ground for the heater
In 2000 should be light blue/orange stripe wire for 12v and yellow/blue for ground on that one O2, maybe
 

Siddhartha

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All 3 O2 heaters get 12volts from fuse #13 in engine fuse box, they share common wire from this fuse

Each has a separate Ground wire that runs to the computer, thats how the computer can monitor if heaters are working, if no 12volts thru the heater then it would set a code for that one O2, or 3 codes if fuse was blown
i.e.
Upstream
P0135 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P0155 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1) <<<<<
Downstream
P0141 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

The connector for the drivers side O2 would be where to check for 12v and ground, unplug it
Key on activates heater 12volts and computer's Ground for the heater
In 2000 should be light blue/orange stripe wire for 12v and yellow/blue for ground on that one O2, maybe
I'll just check the pins for the 2 white wires, black is the signal grey gnd as the corresponded to the plug. I did have a 155 code a couple weeks ago.
 


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