I'm being beaten by this one...

Background: LR3 has the 4.4L V8. Truck has about 140K on it. Overall, no issues except this code that, upon clearing will reset on the second startup every time.

It would appear that this could be caused by low fuel pressure, an intake leak, or an exhaust leak. So, suspecting a leak before anything else, I've had the truck running at idle and, with a propane torch(unlit), began poking it all around the intake manifold and associated hardware on the top end. Never heard the truck change idle. I have not smoke tested it thinking that the propane test would ID any leaks. So, I'm assuming no intake leak at this point.

I then migrated to the exhaust and since the OBD code pointed to bank 1, I first replaced the downstream O2 sensor for no real reason beyond it was on Bank 1..No change nor did I really expect one. This was just throwing money away. So I sent air up the exhaust to bubble test the exhaust and started on bank 1 (passenger side for US truck). Exhaust manifold was leaking so I bought a new gasket and it still has a slight leak - getting a seal on this truck is a challenge. I also tested the driver side and it's leaking in the same place as the passenger side as well as the bung where the exhaust collector joins up to the cat. I reseated the clamp last night and also tightened down the manifold (bolt was loose) and tried driving the truck this AM. Same code.

I looked at the freeze frame data to look at short term and long term fuel trims and this is what it's coming up with:
STFT1: 8.6%
STFT2: 10.2%
TFT1: -4.7%
LTFT2: -5.5%
The freeze frame data was collected at a low RPM (679) so I'm assuming idle. Now that also makes me wonder about a leak on the top end knowing that with the throttle plate closed it would create some decent vacuum at idle.

To me it looks like STFT bank 2 over 10% would trigger the code, but I don't get why I'd get P2096 code for Bank 1??

I'm not ready to throw in the towel on this one yet, but if anyone has any ideas on troubleshooting it would be appreciated.

 

So........The wisdom of the internet says:

Long term and short term fuel trim should be as close to 0 as possible, and no more than +/- 10% - Your bank 1 trim average is: 3.9; Your bank 2 trim average is: 5........ This is good.

The total spread between long term and short term fuel trim should not be more than 10% - Your bank 1 spread is: 13.3; Your bank 2 spread is: 15.7......... these are bad.

The spread between the numbers vastly exceeds the "10% rule". It is true the total trim number is near zero and below 10%, but it's bad. It is an indication that the ECM is having problems keeping control of the fuel injection, it's scrambling to make up for an issue that is nearly out of its control. If the vehicle utilizes MAF, this condition STRONGLY suggests Mass Air Sensor issues.

For a suspected vacuum leak, note the fuel trims at idle and increase engine speed to 2500 RPM and hold. If the STFT immediately decreases and moves to acceptable levels and the LTFT slowly starts to come back down, you have a vacuum leak.

Might want to look at the MAF, If everything else seem good; I would try replacing the upstream 02 sensor.

Of course my general disclaimer applies: I could be wrong

Hope this helps

Jeff

 

Thanks Jeff,

I've been giving this a lot of thought and the info about the spread is really good. There is something there for sure. One thing that I struggle with, particularly with the MAF, is I would have expected it to have thrown the same codes for both banks. Same would have been true if there was an intake manifold leak after the MAF unless of course it was leaking maybe just over one particular cylinder of bank one...Has anyone else encountered a single bank code where it was MAF or general manifold leak?

I pulled the plugs this AM just to look at them. They all had a nice tan color and nothing to indicate anything different from one cylinder to the next. I did that because I was thinking maybe I have a bad injector and thought, if so, that I would see some sort of color variation. But nothing jumped out at me.

So, just analytically, I would have expected dual codes for both banks if I had a general problem vs. something really specific to Bank 1. Although since you pointed out that both have big spreads, it may just have been that Bank1 blow the threshold but Bank 2 isn't too far behind. So maybe that does point to a more general intake issue.

Any more insight would be appreciated. Thanks.

 

 

I also said Bank 1 upstream 02 sensor may be the problem, but that does not account for the wide fuel trend spread. Right side 02 sensors are easy to reach (compared to the left side)
If you replace the MAF and still get the code, try swapping the new 02 sensor into the upstream position.

WAIT... what year? I think there was a period of time that before, the sensors were different and after that date they were the same, but i do not remember the year (maybe 2007?)

Anyway keep us informed

Of course my general disclaimer applies: I could be wrong
Hope this helps

Jeff

 

The truck is an 07 Jeff. It is the year that LR transitioned to a different config on the O2 sensors so I can't swap upstream/downstream I can only do side to side but the driver's side is such a pain to get to with the driveshaft that I'm a little loathe to do it.

I think my next step is to do the propane test again but this time I'll watch the STFT and look for any changes. The last time I did it, I used my ear for any change to RPM but, from what I'm reading, the computer may be able to adjust so quickly that I may not hear any change to the way the motor runs. I'll chime in with how that goes.

As usual, if anyone has any additional insight - it's always appreciated!

 

Update: Still have the code.

I switched from propane testing the top end to smoking it and found the intake silencer box had several cracks after the MAF. I epoxied them but no luck, still throwing the code but I did stop the leask. I'm going to post the freeze frame data to see if anything jumps out at anyone because nothing really does to me. It looks like the issue is happening at idle, and possibly just as I'm stepping on the gas, but I'm not sure about the stepping on the gas part - I say that based on the pedal pos. values from the freeze frame data.

As always, any input is appreciated.

Fuel System Status: CL
Calculated Load Value: 50.6%
ECT: 71C
STFT-1:11.7%
LTFT=1:-2.3%
STFT-2: 9.4%
LTFT-2:-3.9%
Intake Manifold Pressure: 40.0 KPa
Engine RPM: 677
Vehicle Speed: 0
Ignitiion Timind Adv. 5.5degrees
IAT: 23C
Air Flow: 6.83 g/s
Abs. Throttle Pos: 13.7%
Time Since Engine Start: 238sec
Commanded EGR: 0.0%
EGR Error: 0%
Commanded Evap Purge: 32.5%
Fuel Level Input: 87.8%
Bar. Pressure: 99 kPa
Control Mod Volts: 13.81
Abs. Load Value: 23.1%
Fuel/Air Commanded Equivalence: 0.988
Relative Throttle Pos: 2.0%
Ambient Air Temp: 21C
Abs. Throttle Pos B: 31.0%
Accel. Pedal Pos D: 14.5%
Accel. Pedal Pod E: 14.9%
Commanded throttle Actuator Control: 20.4%

 

Since you sealed up the tube between the MAF and the throttle body only thing left is the throttle body (including the EGR valve) and the intake manifold itself.
Have you had the throttle body off recently? Maybe to change out the thermostat housing? Maybe that little silicone rubber washer between it and the intake manifold is leaking.
Most idle problems can be attributed to dirty throttle body, But I still think either MAF or upstream O2 sensor.
Try cleaning/inspecting the throttle body and gasket (no cost for parts) ans see if the off idle issue gets better.
Also is driving performance down? What is the fuel pressure? Is the Bar. Pressure of 99 kPa for the fuel?

We will stay with you until you spend all of your money buying parts to fix this. It is only common cutesy to so.
Seriously every fix we find on the forum is one less headache for the next person with the same problem.

I will keep digging with you until it is solved.

Jeff

 

Thanks Jeff, honestly I think the performance is not really noticeably affected. The truck seems pretty normal to me. The gas mileage might be down a bit, but I just drove it on a 6 hr highway ride and averaged 21.5mpg at 75mph and that's not too bad for this beast.

I did have the throttle body off in the early simmer and now you have me wondering about this silicone seal because I don't recall seeing one. I'll take it back off and make sure that it is still there. I'm honestly ready to replace the MAF and upstream O2 just because they are likely original and the truck does have 142K on it now. So it may not fix the issue but it really isn't that much to spend either.

I also went ahead and swapped both banks plugs and coils from side to side simply to eliminate the possibility of a plug not firing and pumping air. I was also tempted to swap fuel injectors from side to side too, but that would have taken more time than I had. No change after the plug/coil swap.

The Bar pressure is atmospheric pressure I believe.

I appreciate the input Jeff and anyone else with any ideas.

 

First, thanks for the thanks.

Second, Good that the deliverability is good. We may be able to no longer suspect the converters.

Change one thing at a time. Replace the MAF, clear the codes, and see what happens. If code comes back move to the O2 sensor. If not you found the problem.